Post on 01-Jul-2015
description
Centripetal Pumping by Stored Chemical Energy Towards Multi-step Assays on the Centrifugal Platform
What is Microfluidics ?
Microfluidics is a multidisciplinary field intersecting Engineering, Physics, Biotechnology and Nanotechnology.
Over the years centrifugal microfluidic technology has found its way in bio analytical assays in areas such as biomedical diagnostics, Bioprocess monitoring, environmental screening.
Centrifugal Microfluidics uses centrifugal force through spinning of disc shaped cartridges, similar in geometry to a CD or DVD to implement Laboratory Unit Operatoins(LUO’s) such as pumping, metering, mixing, routing.
Advantages The Lab on a Disc , LoaD, is low cost, simple
and robust. Independent of complex instrumentation such
as pumps; interfacing takes place via direct pipetting.
Disadvantages Unidirectional nature of the centrifugal force.
In this project initial work has been done towards using stored chemical energy in the form of low-cost baking powder to pump sample from the periphery of the disc to the centre of the disc and back several times.
This work is then applied towards application in RNA extraction and purification from cell homogenate.
Disc design and assembly. Designing is done on Solidworks, a three
dimensional (3-D) modelling tool used to create accurate representation of objects.
Manufacturing Methods
Schematic of disc design
The discs are made of four layers of poly-methyl methacrylate (PMMA), 1.5mm thick and four layers of pressure sensitive adhesive (PSA), 86μm thick.
Schematic of Disc Manufacture
Small features such as microchannels, which assist in the liquid transport and pneumatic venting, are created from voids cut in PSA using the knife cutter
Pro Robo Cutter
Larger features such as reservoirs, for holding liquid, are cut using the Laser cutter (Epilog Zing, USA)
Laser Cutter, Epilog Zing
As the dissolvable films (DF) are non-adhesive they were attached to the double sided pressure sensitive adhesive (PSA) to create sticky tabs.
Two different grades of DF’s were used throughout this work- KC and Embroidery.
KC film Embroidery Film
All the different layers are assembled on a alignment jig and rolled using a laminating machine
The discs are characterised on an experimental spin stand. Briefly, the discs are spun on a computer controlled spindle motor.
Results
Baking Powder Pump A disc was built to demonstrate successful
pumping and valving principle. The disc was able to pump fluid successfully
inwards and outwards 3 times.
Principle of Baking Powder Pumping
RNA Extraction Disc was designed and manufactured to
pump reagents through a bead filled chamber for RNA extraction.
The different fluids are pumped sequentially through the DF burst valve.
Reagent pumping from different chambers successfully achieved but the order of the valve burst needs further optimisation.
The burst rate can be varied by changing the dimensions of the DF burst valves in the sequential release system.
Sample IPA
Ethanol
Buffer Solution
Ancillary Liquid
0
50,000
100,000
150,000
200,000
250,000
1st 2nd 3rd 4th 5thChambers
Burst Rate
RPM
Sample IPA
Ethanol
Buffer Solution
Ancillary Liquid
0
50,000
100,000
150,000
200,000
250,000
1st 2nd 3rd 4th 5thChambers
Burst Rate
RPM
Sample IPA
Ethanol Buffer Solution
Ancillary Liquid
050,000
100,000150,000200,000250,000
1st 2nd 3rd 4th 5thChambers
RPM
Graph 1 Graph 2
Graph 3
Future Work Successfully achieve the correct burst rate
for pumping the different reagents. Application of this method to extract t-rna
from biological testing.
Thanks for Listening