Review Article Advances in Miniaturized Instruments for ...

Review ArticleAdvances in Miniaturized Instruments for Genomics

Cihun-Siyong Alex Gong12 and Kin Fong Lei34

1 Department of Electrical Engineering School of Electrical and Computer Engineering College of EngineeringChang Gung University Taoyuan 333 Taiwan

2 Portable Energy System Group Green Technology Research Center College of EngineeringChang Gung University Taoyuan 333 Taiwan

3Graduate Institute of Medical Mechatronics Chang Gung University Taoyuan 333 Taiwan4Department of Mechanical Engineering Chang Gung University Taoyuan 333 Taiwan

Correspondence should be addressed to Kin Fong Lei kfleimailcguedutw

Received 18 December 2013 Revised 21 January 2014 Accepted 30 January 2014 Published 29 May 2014

Academic Editor Tzu-Chen Yen

Copyright copy 2014 C-S A Gong and K F Lei This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

In recent years a lot of demonstrations of the miniaturized instruments were reported for genomic applications They providedthe advantages of miniaturization automation sensitivity and specificity for the development of point-of-care diagnostics Theaim of this paper is to report on recent developments on miniaturized instruments for genomic applications Based on the maturedevelopment of microfabrication microfluidic systems have been demonstrated for various genomic detections Since one of theobjectives of miniaturized instruments is for the development of point-of-care device impedimetric detection is found to be apromising technique for this purpose An in-depth discussion of the impedimetric circuits and systems will be included to providetotal consideration of the miniaturized instruments and their potential application towards real-time portable imaging in the ldquo-omicsrdquo eraThe current excellent demonstrations suggest a solid foundation for the development of practical and widespread point-of-care genomic diagnostic devices

1 Introduction

Genomics has become an important part of our life sinceits name was established in the latter half of the twentiethcentury It was derived from genetics which includes ldquoclassicrdquoand ldquomolecularrdquo as a whole Polymer chain reaction (PCR)technique is a gold standard for clinical genomic diagnosisNormally the concentration of genomic sample is too low forgenerating detectable signal PCR can amplify a few copiesof DNA to millions of copies of a particular DNA sequenceThe technique relies on thermal cycling that is repeatedheating and cooling of the reaction for DNA melting andenzymatic replication of the DNA Generally twenty to fortythermal cycle times are involved and they take several hoursto complete Although this technique is sensitive for genomicdetection it is time consuming and labor intensive limitingthe throughput of the diagnosis

In order to enhance the efficiency of the biological reac-tion reduce the usage of reagent and sample and eliminatethe fault by human handling miniaturized instruments thathandle small quantity of fluid for example microliter ornanoliter were proposed for the next generation of thediagnostic equipment Such instruments are also named asmicrofluidic systems lab-on-chip (LOC) devices biochipsor micrototal-analysis systems (120583TAS) Because fluid in smallamount is manipulated in microscale environment one ofthe important properties is to highly enhance the surface-to-volume ratio of the fluid For some specific applications highsurface-to-volume ratio can benefit the process efficiencyFor example DNA hybridization in rapid diagnostic devicenormally involves a solid support for the immobilization ofthe reactants that is probe DNA strands The counterpartof the reactant that is target DNA strands is introducedto the site for binding reaction The binding efficiency is

Hindawi Publishing CorporationBioMed Research InternationalVolume 2014 Article ID 734675 13 pageshttpdxdoiorg1011552014734675

2 BioMed Research International

based on the collision possibility Because of the reductionin diffusion distance and increase in surface-to-volume ratioin microfluidic environment the reaction kinetics of DNAstrands binding reaction was shown significantly acceleratedcompared with the conventional microplate technique [1ndash5] That results in greatly improving the response time ofthe biological reaction and the sensitivity of the biologicaldetectionMicrofluidic system is often interpreted to aminia-turized version of bioanalytical laboratory It can perform theentire analytical protocol such as sample preparation reagentapplication biological reaction and detection automaticallyto eliminate the handling fault Since microfluidic system isa miniaturized instrument portability is realizable for thepoint-of-care diagnostic applications

The aim of this paper is to report on recent developmentson miniaturized instruments for genomic applications Anoverview of microfluidic systems and their demonstrationsfor genomic diagnosis will be discussed Moreover impedi-metric detection is found to be a promising technique forpoint-of-care genomic detection because the impedimetricsignal can easily be analyzed by miniaturized electricalcircuits In-depth discussion of the consideration and reviewof impedimetric circuits and systems will also be included inthis article

2 Miniaturized InstrumentsMicrofluidic Systems

In the past decade development of the microfluidic tech-nology becomes intensive and many research articles areavailable [6ndash11] The fabrication of microfluidic systemswas originally based on the silicon fabrication technologyfrom semiconductor and microelectromechanical systems(MEMS) Silicon microfabrication is well established butsilicon material is not optically transparent and is electricallyconductive Hence it is not appropriate for the biomedicalapplications For example the microfluidic system for cellculture is required to be transparent for continuous opti-cal monitoring of cell morphology Moreover microfluidicsystem for glucose detection is based on electrochemicalreaction which needs insulated substrate for measurementTherefore silicon may not be an appropriate material whenoptical and electrochemical detections are adopted in themicrofluidic systems Therefore glass and polymeric mate-rials were used because they are less expensive opticallytransparent and not electrically conductive Specific fab-rication technologies for microfluidic systems were intro-duced such as soft lithography hot embossing and substratebonding techniques Soft lithography represents a nonpho-tolithographic strategy based on self-assembly and replicamolding for carrying out micro- and nanofabrication [12]An elastomeric stamp with patterned relief structures onits surface is used to generate patterns and structures withfeature sizes ranging from 30 nm to 100 120583m It provides aconvenient effective and low-cost method for the forma-tion and manufacturing of micro- and nanostructures Hotembossing technique is for mass production of plastic micro-components [13] A mold with microstructures is pressed

into a thermoplastic polymer film heated beyond its glasstransition temperature under vacuum After cooling downthe microstructures can be transferred from the mold to thepolymer film To fabricate a functional microfluidic systemsubstrate bonding is an important process and adhesionbetween substrates is a problem of great practical concernThermal compression ultrasonic or gluing by application ofeither epoxy or methanol may induce global and localizedgeometric deformation of the substrates or leave an interfaciallayer with significant thickness variation Therefore specialbonding processes for glass and polymeric materials havebeen developed for fabricating microfluidic systems [14ndash17] Localized welding of polymeric materials embeddedmetal films located between the desired bond surfaces bymicrowave energy has been developed [15] The bonding canbe achieved with 10Wmicrowave power in 120 s

Based on the mature development of the fabricationtechnology a board spectrum of biological analytical appli-cations has been demonstrated using microfluidic systemssuch as DNA analysis [1 18ndash24] immunoassay [25ndash31]and cell analysis [32ndash38] For example immunoassay oncompact disc (CD) has been demonstrated and fluids inCD were manipulated by the centrifugal forces controlledby the rotational speed of the CD [30] Illustration andphotograph of the CD-based microfluidic system are shownin Figure 1 High throughput screening of analytes couldbe realized by simultaneous functions in parallel layoutson the CD Enzyme-linked immunosorbent assay (ELISA)was demonstrated on this CD-based platform Anotherexample is to construct a microfluidic chip for real-time andnoninvasive impedimetric monitoring of cell proliferationand chemosensitivity in three-dimensional (3D) cell cultureconstruct as shown in Figure 2 [37] Human oral cancercells (OEC-M1) were encapsulated in 3D agarose scaffoldand cultured in a miniaturized chamber under perfusionof tested substance This setting provides a more in vitrophysiologically relevant microenvironment to better mimicthe complex in vivo microenvironment These excellentdevelopments showed the capability of microfluidic systemfor performing complex analytical applications Commercialpossibility is obvious because the microfluidic system canprovide a total solution of biological analysis from the sampleapplication to the display of the analysis results Point-of-care diagnostic applications can be realized based on theadvantages ofminiaturization integration and automation ofthe microfluidic system

3 Integrated Microfluidic Genomic Systems

Microfluidic systems have been also applied to the genomicapplications System integrated with microchannels heaterstemperature sensors and fluorescence detectors was fabri-cated for the functions of capturing DNA mixing solutionsamplifyingDNA and separating and detecting of those prod-ucts [20] These complicated operations could be performedon a single glass and silicon substrate Strand displacementamplification experiment was conducted and showed that thespecific target DNA was successfully amplified and detected

BioMed Research International 3

(a)

1

2

3

4

5

6

7

8

9

10

11

(b)

7mm

(c)

Figure 1 Schematics of (a) a CD-ELISA design with 24 sets of assays (b) a single assay and (c) photo of a single assay Copyright 2004Reprinted from [30] with permission from the American Chemistry Society

Fluidic layer

Culture chamber layer

Electrode layer

Perfusion path

3D culturechamber

Vertical electrodeElectrical contact

(a) (b)

3D culture constructPerfusion path

Fresh medium

Syringe pumpVertical electrode

Impedance analyzer

Spent medium

(c)

Figure 2 (a) Design of the microfluidic chip (b) Photograph of the microfluidic chip (c) Illustration of the experimental setup of theperfusion 3D cell culture incorporated with on-site impedance measurement Copyright 2014 Reprinted from [37] with permission from theElsevier

Moreover PCR is a widely used technique in biologicalapplications and was implemented on a microfluidic systemas illustrated in Figure 3 [39] The PCR was achieved byintroducing the reactant droplet into the inletThree reactionchambers respectively stabled at 90∘C 72∘C and 55∘C wereintegrated in a chip and droplet was driven back and forth bythree piezoelectric micropumps between these three reactionchambers After 20ndash30 thermal cycles the PCR productswere pumped into the reservoir to be collected and analyzed

by gel electrophoresis Also an electrokinetically controlledDNA hybridizationmicrofluidic chip has been demonstratedand can perform all processes from sample dispensing tohybridization detection within 5 minutes [1] The chip con-sisted of a PDMS upper substrate and a lower glass substratethat served as a substrate for the hybridization array asshown in Figure 4 The design of the chip was an H-typechannel structure containing immobilized single-strandedoligonucleotide probes The electroosmotic pumping could


ZOutlet hole

Inlet hole

Pyrex wafer

Section line

Silicon wafer

Heat sink

Pt temperaturesensor

pn-diode

Pt heaters

Optical fiber pn-diode

Reactionchambers

90∘C

72∘C

55∘CX

Optical fiber

Pyrex

Silicon

PZT disc

PZT disc

Connection channel

Cr membranePump structure from cross sectional area Z-Z998400

Y

Connection channel

between pump andreaction chamber

Connection channel between pumpchambers

Section lineX-X998400 forX998400

Z998400

Wirebonding

hole

Etched pumpmembrane

ermalisolation

recess

Y998400

Figure 5(a)

Y-Y998400 for Figures5(d) 5(e)

Figure 3 Schematic of the pump PCR chip For simplification the upper glass wafer and the lower silicon wafer are illustrated apart althoughin the actual device both wafers are connected by anodic bonding The lower left insert figure shows an expanded view of the reactionchamber and the lower right insert shows the cross-section of the micropump Copyright 2003 Reprinted from [39] with permission fromIOP Publishing Ltd

dispense the controlled samples of nanoliter volume directlyto the hybridization array and remove nonspecific adsorp-tion Hybridization washing and scanning procedures canbe conducted simultaneously Detection levels as low as50 pM were recorded using an epifluorescence microscope

4 Impedimetric Detection of Genomic Signal

In conventional genomic detection optical measurement forexample fluorescent labeling technique was utilized to quan-tify the genomic activity for example DNA hybridizationand PCR product But this measurement technique is timeconsuming and labor intensive Alternatively impedimetricdetectionwas proposed to be one of the promising techniquesto quantify biological activity in the microfluidic systemsThe detection results are represented by electrical signalswhich can easily interface with miniaturized instrumentsFor example electrical detection of DNA hybridization usingelectrochemical impedance spectroscopy (EIS) was demon-strated [40] Results showed a 25 increase of impedancefor double-stranded DNA on gold electrode compared withthe same electrode with immobilized single-stranded DNAAnother example showed that the DNA hybridization could

be detected by the resistance change across the electrode[41 42] DNA hybridization on a pair of electrodes wasindicated by gold nanoparticles and the gold nanoparticleswere physically amplified to a silver conductive layer onthe electrode The hybridization result could be measuredby the conductivity changes across the electrode Thesedemonstrated showed an alternative method for detectingthe genomic signal For the application of cell proliferationstudy the entire process requires a long period of timeand in a controlled environment It is more preferable toperform in a bench-top system However a miniaturizedand portable device is more preferable for the on-site rapiddiagnostic application The combination of microfluidic andimpedimetric technologies would be suitable for such aspecific application

5 Impedimetric Foundation

As mentioned the impedimetric method provides a versatileway that can be used for many biological applications includ-ing the quantification of genomic activity and the noninvasivemonitoring of cell proliferation and chemosensitivity with amicrofluidic chip The underlying principle of the technique


PDMS microfluidicsystem

Glass substrate withhybridization array

(a)

8mm

30mm

120120583m

5mm

65120583m Probe site

R = 2mm

1

2

3

4

(b)

Figure 4 (a) Assembly procedure for PDMS fluidics and immobilized hybridization array (b) H-type channel structure for DNAhybridization chip (1) sample port (2) auxiliary port (3) buffer port and (4)wash port Copyright 2004 Reprinted from [1] with permissionfrom the American Chemical Society

Variable-frequencycurrent source

IS(t)

IS(t)

t t

(+)

(minus)

(+)

(minus)

SUTVS(t)

lowastDetermine amplitudelowastDetermine phase

Figure 5 The basic model of equivalent circuit used to elaborate on the relation of sample under test (SUT) to the generated current sourceand resulting voltage response

can be explained from Figure 5 Let us assume for the sakeof simplicity that the sample under test (SUT) consists onlyof a resistor that is connected with two electrodes The upperelectrode is commonly called ldquoanoderdquo or ldquoworking electroderdquoThe lower electrode is called ldquoauxiliary electroderdquo functioningas ldquocathoderdquo Tounderstand SUT an active alternating current(AC) 119868

119878(119905) is generated and injected into the close loop

The resulting voltage drop across the two electrodes can bemeasured to derive the resistance of SUT by means of Ohmrsquoslaw provided that both the two electrodes have zero voltagedrop When the equivalent circuit of electrode becomes acomplex number as the combination shown in Figure 6(a)variable-frequency current source is required to draw so-called ldquoNyquist plotrdquo (Figure 6(b)) [43] The model shownin Figure 6(a) is based on electrochemical point of view Itis consisted of an ohmic resistance 119877

119900stemming from the

solution resistance and electrode geometry a charge transferresistance119877ct stemming from the charge transfer between theinterface of electrode and electrolyte an electric double-layercapacitance 119862

119889stemming from placing a large-area charge in

the electrolyte in proximity to that on the porous electrodesat the medium-frequency region a Warburg impedance 119885

119908

representing the mobility of the internal ions resulting fromthe diffusion and migration at the low-frequency region andan electrode inductance 119871

119889stemming from reduction in the

penetration depth of the ions at the high-frequency regionrespectively [43 44] As a matter of fact with regard tothe ohmic resistance of SUT an electrode immersed into anelectrolyte creates a potential that is related to the oxidation-reduction concentration according to the Nernst law [44]The corresponding potentials cancel out as long as the twoelectrodes are the same Unfortunately this would never


R0

Rct

Ld

Zw

Cd

(a)

Mass transport

Electric and magnetic

Double-layer

mHzf

Ro + Rct

ReZkHz HzRo

minusImZ

(b)

Figure 6 (a) Schematic of the equivalent circuit of electrode in an electrochemical point of view (b)The so-called Nyquist plot showing thecharacteristic of frequency response versus the decomposition of impedance

happen and a potential difference of a few millivolts wouldalways exist between SUT and either of the electrodes [44]

6 Impedimetric Consideration

There have been several technically sound circuits andsystems demonstrated in the literature to implementthe impedimetric method so far [44ndash49] They are similarto a coherent demodulation technique demonstrated inFigure 7 where a four-electrode method was adopted[45] The impedance sensing method shown in Figure 5is premised on the assumption that both working andauxiliary electrodes have resistance value of ldquozerordquo Howeveras mentioned this would never be the case and there existvoltage drops of them in the close loop as soon as an electricalcurrent flows through turning out that certain inversionformula is unavoidable for derivation of the ohmic resistanceof SUT This may be taxing on postprocessing and result inincapability of real-time impedance monitoring By takingthe advantages of the advances in modern semiconductortechnologies an amplifier with ultrahigh input impedance(almost open circuit) can be readily available In additiondifferential sensing is always a better choice than the single-ended counterpart as a result of better noise immunity[46 50] These form the foundation of the architectureshown in Figure 7

7 Circuits and Systems forBioimpedance Measurement

Referring to Figure 7 in addition to the necessary electrodesZe1 and Ze4 to form a loop two additional electrodes Ze2and Ze3 were added and combined with the instrumentationamplifier (IA) whose common-mode rejection ratio (CMRR)

VCO

Demodulator

Demodulator

ADC

ADC

Ze1Ze2

Ze3Ze4

SUT IA

Re

Im90∘

0∘

+

minus

Figure 7 Impedance sensing architecture presented in [45] withwhich the four-electrode method accompanies demonstrating thecoherent demodulation technique

is significantly improved as compared with the ordinarycounterpart [45 46] The variable-frequency sinusoidal cur-rent used for sensing was generated by a dedicated voltage-controlled oscillator (VCO) Thanks to the high-impedancefeature of the amplifier there was no current flowing throughZe2 and Ze3 As a result the sensed voltage drop acrossSUT has predetermined current and therefore can be usedto represent the impedance of SUT A system with this kindof 4-electrode configuration is also known as a system usingldquotetrapolar methodrdquo [48]

To decompose the complex number of impedance twoorthogonal AC signals are required in the coherent demod-ulation based on the Eulerrsquos formula to represent a peri-odic signal using a combination of sine and cosine TheAC signals were generated in the same VCO to reducethe system complexity and save the implementation costThe Demodulator circuits functioned as ldquomixerrdquo and theiroutputs were quantized by the dedicated analog-to-digital


ΔV

Input buffer Differential amplifier

Vout+

minus

R4

R4

R3

R3

R2

R2

R1

VNVB

VA VMA1

A2

IR1 A3

+

minus

+

minus

(a)

CM1

CM2

RG

VoutR1

VY

VX

VG

VB

VA

IR1

A1+

minus

A2+

minus

+

minusA3ΔV

I2

I1

IG = I1 minus I2 = 2IR1

I1 minus I2

(b)

Figure 8 (a)The circuit schematic of conventional instrumentation amplifier (IA) in [50] (b)The circuit schematic of improved counterpartin [51]

converters (ADCs) The real part (Re) and imaginary part(Im) can be used to drawNyquist plot for impedance analysisIt should be noticed that practically there still exists certainelectric potential difference between Ze2 and Ze3 in spiteof the zero current at the inputs of IA and due to that Ze2and Ze3 could not be identical As a result high CMRR isnecessary to reject the potential difference of IA resulting indesign challenge The major bottleneck in implementation isthe matching of resistors involved in the commonly adoptedIA structure shown in Figure 8(a) [50] where the output of IAcan be expressed as

119881out = minus1198774

1198773

(1 +21198772

1198771

) (119881119860minus 119881119861) = 1198701(119881119860minus 119881119861) (1)

Achieving sufficient resistive matching between 1198774and

1198773(or 1198772and 119877

1) to obtain high CMRR relies on post-IC-

fabrication trimming which is cost ineffective and difficultto fulfill miniaturization in practice As a result the designshown in Figure 8(b) was proposed [51]Themost significantfeature of the design is that it requires only two resistors1198601and 119860

2form source followers as conventional thereby

forcing 119881119860= 119881119883and 119881

119861= 119881119884 The current flowing out of 119860

1

and that of1198602are equal but they have opposite polarities By

using a current subtractor marked in the dotted line one canobtain 119868

119866= 21198681198771 hence the output of IA becomes

119881out =2119877119866

1198771

(119881119860minus 119881119861) = 1198702(119881119860minus 119881119861) (2)

This circuit structure successfully alleviates the impactof mismatched resistance achieving both high CMRR andminiaturization at the cost of increased power consumptionas compared with that shown in Figure 8(a) High CMRR canalso be attained by means of considerably increased differ-ential gain Unfortunately the energy efficiency of system isfurther compromised

An often overlooked factor in correct impedance mon-itoring is that the electrode-referred DC offset (ERDO)limits the available CMRR affecting the operation of IA

and degrading overall performance no matter how goodthe following circuits and systems can be Two renownedtechniques have been proposed so far to cancel ERDO Atechnique called ldquoautozeroingrdquo is shown in Figure 9(a) [52]It uses three switches to cancel ERDO 119881OS When 120601 is ata logic-ldquohighrdquo level the amplifier involved samples 119881OS andstore them on 119862

119878 Assuming that the open-loop gain of

amplifier is119860 the voltage on 119862119878will be119881OS sdot (119860(1+119860)) after

settling When 120601 becomes a logic-ldquolowrdquo level119881OS of previousstate will be subtracted from 119881

119894which is superimposedwith

current 119881OS which will be with the same value as that ofprevious state resulting in a considerably decreased ERDOof119881OS sdot (1(1 + 119860)) present at the positive terminal of amplifierThe autozeroing technique can also effectively reduce theldquoFlickerrdquo noise of modern semiconductor process but comeswith a penalty of high-frequency interference stemming fromthe sampling clocks of the switches Its major drawback is thewide bandwidth of amplifier as a result of the voltage settlingon 119862119878

Another efficient candidate is the work shown inFigure 9(b) where 119881ip and 119881in can be connected with Ze2and Ze3 respectively The circuit serves as a preamplifierlocated between the electrodes and IA to ldquocontinuouslyrdquoremove ERDO [53] Here we use single differential circuitconfiguration to detail its advantage but then it can turninto its fully differential counterpart to provide two outputterminals to IA The design embodies the AC coupling toreject ERDO in order to make itself free from malfunctionas a result of the saturation The low-frequency cutoff ofthe high-pass filter formed by the 119877

2-1198622network can be

adjusted through their time constant The low-pass cornerfrequency can be adjusted by the time constant of the lumpedimpedance at the output of the preamplifier and119862

119871 Owing to

the low frequencies required by the impedancemeasurementan extremely large 119877

2-1198622time constant is unavoidable As a

result a pseudoresistor configuration shown in Figure 9(c)can be adopted [53] The pseudoresistor operates the transis-tors involved at ldquosubthresholdrdquo operation to achieve a largeequivalent resistance value that is almost impossible to be


Vo

Vi

CS

120601

120601

120601

++

minus

minusminus

VOS

(a)

C2

C2

R2

R2

C1

C1

Vout

Vin CL

Vip

+

minus

(b)

VbVa

0

R

1GΩ

1MΩ

Vba

(c)

Figure 9 (a) The autozeroing technique [52] (b) The AC-coupled technique [53] (c) The pseudoresistor technique [53]

realized on the basis of ldquoon-chiprdquominiaturizationThe closed-loop midband gain of the preamplifier can be determined by11986211198622

It should also be noticed that the accuracy of current ofmeasurement signals generated from VCO for the demod-ulation and how accurate their frequencies and phases canbe achieved by the system shown in Figure 7 will also affectthe final outcome dramatically The frequencies and phasescan be adjusted and finely tuned by means of a phase-locked loops with a precise reference frequency [54] Sucha frequency can be generated from an electronic circuit con-taining a mechanically resonant vibrating crystal (so-calledcrystal oscillator) [54] Precise current of measuring SUTcan be obtained through the use of a ldquocurrent mirrorrdquo withsufficiently high output impedance Modern semiconductortechnologies offer many well developed and miniaturizedcircuit topologies to achieve such a goal [55 56]

To advance miniaturization the architecture shown inFigure 7 could be further improved as the complexity-reduced alternative shown in Figure 10 [48]The architecturewhich is called synchronous sampling has mainly two most

significant features (a) removal of IA and (b) representingfinal results in pulse-width modulation (PWM) (using aone-bit ADC) The elements 119885EA to 119885ED correspond to theimpedance of the four electrodes and the media were mod-eled by the elements 119885MA to 119885MD Each of these impedanceshas real and imaginary components associated with the con-ductivity and dielectric properties of the media respectively[48] The voltage on the negative terminal of OTABIAS willbe forced to become the reference voltage 119881ref which was setto halve the supply voltage and was used as the ldquogroundrdquo inthe analog circuits involved thanks to the high open-loopgains of the amplifiers achieving the ldquovirtual shortrdquo It turnsout to be reducing the loss in the parasitic elements and avoid-ing the need for IA and the differential AC-coupled inputsThe demodulated results followed by the low-pass filter(LPF) were compared with 119881ref to obtain a PWM waveformthat is easy to be transmitted wirelessly without parallel-serialconverter commonly seen at the output of ADC for seriallink This architecture avoids two demodulation channelsby incorporating a sampling mechanism using the propersampling times


intVref

Vref

LPF

Digital control

sgn[cos(120596t)]sgn[cos(120596t + 1205872)]

1

1

2

3

minus1

HPFOTABuf

OTABias

DAC

cos(120596t)

cos(120596t + 120587)

sim

sim

Current excitation Media Electr

A

B

C

D

ZMA

ZMC ZMD

ZMB

ZEA

ZEB

ZEC

ZED

Voltage sensing circuit coherent detector

+

minus

+

minus

Figure 10 Synchronous sampling impedance sensing architecture Copyright 2009 Reprinted from [48] with permission from Elsevier

+

minus

+

minus

Vo

Vod

Vxd

V120601

EXOR

IA

AC

DCEA

OTA

120572ia

Rectifier

120572dc int

+

minusint

+

minus

VS120572ea

Vm

Zx

K

Gm

gm

Vx

e1

e2

ix

Vdc

Vref

Current oscillator

ixo middot sin(120596t)

Figure 11 The closed-loop impedance sensing architecture Copyright 2010 Reprinted from [49] with permission from Elsevier

Recently a closed-loop architecture shown in Figure 11was proposed [49] Despite the same theory principle forimpedance measurement its target used to determine thefinal outcome is unlike the two representative architecturesshown in Figures 7 and 10 In this design the resulting voltageacross the impedance under test (ZUT) including SUTwill beconfined to a predetermined amount using the error amplifierEA with the given reference voltage 119881ref at its input This willhelp to operate the electrodes involved in a linear and pre-dictable regionThe generated AC current 119894

119883flowing through

ZUT can be controlled timely as a result of the feedback loopat 119881119874 Because the transconductance of OTA (119892

119898) can be

deduced during design and measurement phases and boththe multiplication factor119870 and signal source119881

119878can be given

119894119883can be obtained provided that 119881

119898is available after being

monitored With 119881119883

and 119894119883 the impedance ldquomagnituderdquo

of ZUT can be measured The impedance ldquophaserdquo can be

measured by comparing the digitized results 119881od and 119881xd of119881119874and the output of OTA to each otherAlthough the architecture shown in Figure 11 provides

a good candidate to achieve not only an operation takingthe contribution of electrodes into account but also a safemeasurement with a decent accuracy as compared withothers demonstrated in the literature its overall performanceis governed by the bandwidth open-loop gain input offsetand CMRR of amplifier similar to its counterparts Howeverhigh-gain wide-bandwidth low-offset and high-CMRRamplifier consumes considerable power consumption whichgoes against portability requiring miniaturization In a nut-shell it has been believed that the performance of analog frontend is of primary importance for the precise measurementof impedimetric system The miniaturization effort involvesmaking trade-offs among different aspects of mixed-signal(analog and digital) circuit design The technical strategies


Counter electrode

Trapped

CTC cells

Gold microelectrode

arrey 20 times 20120583M Si substra

te integrated circuits

(a) (b)

(c)

(d)

Top counter electrode

ElectrolyteCell

Electrode 1 Electrode 2

Micro controller for electrodeselection (linecolumn decoder)

Electro impedance spectroscopy(EIS) measurement unit

Processing unit-signal synchronization and data

acquisition

Figure 12 CMOS based sensor array for cell counting (a) Schematic of the microelectrode arrays for the cell detection (b) Illustrationof the sensor layout and the addressing scheme employed in the CMOS sensor chip (c) CMOS chip packaged with a switching PCB (d)Microphotograph ofmore than nine thousand electrodes in a single chip Copyright 2012 Reprinted from [57] with permission from Elsevier

illustrated with Figures 8 and 9 are by no means the totalsolutions but have demonstrated that they can be usedto effectively deal with the mentioned problems in termsof miniaturization point of view Last but not least withregard to some implantable applications where an extremelyminiaturized design of real-time impedancemonitoringmustbe fulfilled in limited space to allowing integration to themostdegree the test current of SUT and ZUT could be generatedby an electrical stimulator without the dedicated circuit suchas VCO DAC or current oscillator shown in Figures 7 10and 11 respectively [56 58 59] This turns out to be goodfor the system on a chip (SoC) in modern semiconductortechnologies

8 Impedimetric Imaging Instrumentationin Omics

We have reviewed in detail the technologies regardingminia-turization One might want to know the relevance betweenthem and ldquoimagingrdquo For the delivery of next-generationtherapies functional characterization of genes using a sys-tematicway is imperativeOne of themanners doing this kindof characterization requires downregulation of the expression

of specific genes in order to comprehensively study thefunctions of genes [60] To this end the cell-based functionalassay has been emerged as one of the powerful tools foracute observation [61] The cell-based functional assay canbe used to acquire the information about the phenotypiceffect of targeted ldquogene knockdownrdquo which is a technique toreduce the expression of one or more of an organismrsquos genesin a way ldquoincisiverdquo when using RNA interference (RNAi)[62] However almost all of the assays are used only forexperiencing a rapid onset (ie to say ldquofor a given pointof timerdquo) currently implying that most of the changes aremissed in measurement In addition it has been demon-strated that advanced state-of-the-art electronic biosensorswith microwell plates should be developed to be able torecord impedimetric cell-to-electrode responses in a wayldquolabel-freerdquo by means of microelectrodes The combinationof the requirements ldquocontinuous monitoringrdquo ldquoimpedimet-ric cell-to-electrode recordingrdquo and ldquobidimensional-space(2D) electrode array manipulationrdquo form the base of new-generation time-dependent profiling for cell responses Oneof the most recent works with respect to the development ofimpedimetric spectrum platform with different applicationregarding cell has been demonstrated in Figure 12 whereadvanced semiconductor process and circuit techniques have


been employed to advance miniaturized sensing systemwith light weight and low power in the platform [57] Bydisplaying the results of 2D spectrum continuously real-timeimpedimetric imaging can be realized to ceaselessly measurethe cell status of importance

9 Concluding Remarks

The ever increasing demand in the modern technologieshas improved the quality of life Microfluidic systems havebeen applied to different genomic applications and showedrealizable opportunity for point-of-care diagnostic devicesThe advances in circuits and systems have been drivinga technical revolution in the microfluidic systems that areessential to the ldquo-omicsrdquo era Impedimetric detection is apromising technique to develop miniaturized measurementequipment The improved impact on the SoC techniques hasenabled sustainable solutions which have been demonstratedso far to be effective to pressing real problems in such afield Several representative solutions ranging from impedi-metric architectures and efficiency-enhanced miniaturizedtechniques have been discussed in detail in this paper Manyresearchers have pursued the ideas of using the techniquesthey have learned to facilitate interdisciplinary collaborationsamong SoC design micromechanical technologies materialscience and biomedical engineering It is almost impos-sible to embody miniaturization towards light weight andlow power while at the same time achieving an accurateimpedance signal conditioning and the reduced responsetime without the help of microfabricated and mixed-signaltechnologies not to mention the portability In addition tothe applications and advantages mentioned it can be envi-sioned that by leveraging the architectures and techniqueslow-price and precise early detection of many fatal diseasessuch as the cancers will eventually come true Despite thestrength and importance of impedancemeasurement systemthose prior arts suffer the most from the contamination ofelectrode Once the electrodes dip into the sample non-specific adsorption of biological components starts to takeplaceThe contamination of electrode is still an open questionand is accompanied with distortion of measured impedancespectrum resulting in observable (inductive) artifact at somefrequencies In order to eliminate the contamination of detec-tion electrodes and reaction chamber the device is normallydesigned to be disposable for the rapid diagnostic applica-tions Moreover the electrodes are made of noble metals forexample Au and Pt in order to prevent the surface oxidationThe contamination may also be overcome by having alarge number of in vitro tests on electrode-sample reactions(redox) as an index of lookup stored in an on-chip memoryThis may greatly help differentiate the shifted impedancespectrum from its normal circumstances (through somekinds of algorithms) In conclusion the microfluidic systemsincorporated with impedimetric detection technique providesimple miniaturized and sensitive detection of genomicsignal It is believed that these systems can develop practicalpoint-of-care genomic diagnostic devices

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This study was supported in part by the National ScienceCouncil (NSC) Taiwan under Grant no NSC 102-2218-E-182-003- The authors would also like to thank fundingsupport from the Chang Gung University Taiwan andChang Gung Memorial Hospital Taiwan under Grants nosUERPD2D0011 CMRPD2C0141 and CMRPD2D0021

References

[1] D Erickson X Liu U Krull and D Li ldquoElectrokineticallycontrolled DNA hybridization microfluidic chip enabling rapidtarget analysisrdquo Analytical Chemistry vol 76 no 24 pp 7269ndash7277 2004

[2] P K Yuen G Li Y Bao and U R Muller ldquoMicrofluidic devicesfor fluidic circulation and mixing improve hybridization signalintensity on DNA arraysrdquo Lab on a Chip vol 3 no 1 pp 46ndash502003

[3] R H Liu R Lenigk R L Druyor-Sanchez J Yang andP Grodzinski ldquoHybridization enhancement using cavitationmicrostreamingrdquo Analytical Chemistry vol 75 no 8 pp 1911ndash1917 2003

[4] M KMcQuain K Seale J Peek et al ldquoChaoticmixer improvesmicroarray hybridizationrdquoAnalytical Biochemistry vol 325 no2 pp 215ndash226 2004

[5] Y C Chung Y C Lin M Z Shiu and W N T ChangldquoMicrofluidic chip for fast nucleic acid hybridizationrdquo Lab ona Chip vol 3 no 4 pp 228ndash233 2003

[6] D R Reyes D Iossifidis P A Auroux and A Manz ldquoMicrototal analysis systems 1 Introduction theory and technologyrdquoAnalytical Chemistry vol 74 no 12 pp 2623ndash2636 2002

[7] P-A Auroux D Iossifidis D R Reyes and A Manz ldquoMicrototal analysis systems 2 Analytical standard operations andapplicationsrdquo Analytical Chemistry vol 74 no 12 pp 2637ndash2652 2002

[8] T Vilkner D Janasek and A Manz ldquoMicro total analysissystems Recent developmentsrdquo Analytical Chemistry vol 76no 12 pp 3373ndash3386 2004

[9] Y Zhang and P Ozdemir ldquoMicrofluidic DNA amplificationndasha reviewrdquo Analytica Chimica Acta vol 638 no 2 pp 115ndash1252009

[10] A Bange H B Halsall and W R Heineman ldquoMicrofluidicimmunosensor systemsrdquo Biosensors and Bioelectronics vol 20no 12 pp 2488ndash2503 2005

[11] K F Lei ldquoMicrofluidic systems for diagnostic applications areviewrdquo Journal of Laboratory Automation vol 17 pp 330ndash3472012

[12] Y Xia and G M Whitesides ldquoSoft lithographyrdquo Annual Reviewof Materials Science vol 28 no 1 pp 153ndash184 1998

[13] A Gerlach G Knebel A E Guber et al ldquoMicrofabricationof single-use plastic microfluidic devices for high-throughputscreening and DNA analysisrdquo Microsystem Technologies vol 7no 5-6 pp 265ndash268 2002


[14] W W Y Chow K F Lei G Shi W J Li and Q HuangldquoMicrofluidic channel fabrication by PDMS-interface bondingrdquoSmart Materials and Structures vol 15 pp S112ndashS116 2006

[15] K F Lei S AhsanN BudraaW J Li and J DMai ldquoMicrowavebonding of polymer-based substrates for potential encapsulatedmicronanofluidic device fabricationrdquo Sensors and Actuators APhysical vol 114 no 2-3 pp 340ndash346 2004

[16] Z J Jia Q Fang and Z-L Fang ldquoBonding of glass microfluidicchips at room temperaturesrdquo Analytical Chemistry vol 76 no18 pp 5597ndash5602 2004

[17] CW Tsao andD LDeVoe ldquoBonding of thermoplastic polymermicrofluidicsrdquo Microfluidics and Nanofluidics vol 6 no 1 pp1ndash16 2009

[18] K F Lei H Cheng K Y Choy and L M C Chow ldquoElec-trokinetic DNA concentration in microsystemsrdquo Sensors andActuators A Physical vol 156 no 2 pp 381ndash387 2009

[19] Y He M Tsutsui C Fan M Taniguchi and T Kawai ldquoGatemanipulation of DNA capture into nanoporesrdquo ACS Nano vol5 no 10 pp 8391ndash8397 2011

[20] M A Burns B N Johnson S N Brahmasandra et al ldquoAnintegrated nanoliter DNA analysis devicerdquo Science vol 282 no5388 pp 484ndash487 1998

[21] F Wang and M A Burns ldquoPerformance of nanoliter-sizeddroplet-based microfluidic PCRrdquo Biomedical Microdevices vol11 no 5 pp 1071ndash1080 2009

[22] L Shui J G Bomer M Jin E T Carlen and A van denBerg ldquoMicrofluidic DNA fragmentation for on-chip genomicanalysisrdquo Nanotechnology vol 22 no 49 Article ID 4940132011

[23] J Khandurina T E McKnight S C Jacobson L C WatersR S Foote and J M Ramsey ldquoIntegrated system for rapidPCR-based DNA analysis in microfluidic devicesrdquo AnalyticalChemistry vol 72 no 13 pp 2995ndash3000 2000

[24] D Sabourin J Petersen D Snakenborg et al ldquoMicrofluidicDNA microarrays in PMMA chips streamlined fabrication viasimultaneous DNA immobilization and bonding activation bybrief UV exposurerdquo Biomedical Microdevices vol 12 no 4 pp673ndash681 2010

[25] A H Diercks A Ozinsky C L Hansen J M Spotts D JRodriguez and A Aderem ldquoA microfluidic device for mul-tiplexed protein detection in nano-liter volumesrdquo AnalyticalBiochemistry vol 386 no 1 pp 30ndash35 2009

[26] K F Lei ldquoQuantitative electrical detection of immobilizedprotein using gold nanoparticles and gold enhancement on abiochiprdquo Measurement Science and Technology vol 22 no 10Article ID 105802 2011

[27] K F Lei and Y K C Butt ldquoColorimetric immunoassay chipbased on gold nanoparticles and gold enhancementrdquoMicroflu-idics and Nanofluidics vol 8 no 1 pp 131ndash137 2010

[28] A E Herr A V Hatch D J Throckmorton et al ldquoMicrofluidicimmunoassays as rapid saliva-based clinical diagnosticsrdquo Pro-ceedings of the National Academy of Sciences of the United Statesof America vol 104 no 13 pp 5268ndash5273 2007

[29] A Bhattacharyya and C M Klapperich ldquoDesign and testingof a disposable microfluidic chemiluminescent immunoassayfor disease biomarkers in human serum samplesrdquo BiomedicalMicrodevices vol 9 no 2 pp 245ndash251 2007

[30] S Lai S Wang J Luo L J Lee S T Yang and M J MadouldquoDesign of a compact disk-like microfluidic platform forenzyme-linked immunosorbent assayrdquo Analytical Chemistryvol 76 no 7 pp 1832ndash1837 2004

[31] D Yang X Niu Y Liu et al ldquoElectrospun nanofibrous mem-branes a novel solid substrate for microfluidic immunoassaysfor HIVrdquo Advanced Materials vol 20 no 24 pp 4770ndash47752008

[32] T Glawdel and C L Ren ldquoElectro-osmotic flow control forliving cell analysis in microfluidic PDMS chipsrdquo MechanicsResearch Communications vol 36 no 1 pp 75ndash81 2009

[33] F T G van den Brink E Gool J-P Frimat J Bomer A van denBerg and S le Gac ldquoParallel single-cell analysis microfluidicplatformrdquo Electrophoresis vol 32 no 22 pp 3094ndash3100 2011

[34] R N Zare and S Kim ldquoMicrofluidic platforms for single-cellanalysisrdquo Annual Review of Biomedical Engineering vol 12 pp187ndash201 2010

[35] G Mehta J Lee W Cha Y-C Tung J J Linderman and STakayama ldquoHard top soft bottom microfluidic devices for cellculture and chemical analysisrdquoAnalytical Chemistry vol 81 no10 pp 3714ndash3722 2009

[36] K F Lei and P H M Leung ldquoMicroelectrode array biosensorfor the detection of Legionella pneumophilardquo MicroelectronicEngineering vol 91 pp 174ndash177 2012

[37] K F Lei M H Wu C W Hsu and Y D Chen ldquoReal-timeand non-invasive impedimetric monitoring of cell proliferationand chemosensitivity in a perfusion 3D cell culturemicrofluidicchiprdquo Biosensors and Bioelectronics vol 51 pp 16ndash21 2014

[38] K F LeiMHWu P Y Liao YMChen andTM Pan ldquoDevel-opment of a micro-scale perfusion 3D cell culture biochip withan incorporated electrical impedance measurement scheme forthe quantification of cell number in a 3D cell culture constructrdquoMicrofluidics and Nanofluidics vol 12 no 1ndash4 pp 117ndash125 2012

[39] M Bu T Melvin G Ensell J S Wilkinson and A G R EvansldquoDesign and theoretical evaluation of a novel microfluidicdevice to be used for PCRrdquo Journal of Micromechanics andMicroengineering vol 13 pp S125ndashS130 2003

[40] K-S Ma H Zhou J Zoval and M Madou ldquoDNA hybridiza-tion detection by label free versus impedance amplifying labelwith impedance spectroscopyrdquo Sensors and Actuators B Chem-ical vol 114 no 1 pp 58ndash64 2006

[41] S J Park T A Taton and C A Mirkin ldquoArray-based electricaldetection of DNA with nanoparticle probesrdquo Science vol 295no 5559 pp 1503ndash1506 2002

[42] C Fang Y Fan J Kong Z Gao and N BalasubramanianldquoElectrical detection of oligonucleotide using an aggregate ofgold nanoparticles as a conductive tagrdquo Analytical Chemistryvol 80 no 24 pp 9387ndash9394 2008

[43] R L Testerman N R Hagfors and S I Schwartz ldquoDesign andevaluation of nerve stimulating electrodesrdquo Medical researchengineering vol 10 no 1 pp 6ndash11 1971

[44] M Sawan F Mounaim and G Lesbros ldquoWireless monitoringof electrode-tissues interfaces for long term characterizationrdquoAnalog Integrated Circuits and Signal Processing vol 55 no 1pp 103ndash114 2008

[45] A Yufera G Leger E O Rodriguez-Villegas et al ldquoAn inte-grated circuit for tissue impedance measurerdquo in Proceedings ofthe 2nd Annual International IEEE-EMB Special Topic Confer-ence on Microtechnologies in Medicine amp Biology pp 88ndash93Madison Wis USA 2002

[46] A Yufera A Rueda JMMunoz RDoldan G Leger and EORodrıguez-Villegas ldquoA tissue impedance measurement chip formyocardial ischemia detectionrdquo IEEE Transactions on Circuitsand Systems I Regular Papers vol 52 no 12 pp 2620ndash26282005


[47] R Pallas-Areny and J GWebster ldquoBioelectric impedance mea-surements using synchronous samplingrdquo IEEE Transactions onBiomedical Engineering vol 40 no 8 pp 824ndash829 1993

[48] J Sacristan-Riquelme F Segura-Quijano A Baldi and MTeresa Oses ldquoLow power impedance measurement integratedcircuit for sensor applicationsrdquoMicroelectronics Journal vol 40no 1 pp 177ndash184 2009

[49] A Yufera and A Rueda ldquoDesign of a CMOS closed-loopsystem with applications to bio-impedance measurementsrdquoMicroelectronics Journal vol 41 no 4 pp 231ndash239 2010

[50] A S Sedra and K C Smith Microelectronic Circuit OxfordUniversity Press New York NY USA 5th edition 2007

[51] A Harb and M Sawan ldquoNew low-power low-voltage high-CMRR CMOS instrumentation amplifierrdquo in Proceedings of theIEEE International Symposium on Circuits and Systems (ISCASrsquo99) vol 6 pp 97ndash100 June 1999

[52] C C Enz and G C Temes ldquoCircuit techniques for reducingthe effects of Op-Amp imperfections autozeroing correlateddouble sampling and chopper stabilizationrdquo Proceedings of theIEEE vol 84 no 11 pp 1584ndash1614 1996

[53] R R Harrison and C Charles ldquoA low-power low-noise CMOSamplifier for neural recording applicationsrdquo IEEE Journal ofSolid-State Circuits vol 38 no 6 pp 958ndash965 2003

[54] J A Tierno A V Rylyakov and D J Friedman ldquoA wide powersupply range wide tuning range all static cmos all digital pllin 65 nm SOIrdquo IEEE Journal of Solid-State Circuits vol 43 pp42ndash51 2008

[55] C S Alex Gong K W Yao and M T Shiue ldquoA CMOS multi-channel electrical stimulation prototype systemrdquo InternationalJournal of CircuitTheory andApplications vol 41 no 3 pp 238ndash258 2013

[56] M Ghovanloo and K Najafi ldquoA wireless implantable mul-tichannel microstimulating system-on-a-chip with modulararchitecturerdquo IEEE Transactions on Neural Systems and Reha-bilitation Engineering vol 15 no 3 pp 449ndash457 2007

[57] Y Chen C C Wong T S Pui et al ldquoCMOS high densityelectrical impedance biosensor array for tumor cell detectionrdquoSensors and Actuators B Chemical vol 173 pp 903ndash907 2012

[58] G Lesbros and M Sawan ldquoMultiparameters monitoring forlong term in-vivo characterization of electrode-tissues con-tactsrdquo in Proceedings of the 13th IEEE International Conferenceon Electronics Circuits and Systems (ICECS rsquo06) pp 25ndash28Nice France December 2006

[59] C S A Gong K W Yao M T Shiue and Y ChangldquoAn impedance measurement analog front end for wirelesslybioimplantable applicationsrdquo in Proceedings of the IEEE AsiaPacific Conference on Circuits and Systems (APCCAS rsquo12) pp172ndash175 Kaohsiung Taiwan December 2012

[60] I Bantounas L A Phylactou and J B Uney ldquoRNA interferenceand the use of small interfering RNA to study gene function inmammalian systemsrdquo Journal of Molecular Endocrinology vol33 no 3 pp 545ndash557 2004

[61] Y A Abassi B Xi W Zhang et al ldquoKinetic cell-based morpho-logical screening prediction ofmechanismof compound actionand off-target effectsrdquo Chemistry and Biology vol 16 no 7 pp712ndash723 2009

[62] ldquoUsing the xCELLigence System for Functional GenomicsAssessing Gene Function in Real Timerdquo Application Note ofACEA Biosciences Inc

Submit your manuscripts athttpwwwhindawicom

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014


MEDIATORSINFLAMMATION

of


Behavioural Neurology

EndocrinologyInternational Journal of



Disease Markers


BioMed Research International

OncologyJournal of



Oxidative Medicine and Cellular Longevity


PPAR Research

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Immunology ResearchHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

ObesityJournal of



Computational and Mathematical Methods in Medicine

OphthalmologyJournal of


Diabetes ResearchJournal of



Research and TreatmentAIDS


Gastroenterology Research and Practice


Parkinsonrsquos Disease

Evidence-Based Complementary and Alternative Medicine

Volume 2014Hindawi Publishing Corporationhttpwwwhindawicom


based on the collision possibility Because of the reductionin diffusion distance and increase in surface-to-volume ratioin microfluidic environment the reaction kinetics of DNAstrands binding reaction was shown significantly acceleratedcompared with the conventional microplate technique [1ndash5] That results in greatly improving the response time ofthe biological reaction and the sensitivity of the biologicaldetectionMicrofluidic system is often interpreted to aminia-turized version of bioanalytical laboratory It can perform theentire analytical protocol such as sample preparation reagentapplication biological reaction and detection automaticallyto eliminate the handling fault Since microfluidic system isa miniaturized instrument portability is realizable for thepoint-of-care diagnostic applications

The aim of this paper is to report on recent developmentson miniaturized instruments for genomic applications Anoverview of microfluidic systems and their demonstrationsfor genomic diagnosis will be discussed Moreover impedi-metric detection is found to be a promising technique forpoint-of-care genomic detection because the impedimetricsignal can easily be analyzed by miniaturized electricalcircuits In-depth discussion of the consideration and reviewof impedimetric circuits and systems will also be included inthis article

2 Miniaturized InstrumentsMicrofluidic Systems

In the past decade development of the microfluidic tech-nology becomes intensive and many research articles areavailable [6ndash11] The fabrication of microfluidic systemswas originally based on the silicon fabrication technologyfrom semiconductor and microelectromechanical systems(MEMS) Silicon microfabrication is well established butsilicon material is not optically transparent and is electricallyconductive Hence it is not appropriate for the biomedicalapplications For example the microfluidic system for cellculture is required to be transparent for continuous opti-cal monitoring of cell morphology Moreover microfluidicsystem for glucose detection is based on electrochemicalreaction which needs insulated substrate for measurementTherefore silicon may not be an appropriate material whenoptical and electrochemical detections are adopted in themicrofluidic systems Therefore glass and polymeric mate-rials were used because they are less expensive opticallytransparent and not electrically conductive Specific fab-rication technologies for microfluidic systems were intro-duced such as soft lithography hot embossing and substratebonding techniques Soft lithography represents a nonpho-tolithographic strategy based on self-assembly and replicamolding for carrying out micro- and nanofabrication [12]An elastomeric stamp with patterned relief structures onits surface is used to generate patterns and structures withfeature sizes ranging from 30 nm to 100 120583m It provides aconvenient effective and low-cost method for the forma-tion and manufacturing of micro- and nanostructures Hotembossing technique is for mass production of plastic micro-components [13] A mold with microstructures is pressed

into a thermoplastic polymer film heated beyond its glasstransition temperature under vacuum After cooling downthe microstructures can be transferred from the mold to thepolymer film To fabricate a functional microfluidic systemsubstrate bonding is an important process and adhesionbetween substrates is a problem of great practical concernThermal compression ultrasonic or gluing by application ofeither epoxy or methanol may induce global and localizedgeometric deformation of the substrates or leave an interfaciallayer with significant thickness variation Therefore specialbonding processes for glass and polymeric materials havebeen developed for fabricating microfluidic systems [14ndash17] Localized welding of polymeric materials embeddedmetal films located between the desired bond surfaces bymicrowave energy has been developed [15] The bonding canbe achieved with 10Wmicrowave power in 120 s

Based on the mature development of the fabricationtechnology a board spectrum of biological analytical appli-cations has been demonstrated using microfluidic systemssuch as DNA analysis [1 18ndash24] immunoassay [25ndash31]and cell analysis [32ndash38] For example immunoassay oncompact disc (CD) has been demonstrated and fluids inCD were manipulated by the centrifugal forces controlledby the rotational speed of the CD [30] Illustration andphotograph of the CD-based microfluidic system are shownin Figure 1 High throughput screening of analytes couldbe realized by simultaneous functions in parallel layoutson the CD Enzyme-linked immunosorbent assay (ELISA)was demonstrated on this CD-based platform Anotherexample is to construct a microfluidic chip for real-time andnoninvasive impedimetric monitoring of cell proliferationand chemosensitivity in three-dimensional (3D) cell cultureconstruct as shown in Figure 2 [37] Human oral cancercells (OEC-M1) were encapsulated in 3D agarose scaffoldand cultured in a miniaturized chamber under perfusionof tested substance This setting provides a more in vitrophysiologically relevant microenvironment to better mimicthe complex in vivo microenvironment These excellentdevelopments showed the capability of microfluidic systemfor performing complex analytical applications Commercialpossibility is obvious because the microfluidic system canprovide a total solution of biological analysis from the sampleapplication to the display of the analysis results Point-of-care diagnostic applications can be realized based on theadvantages ofminiaturization integration and automation ofthe microfluidic system

3 Integrated Microfluidic Genomic Systems

Microfluidic systems have been also applied to the genomicapplications System integrated with microchannels heaterstemperature sensors and fluorescence detectors was fabri-cated for the functions of capturing DNA mixing solutionsamplifyingDNA and separating and detecting of those prod-ucts [20] These complicated operations could be performedon a single glass and silicon substrate Strand displacementamplification experiment was conducted and showed that thespecific target DNA was successfully amplified and detected


(a)

1

2

3

4

5

6

7

8

9

10

11

(b)

7mm

(c)


Fluidic layer


Electrode layer

Perfusion path

3D culturechamber


(a) (b)


Fresh medium


Impedance analyzer

Spent medium

(c)





ZOutlet hole

Inlet hole

Pyrex wafer

Section line

Silicon wafer

Heat sink


pn-diode

Pt heaters


Reactionchambers

90∘C

72∘C

55∘CX

Optical fiber

Pyrex

Silicon

PZT disc

PZT disc

Connection channel


Y

Connection channel




Z998400

Wirebonding

hole

Etched pumpmembrane

ermalisolation

recess

Y998400

Figure 5(a)












(a)

8mm

30mm

120120583m

5mm


R = 2mm

1

2

3

4

(b)



IS(t)

IS(t)

t t

(+)

(minus)

(+)

(minus)

SUTVS(t)










119908





R0

Rct

Ld

Zw

Cd

(a)

Mass transport


Double-layer

mHzf

Ro + Rct

ReZkHz HzRo

minusImZ

(b)







VCO

Demodulator

Demodulator

ADC

ADC

Ze1Ze2

Ze3Ze4

SUT IA

Re

Im90∘

0∘

+

minus





ΔV


Vout+

minus

R4

R4

R3

R3

R2

R2

R1

VNVB

VA VMA1

A2

IR1 A3

+

minus

+

minus

(a)

CM1

CM2

RG

VoutR1

VY

VX

VG

VB

VA

IR1

A1+

minus

A2+

minus

+

minusA3ΔV

I2

I1


I1 minus I2

(b)



119881out = minus1198774

1198773

(1 +21198772

1198771

) (119881119860minus 119881119861) = 1198701(119881119860minus 119881119861) (1)


1198773(or 1198772and 119877




forcing 119881119860= 119881119883and 119881


1




119881out =2119877119866

1198771

(119881119860minus 119881119861) = 1198702(119881119860minus 119881119861) (2)












119871 Owing to





Vo

Vi

CS

120601

120601

120601

++

minus

minusminus

VOS

(a)

C2

C2

R2

R2

C1

C1

Vout

Vin CL

Vip

+

minus

(b)

VbVa

0

R

1GΩ

1MΩ

Vba

(c)







intVref

Vref

LPF

Digital control

sgn[cos(120596t)]sgn[cos(120596t + 1205872)]

1

1

2

3

minus1

HPFOTABuf

OTABias

DAC

cos(120596t)

cos(120596t + 120587)

sim

sim


A

B

C

D

ZMA

ZMC ZMD

ZMB

ZEA

ZEB

ZEC

ZED


+

minus

+

minus


+

minus

+

minus

Vo

Vod

Vxd

V120601

EXOR

IA

AC

DCEA

OTA

120572ia

Rectifier

120572dc int

+

minusint

+

minus

VS120572ea

Vm

Zx

K

Gm

gm

Vx

e1

e2

ix

Vdc

Vref

Current oscillator






119898) can be


119878can be given









Counter electrode

Trapped

CTC cells

Gold microelectrode



(a) (b)

(c)

(d)


ElectrolyteCell





acquisition












Acknowledgments


References






































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















(a)

1

2

3

4

5

6

7

8

9

10

11

(b)

7mm

(c)


Fluidic layer


Electrode layer

Perfusion path

3D culturechamber


(a) (b)


Fresh medium


Impedance analyzer

Spent medium

(c)





ZOutlet hole

Inlet hole

Pyrex wafer

Section line

Silicon wafer

Heat sink


pn-diode

Pt heaters


Reactionchambers

90∘C

72∘C

55∘CX

Optical fiber

Pyrex

Silicon

PZT disc

PZT disc

Connection channel


Y

Connection channel




Z998400

Wirebonding

hole

Etched pumpmembrane

ermalisolation

recess

Y998400

Figure 5(a)












(a)

8mm

30mm

120120583m

5mm


R = 2mm

1

2

3

4

(b)



IS(t)

IS(t)

t t

(+)

(minus)

(+)

(minus)

SUTVS(t)










119908





R0

Rct

Ld

Zw

Cd

(a)

Mass transport


Double-layer

mHzf

Ro + Rct

ReZkHz HzRo

minusImZ

(b)







VCO

Demodulator

Demodulator

ADC

ADC

Ze1Ze2

Ze3Ze4

SUT IA

Re

Im90∘

0∘

+

minus





ΔV


Vout+

minus

R4

R4

R3

R3

R2

R2

R1

VNVB

VA VMA1

A2

IR1 A3

+

minus

+

minus

(a)

CM1

CM2

RG

VoutR1

VY

VX

VG

VB

VA

IR1

A1+

minus

A2+

minus

+

minusA3ΔV

I2

I1


I1 minus I2

(b)



119881out = minus1198774

1198773

(1 +21198772

1198771

) (119881119860minus 119881119861) = 1198701(119881119860minus 119881119861) (1)


1198773(or 1198772and 119877




forcing 119881119860= 119881119883and 119881


1




119881out =2119877119866

1198771

(119881119860minus 119881119861) = 1198702(119881119860minus 119881119861) (2)












119871 Owing to





Vo

Vi

CS

120601

120601

120601

++

minus

minusminus

VOS

(a)

C2

C2

R2

R2

C1

C1

Vout

Vin CL

Vip

+

minus

(b)

VbVa

0

R

1GΩ

1MΩ

Vba

(c)







intVref

Vref

LPF

Digital control

sgn[cos(120596t)]sgn[cos(120596t + 1205872)]

1

1

2

3

minus1

HPFOTABuf

OTABias

DAC

cos(120596t)

cos(120596t + 120587)

sim

sim


A

B

C

D

ZMA

ZMC ZMD

ZMB

ZEA

ZEB

ZEC

ZED


+

minus

+

minus


+

minus

+

minus

Vo

Vod

Vxd

V120601

EXOR

IA

AC

DCEA

OTA

120572ia

Rectifier

120572dc int

+

minusint

+

minus

VS120572ea

Vm

Zx

K

Gm

gm

Vx

e1

e2

ix

Vdc

Vref

Current oscillator






119898) can be


119878can be given









Counter electrode

Trapped

CTC cells

Gold microelectrode



(a) (b)

(c)

(d)


ElectrolyteCell





acquisition












Acknowledgments


References






































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















ZOutlet hole

Inlet hole

Pyrex wafer

Section line

Silicon wafer

Heat sink


pn-diode

Pt heaters


Reactionchambers

90∘C

72∘C

55∘CX

Optical fiber

Pyrex

Silicon

PZT disc

PZT disc

Connection channel


Y

Connection channel




Z998400

Wirebonding

hole

Etched pumpmembrane

ermalisolation

recess

Y998400

Figure 5(a)












(a)

8mm

30mm

120120583m

5mm


R = 2mm

1

2

3

4

(b)



IS(t)

IS(t)

t t

(+)

(minus)

(+)

(minus)

SUTVS(t)










119908





R0

Rct

Ld

Zw

Cd

(a)

Mass transport


Double-layer

mHzf

Ro + Rct

ReZkHz HzRo

minusImZ

(b)







VCO

Demodulator

Demodulator

ADC

ADC

Ze1Ze2

Ze3Ze4

SUT IA

Re

Im90∘

0∘

+

minus





ΔV


Vout+

minus

R4

R4

R3

R3

R2

R2

R1

VNVB

VA VMA1

A2

IR1 A3

+

minus

+

minus

(a)

CM1

CM2

RG

VoutR1

VY

VX

VG

VB

VA

IR1

A1+

minus

A2+

minus

+

minusA3ΔV

I2

I1


I1 minus I2

(b)



119881out = minus1198774

1198773

(1 +21198772

1198771

) (119881119860minus 119881119861) = 1198701(119881119860minus 119881119861) (1)


1198773(or 1198772and 119877




forcing 119881119860= 119881119883and 119881


1




119881out =2119877119866

1198771

(119881119860minus 119881119861) = 1198702(119881119860minus 119881119861) (2)












119871 Owing to





Vo

Vi

CS

120601

120601

120601

++

minus

minusminus

VOS

(a)

C2

C2

R2

R2

C1

C1

Vout

Vin CL

Vip

+

minus

(b)

VbVa

0

R

1GΩ

1MΩ

Vba

(c)







intVref

Vref

LPF

Digital control

sgn[cos(120596t)]sgn[cos(120596t + 1205872)]

1

1

2

3

minus1

HPFOTABuf

OTABias

DAC

cos(120596t)

cos(120596t + 120587)

sim

sim


A

B

C

D

ZMA

ZMC ZMD

ZMB

ZEA

ZEB

ZEC

ZED


+

minus

+

minus


+

minus

+

minus

Vo

Vod

Vxd

V120601

EXOR

IA

AC

DCEA

OTA

120572ia

Rectifier

120572dc int

+

minusint

+

minus

VS120572ea

Vm

Zx

K

Gm

gm

Vx

e1

e2

ix

Vdc

Vref

Current oscillator






119898) can be


119878can be given









Counter electrode

Trapped

CTC cells

Gold microelectrode



(a) (b)

(c)

(d)


ElectrolyteCell





acquisition












Acknowledgments


References






































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of



















(a)

8mm

30mm

120120583m

5mm


R = 2mm

1

2

3

4

(b)



IS(t)

IS(t)

t t

(+)

(minus)

(+)

(minus)

SUTVS(t)










119908





R0

Rct

Ld

Zw

Cd

(a)

Mass transport


Double-layer

mHzf

Ro + Rct

ReZkHz HzRo

minusImZ

(b)







VCO

Demodulator

Demodulator

ADC

ADC

Ze1Ze2

Ze3Ze4

SUT IA

Re

Im90∘

0∘

+

minus





ΔV


Vout+

minus

R4

R4

R3

R3

R2

R2

R1

VNVB

VA VMA1

A2

IR1 A3

+

minus

+

minus

(a)

CM1

CM2

RG

VoutR1

VY

VX

VG

VB

VA

IR1

A1+

minus

A2+

minus

+

minusA3ΔV

I2

I1


I1 minus I2

(b)



119881out = minus1198774

1198773

(1 +21198772

1198771

) (119881119860minus 119881119861) = 1198701(119881119860minus 119881119861) (1)


1198773(or 1198772and 119877




forcing 119881119860= 119881119883and 119881


1




119881out =2119877119866

1198771

(119881119860minus 119881119861) = 1198702(119881119860minus 119881119861) (2)












119871 Owing to





Vo

Vi

CS

120601

120601

120601

++

minus

minusminus

VOS

(a)

C2

C2

R2

R2

C1

C1

Vout

Vin CL

Vip

+

minus

(b)

VbVa

0

R

1GΩ

1MΩ

Vba

(c)







intVref

Vref

LPF

Digital control

sgn[cos(120596t)]sgn[cos(120596t + 1205872)]

1

1

2

3

minus1

HPFOTABuf

OTABias

DAC

cos(120596t)

cos(120596t + 120587)

sim

sim


A

B

C

D

ZMA

ZMC ZMD

ZMB

ZEA

ZEB

ZEC

ZED


+

minus

+

minus


+

minus

+

minus

Vo

Vod

Vxd

V120601

EXOR

IA

AC

DCEA

OTA

120572ia

Rectifier

120572dc int

+

minusint

+

minus

VS120572ea

Vm

Zx

K

Gm

gm

Vx

e1

e2

ix

Vdc

Vref

Current oscillator






119898) can be


119878can be given









Counter electrode

Trapped

CTC cells

Gold microelectrode



(a) (b)

(c)

(d)


ElectrolyteCell





acquisition












Acknowledgments


References






































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















R0

Rct

Ld

Zw

Cd

(a)

Mass transport


Double-layer

mHzf

Ro + Rct

ReZkHz HzRo

minusImZ

(b)







VCO

Demodulator

Demodulator

ADC

ADC

Ze1Ze2

Ze3Ze4

SUT IA

Re

Im90∘

0∘

+

minus





ΔV


Vout+

minus

R4

R4

R3

R3

R2

R2

R1

VNVB

VA VMA1

A2

IR1 A3

+

minus

+

minus

(a)

CM1

CM2

RG

VoutR1

VY

VX

VG

VB

VA

IR1

A1+

minus

A2+

minus

+

minusA3ΔV

I2

I1


I1 minus I2

(b)



119881out = minus1198774

1198773

(1 +21198772

1198771

) (119881119860minus 119881119861) = 1198701(119881119860minus 119881119861) (1)


1198773(or 1198772and 119877




forcing 119881119860= 119881119883and 119881


1




119881out =2119877119866

1198771

(119881119860minus 119881119861) = 1198702(119881119860minus 119881119861) (2)












119871 Owing to





Vo

Vi

CS

120601

120601

120601

++

minus

minusminus

VOS

(a)

C2

C2

R2

R2

C1

C1

Vout

Vin CL

Vip

+

minus

(b)

VbVa

0

R

1GΩ

1MΩ

Vba

(c)







intVref

Vref

LPF

Digital control

sgn[cos(120596t)]sgn[cos(120596t + 1205872)]

1

1

2

3

minus1

HPFOTABuf

OTABias

DAC

cos(120596t)

cos(120596t + 120587)

sim

sim


A

B

C

D

ZMA

ZMC ZMD

ZMB

ZEA

ZEB

ZEC

ZED


+

minus

+

minus


+

minus

+

minus

Vo

Vod

Vxd

V120601

EXOR

IA

AC

DCEA

OTA

120572ia

Rectifier

120572dc int

+

minusint

+

minus

VS120572ea

Vm

Zx

K

Gm

gm

Vx

e1

e2

ix

Vdc

Vref

Current oscillator






119898) can be


119878can be given









Counter electrode

Trapped

CTC cells

Gold microelectrode



(a) (b)

(c)

(d)


ElectrolyteCell





acquisition












Acknowledgments


References






































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















ΔV


Vout+

minus

R4

R4

R3

R3

R2

R2

R1

VNVB

VA VMA1

A2

IR1 A3

+

minus

+

minus

(a)

CM1

CM2

RG

VoutR1

VY

VX

VG

VB

VA

IR1

A1+

minus

A2+

minus

+

minusA3ΔV

I2

I1


I1 minus I2

(b)



119881out = minus1198774

1198773

(1 +21198772

1198771

) (119881119860minus 119881119861) = 1198701(119881119860minus 119881119861) (1)


1198773(or 1198772and 119877




forcing 119881119860= 119881119883and 119881


1




119881out =2119877119866

1198771

(119881119860minus 119881119861) = 1198702(119881119860minus 119881119861) (2)












119871 Owing to





Vo

Vi

CS

120601

120601

120601

++

minus

minusminus

VOS

(a)

C2

C2

R2

R2

C1

C1

Vout

Vin CL

Vip

+

minus

(b)

VbVa

0

R

1GΩ

1MΩ

Vba

(c)







intVref

Vref

LPF

Digital control

sgn[cos(120596t)]sgn[cos(120596t + 1205872)]

1

1

2

3

minus1

HPFOTABuf

OTABias

DAC

cos(120596t)

cos(120596t + 120587)

sim

sim


A

B

C

D

ZMA

ZMC ZMD

ZMB

ZEA

ZEB

ZEC

ZED


+

minus

+

minus


+

minus

+

minus

Vo

Vod

Vxd

V120601

EXOR

IA

AC

DCEA

OTA

120572ia

Rectifier

120572dc int

+

minusint

+

minus

VS120572ea

Vm

Zx

K

Gm

gm

Vx

e1

e2

ix

Vdc

Vref

Current oscillator






119898) can be


119878can be given









Counter electrode

Trapped

CTC cells

Gold microelectrode



(a) (b)

(c)

(d)


ElectrolyteCell





acquisition












Acknowledgments


References






































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















Vo

Vi

CS

120601

120601

120601

++

minus

minusminus

VOS

(a)

C2

C2

R2

R2

C1

C1

Vout

Vin CL

Vip

+

minus

(b)

VbVa

0

R

1GΩ

1MΩ

Vba

(c)







intVref

Vref

LPF

Digital control

sgn[cos(120596t)]sgn[cos(120596t + 1205872)]

1

1

2

3

minus1

HPFOTABuf

OTABias

DAC

cos(120596t)

cos(120596t + 120587)

sim

sim


A

B

C

D

ZMA

ZMC ZMD

ZMB

ZEA

ZEB

ZEC

ZED


+

minus

+

minus


+

minus

+

minus

Vo

Vod

Vxd

V120601

EXOR

IA

AC

DCEA

OTA

120572ia

Rectifier

120572dc int

+

minusint

+

minus

VS120572ea

Vm

Zx

K

Gm

gm

Vx

e1

e2

ix

Vdc

Vref

Current oscillator






119898) can be


119878can be given









Counter electrode

Trapped

CTC cells

Gold microelectrode



(a) (b)

(c)

(d)


ElectrolyteCell





acquisition












Acknowledgments


References






































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















intVref

Vref

LPF

Digital control

sgn[cos(120596t)]sgn[cos(120596t + 1205872)]

1

1

2

3

minus1

HPFOTABuf

OTABias

DAC

cos(120596t)

cos(120596t + 120587)

sim

sim


A

B

C

D

ZMA

ZMC ZMD

ZMB

ZEA

ZEB

ZEC

ZED


+

minus

+

minus


+

minus

+

minus

Vo

Vod

Vxd

V120601

EXOR

IA

AC

DCEA

OTA

120572ia

Rectifier

120572dc int

+

minusint

+

minus

VS120572ea

Vm

Zx

K

Gm

gm

Vx

e1

e2

ix

Vdc

Vref

Current oscillator






119898) can be


119878can be given









Counter electrode

Trapped

CTC cells

Gold microelectrode



(a) (b)

(c)

(d)


ElectrolyteCell





acquisition












Acknowledgments


References






































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















Counter electrode

Trapped

CTC cells

Gold microelectrode



(a) (b)

(c)

(d)


ElectrolyteCell





acquisition












Acknowledgments


References






































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of






















Acknowledgments


References






































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of








































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of
















Review Article Advances in Miniaturized Instruments for ...

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