Design and construction of a micro-milled fluidic device as part of a DNA biosensor

Rosie Townsend

Nick Harris

David Wenn

David Brennan

Introduction

Function and operation of sensor Features of fluidic header (isolation of samples) Fabrication and assembly of header Fluidic design for priming and isolation of samples.

Binding of genetic materialFunction and principle of operation of biosensor

Immobilisation

Hybridisation

Surface stresses

Cantilever deflection

Lechuga et al. (2006) Sensors and Actuators B: Chemical

Microelectronics Institute of Barcelona(IMB-CNM, CSIC)

Optical detection

Cantilever bending detected optically Laser source

VCSEL (vertical cavity surface emission lasers)

Function and principle of operation of biosensor

Lechuga et al. (2006) Sensors and Actuators B: Chemical

Role of Fluidic Header

Isolation of samples Disposable Easily primed Good optical path Incorporate multiple inlets Rapid fabrication

Purpose of header

Deliver reagent(s) to chip

Deliver sample(s)to chip

Fluidic Header

Header assembly

Flow channels milled into acrylic (PMMA) Fabricated using a Datron micro-mill PMMA thermal bonding PDMS gasket Assembled and secured with screws Forms disposable part of header Channels down to 100μm x100μm

Fabrication and assembly

Manifold assembly

Manifold forms permanent part of instrument

Gauge #19 steel tubing Header press fits onto

manifold Gasket seals around tubes

Header

Manifold

Fabrication and assembly

Fluid channels

Common path over chip Multiple discrete paths over chip

Fluidic design

Isolation of samples

Common path – no isolation over chip Multiple path – separate channels feed each cantilever.

Isolate delivery of 20 different nucleic acids, or Isolate delivery of 20 different samples

UV adhesive forms barrier between each channel and cantilever pair.

Fluidic design

(Gasket sealing underside)

Chip

AcrylicAdhesive

PrimingFluidic design

Bubbles trapped in inlet channels

Chip

Acrylic header

PDMS gasket

Acrylic base

Priming valveFluidic design

No flow or operational flow rate

High priming flow rate

Priming valveFluidic design

No pressure and no flow High pressure and flow rate(~0.1ml/s)

Region of valve which is simulated

Priming channel

Priming valveFluidic design

Priming Valve

0

0.2

0.4

0.6

0.8

1

1.2

0.01 0.1 1

Total flow rate (ml/s)

Pro

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f fl

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Normal operation outletPriming outlet

Fluidic design

Conclusions

Design of headers integrated into sensor instrument combining chemical and optical sensing techniques.

Micro-mill fabrication. Fluidic design to manage multiple samples and deliver to

sensor array on single chip. Improve priming and maintain isolation of samples using

a flow actuated PDMS valve

Acknowledgements

Southampton UniversityDave Wenn, Nick Harris, Dave Brennan, Neil Grabham

EU Contract IST-2001-37239