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UMD ENMA 490 - Multilayer Microfluidics

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Multilayer MicrofluidicsProblem DefinitionProblem ScopeInitial Material ChoicesInitial Material ChoicesProject DevelopmentDevice Design: Stage 1(Initial Microchannel Design Concept)Device Design: Stage 1 (Initial Microchannel Design Concept)Device Design: Stage 2(Modified Microchannel Design)Device Design: Stage 2(Modified Microchannel Design)Device Design: Stage 2(Modified Microchannel Design)Device Design: Stage 2(Modified Microchannel Design)Processing ProblemsStage 2 (Experimental Results: Trial 1)Stage 2 (Experimental Results: Trial 2)Stage 2 (Test Results: Trial 2)Stage 2 (Test Procedure)Stage 2 (Channel Layout)Device Design: Stage 3(Pressure Actuated Valve Test Design)Device Design: Stage 3(Pressure Actuated Valve Test Design)Device Design: Stage 3 (Pressure Actuated Valve Test Design)Device Design: Stage 3(Pressure Actuated Valve Design)Device Design: Stage 3(Pressure Actuated Valve Design)Device Design: Stage 3(Pressure Actuated Valve Design)Stage 3 (Fabrication Results)Alternative Valve DesignsAlternative Valve DesignsFuture WorkSummaryWe learned to work as a team!Multilayer MicrofluidicsSee my notes in boxes like this, or in red wordsin text. - GWRENMA490Fall 2003Brought to you by: S. Beatty, C. Brooks, S. Dean, M. Hanna, D. Janiak, C. Kung, J. Ni, B. Sadowski, A. Samuel, K. ThakerThis crude hardware was a clever idea (Dan’s) that helped a lot – the creative thinking you need to do in such a project, stimulated by recognizing what is difficult to understand.Problem DefinitionMotivation– BioMEMS research is growing rapidly, but restricted to single layer microfluidics– Development of a multilayer microfluidic design would increase flexibility Goal– Design, construct, and test a controllable microfluidic device with at least two fluid levels– Identify appropriate materials, processes, and device geometries deviceinterconnectI am not sure you were ever really sold on (or did not understand) this analogy to microelectronics. Since the words say nothing about it, this foil makes no sense if viewed without narration.Problem ScopeDesign Requirements– Two-level microfluidic network– Active control elementsMaterial Requirements– Ease of patterning and use in microfabrication– Chemically inert– Low Cost / Obtainable– Optically transparent– Specific Elastic modulus (flexible, rigid)Constraints– Assume external fluid control– Neglect biochemical reactions in channels– Keep design feasible for manufacturingInitial Material ChoicesSubstrate Material• Silicon• Relatively inexpensive• Commonly used in microelectronics• Well known properties and processing techniques• Pyrex• Transparent to visible light• Allows visual monitoring of micro channels• More expensive than siliconAt an early stage of research, cost of materials isn’t so important, and particularly not in such a presentation, where cost issues should be projecting to commercial application. In this regard, Si is considered too expensive a material and Si-based processes too expensive for microfluidic applications.Initial Material ChoicesMicrochannel Material• Poly(dimethylsiloxane) or PDMS• Inexpensive• Poor surface adhesion – releasable from mold• Highly flexible • modulus of 2.5 MPa• SU-8• Is a photoresist• High aspect ratios obtainable• Good surface adhesion to silicon and Pyrex• Very rigid – complementary to PDMS • modulus of 4000 MPaThis doesn’t quite make the point that SU-8 is a resist with the unusual property that it makes quite a good material to leave in place, as a fairly rigid insulator with apparently good biocompatibility.Project DevelopmentDefined ProblemDivided into research groups (BioMEMS, Materials, Devices, and Circuits)Developed Stage 1(Initial Microchannel Design Concept)Developed and tested Stage 2(Modified Microchannel Design)Modified design to integrate vertical vias for multilevel fluid flowDeveloped and tested Stage 3(Final Design: Pressure Actuated Valve Design)Developed fluid control device to manipulate fluid flowSummarized manufacturing and experimental results of final designAs I noted in class, the development team should certainly have included the change in research groups in the first part of the semester, when we identified development, experiment, microchannels, and control groups. I did not receive an updated copy of the presentation that included this, even though I was quite specific that this was one of the most important milestones of the project’s evolution.Device Design: Stage 1(Initial Microchannel Design Concept)• Objective– To create an initial design conceptfor a multilayer micro fluidic device• Initial design elements–90oorientation of fluid layers– Vertical interconnects at channel intersections– Each layer has same design- reduces number of molds– Versatility of fluid pathsI/OI/OBottom layerMiddle layerTop layerConcept good, reasonably explained here.Device Design: Stage 1 (Initial Microchannel Design Concept)Materials– Stackable PDMS layers– Silicon substrate–SU-8 moldsProcesses– Create a channel mold and an interconnect mold using SU-8 – Create PDMS layers from SU-8 mold: two layers from channel mold, one interconnect layer– Stack layers on substrate starting with a channel layer, interconnect layer and second channel layer at 90oorientationWell explainedDevice Design: Stage 2(Modified Microchannel Design)Device Objective– To test the viability of a two-level passive micro-fluidic deviceModifications from Stage 1– Moved reservoir positions to fit existing packaging– Created discrete flow paths to test flow on individual layers and between layers– Increased all dimensions to facilitate fabrication and testingDevice Logic– Five distinct fluid paths– 11 I/O– Two distinct channel levels– One interconnect level– One top cover levelGoodReservoir (I/O)InterconnectDevice Design: Stage 2(Modified Microchannel Design)Device Geometry– Chosen for process compatibility– Rectangular micro-channels– Square interconnects– Circular reservoirsMaterials– SU-8 used as a mold for the PDMS layers– All PDMS layers thenstacked on a Silicon substrate0.4 cmReservoir Diameter1000µmInterconnect Depth1000µmInterconnect Width500µmMicro-channel Width100µmPDMS Layer HeightValueCritical DimensionA cross-sectional sketch, with dimensions noted, might have been better than a chartDevice Design: Stage 2(Modified Microchannel Design)PDMS• Mix PDMS (Sylgard 184,


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