Final Mems Nems (2)

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OUTLINE

NEMS SCHOOL OF BASIC SCIENCEIIT PATNA

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Introduction

Cantilever Technique

Nanocalorimeter


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INTRODUCTION


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Nano-Electro-Mechanical system (NEMS) is the integration of

mechanical elements, sensors, actuators and electronics on

a common silicon substrate.

The Nano mechanical components are fabricated using

compatible micromachining process.

NEMS is the enabling technology allowing the development of

smart products.


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Transducer

a device that converts a primary form of energy into a

corresponding signal with a different energy form

Primary Energy Forms: mechanical, thermal, electromagnetic, optical,

chemical, etc.

take form of a sensor or an actuator

Sensor

a device that detects/measures a signal or stimulus

acquires information from the real world

Actuator

a device that generates a signal or stimulus


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BENEFITS OF NANO MACHINES

Nano-Mechanical devices promise to revolutionize

measurements of extremely small displacements and forces.

Can built with the masses approaching a few attograms(10-18 gm)

and with the cross section of10nm.

A second important attribute Nano machines is that they

dissipate less energy.


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NEMS have an important impact on

1 Medicine and BioengineeringDNA and genetic code analysis and synthesis, drug delivery, diagnosticsand imaging.

2 Avionics and Aerospace

Nano- and microscale actuators and sensors, smart reconfigurablegeometry wings and blades. Navigational gyroscopes

3 In CommunicationDomain

Low insertion loss switches (High Frequency)

Mass Storage Devices; Nano nozzles


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The key elements in the detection of a mass are thevibrational frequency and the deflection of thecantilever

Deflection

Proportional to mass content

Resonance frequency

R =(k/m)1/2

K = spring constant

m= mass

Principle of Microcantilevers

Appl. Phys. Lett., Vol. 85, No. 13, 27 September 2004


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Readout Method

There are several methods available to

observe the deflection and resonance

frequency of the microcantilever

Optical method

Piezoresistive method


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Optical

Optical method requires the use of a low power

laser beam

If microcantilever does not deflect, then no

biomolecules have been absorbed

Laser beam hits a specific position on the position

sensitive detector (PSD)

Major weakness-high cost

*Karolyn M. Hansen, Hai-Feng Ji, Guanghua Wu, Ram Datar, Richard Cote, Arunava Majumdar, and Thomas Thundat

(2001) Cantilever-Based Optical Deflection Assay for Discrimination of DNA Single-Nucleotide Mismatches. Analytical

Chemistry 73 (7): 1567-1571


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Piezoresistive

These sensors measure the strain induced

resistance change

When the biomolecules are absorbed by the

material there is a volumetric change in the

sensing material

Volumetric change is measured by resistance

change in cantilever

Advantages-Low cost

*Viral detection using an embedded piezoresistive microcantilever sensor. Sensors and Actuators A: Physical 107 (3), 219-

224


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Cantilever Sensors


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In this receptor only allow specific analyte to get adsorbed

Rest remain out of contact

Since analyte increases the mass so there is shift in resonance frequency

As mass is added to the cantilever shifts the resonance frequency.


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Virus detection using NEMS

We have used a resonating mechanical cantilever to detectimmunospecific binding of viruses, captured from liquid.

Arrays of surface micromachined, antibody-coatedpolycrystalline silicon nanomechanical cantilever beams wereused to detect binding from various concentrations ofbaculoviruses in a buffer solution.

Because of their small mass, the 0.5 mm X 36 mm cantilevershave mass sensitivities on the order of 10-19g/Hz, enabling thedetection of a mass of about 3 X 10-15 gm.


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With these devices, we can detect the mass of single-virus particles boundto the cantilever. Resonant frequency shift resulting from the adsorbed

mass of the virus particles


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*Amit K. Gupta, Pradeep R. Nair, Demir Akin, Michael R. Ladisch, Steve Broyles,

Muhammad A. Alam, and Rashid Bashir (2006) Anomalous resonance in a

nanomechanical biosensor. PNAS 103 (36): 13362-13367


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Nanocalorimetry

# Calorimetry is the science of measuring the heat of chemical reactions

or physical changes. Calorimetry is performed with a calorimeter.

# The device consists of a substrate with an array ofmicromachined

nanocalorimeter sensors.

# Each nanocalorimeter consists of a silicon nitride membrane and a

tungsten heatingelement that also serves as a temperature gauge.

# The nanocalorimeter sensors are very sensitive, with a resolution of10 nJ/K, allowing thermal analysis of small quantities of material.


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# The small mass of the individual nanocalorimeters enablesmeasurements on samples as small as a few hundred

nanograms at heating rates up to 104K/s.

# Each nanocalorimetric sensor consists of a thin-film

thermistor sandwiched between two electrically insulating

ceramic layers that form a membrane supported by thesubstrate


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Layout of the nanocalorimeter cell

Photograph of the parallel nano-scanning calorimeter.

J. Mater. Res., Vol. 25, No. 11, Nov 2010


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The thermistor is fabricated from an electrically conductive

film and serves to both measure temperature and heat the

sample.

Samples to be measured are limited to the thermistor area

of each sensor, and may be deposited on either side of the

membrane.

The membrane design of the sensor thermally insulates the

sample from the surroundings and ensures that the thermal

mass of the sensor, i.e., the addendum, is very small.

A current passed through the heating element heats the sample and the

calorimetric cell The power dissipated in the thermistor is determined

experimentally from the current supplied to the thermistor and thepotential drop between the voltage probes.

The local temperature change is determined from a four-point thermistor

resistance measurement that has been calibrated to temperature


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Measurements are performed in vacuum to eliminate

convection losses and to provide a chemically inert testing

environment.

ceramic membrane consists ofsilicon nitride, selected

because it is a good electrical insulator and because it is made

easily into thin membranes. low thermal effusivity, which

reduces the heat loss into the membrane.

The thermistor is made oftungsten, because of its large

temperature coefficient of resistance and its small resistivity,

both of which are beneficial to measurement sensitivity


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Operating Principle

The power dissipated in the thermistor can be parsed into

stored power and power lost to the surroundings. At constant pressure, the stored power results in a

changeof the enthalpy of the sample and calorimeter

addendum. If we define a control volume (CV) that

comprises the sample and the calorimeter addendum

P is the total power dissipated in the thermistor,

H is the time rate of change of the enthalpy within the CV,

Q is the heat loss through the boundaries of the CV.


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. The rate of change of the enthalpy can be written as

where T is the temperature of the thermistor. Substituting Eq.

(2) into Eq. (1) and rearranging results in

where T is the heating rate of the thermistor. The left side of

Eq.3 can be directly calculated from measured quantities and

is defined as the calorimetric signal from the sensor.

If Q is known or if its contribution to Eq. (3) is negligible (e.g.,in the case of large heating rates), the change in enthalpy with

temperature, dH/dT, can be determined directly from the

calorimetric signal.


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J. Mater. Res., Vol. 25, No. 11, Nov 2010


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To reduce the effect of the calorimeter addendumand/or heat loss on the measurement, it is often

convenient to perform a reference measurement Equation (3) can then be rewritten to define the

differential calorimetric signal as

del represents the difference between a sensor with

a sample and a sensor that is either empty or

contains a reference sample.


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Application of Nanocalorimetry

Studying molecular interactions

It is also used to investigate the kinetics of phase transformations

and reactions.

Nanocalorimetry makes use of thin-film and micromachiningtechnologies to significantly reduce the addendum of the

calorimeter, enabling ultrasensitive calorimetric measurements


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Pros And Cons

Potential Positive Impacts

Reduction of disease.

Job opportunities in new fields.

Low-cost energy.

Cost reductions with improved efficiencies. Improved product and building materials.

Transportation improvements

Potential Negative Impacts

Material toxicity

Non-biodegradable materials.

Unanticipated consequences.

Job losses due to increased manufacturing efficiencies.


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CONCLUSION


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CONCLUSION NEMS are extensively used and now a days they play vital

role in our life.

Further technology development are going to improve their

synthesis and performance.

Many life saving robot are still to come.

R&D work is still on and lots of new ideas are still to beimplemented.


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REFERENCES

MEMS AND NEMS Systems, Devices, and Structures by Sergey

Edward Lyshevski

http://mems.sandia.gov

http://www.memsnet.org/mems/

http://gen.lib.rus.ec/

www.wikipedia.org

http://www.links999.net/robotics/robots/robots_introduction.html

Applied Physics Letters Volume 85, Number 13


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THANK YOU

Thank you

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