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