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 material Function 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 chipMultiple 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 Acrylic Adhesive

Priming Fluidic design Bubbles trapped in inlet channels Chip Acrylic header PDMS gasket Acrylic base

Priming valve Fluidic design No flow or operational flow rate High priming flow rate

Priming valve Fluidic design No pressure and no flowHigh pressure and flow rate(~0.1ml/s) Region of valve which is simulated Priming channel

Priming valve Fluidic design

Priming Valve 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 University Dave Wenn, Nick Harris, Dave Brennan, Neil Grabham EU Contract IST