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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n o
f fl
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ts
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