Paper Microfluidic Devices Design Automation for Paper Microfluidics with Passive Flow Substrates Joshua Potter, William H. Grover, and Philip Brisk GLSVLSI 2017

Outline Introduction & Motivation The Design Framework Experimental Efforts Future Work

Introduction & Motivation Design Automation for Paper Microfluidics with Passive Flow Substrates

Introduction The most familiar application of paper microfludics is the home pregnancy test Additional tests exist for urinalysis (e.g. diabetes) Low cost Materials and labor mostly Reduces the need for sophisticated testing equipment Point of care Promises to allow for low-cost, in the field diagnostics and treatments

Motivation The promise of a greater array of diagnostics and treatments By reducing the amount of man hours needed to develop and test designs Adaptive Diagnostics Potential for greater efficacy, efficiency, and accuracy of diagnostics and treatments Additional design constraints Fluid dynamics involving capillary action, backflow pressure, volume and flow limitations need to be accounted for in design and fabrication Environmental factors such as temperature, humidity, barometric pressure may also affect devices

Motivation Increasing complexity a) Symbolized trigger valve b) Time-sequential photographs showing that the gated fluid (blue) was released by the triggering fluid 1 Three fluid lateral flow test based on four fluidic valves 2 1) Chen, Hong, et al. "A fluidic diode, valves, and a sequential-loading circuit fabricated on layered paper." Lab on a Chip 12.16 (2012): 2909-2913. 2) Gerbers, Roman, et al. "A new paper-based platform technology for point-of-care diagnostics." Lab on a Chip 14.20 (2014): 4042-4049.

Motivation Hand-designed and fabricated Requires significant work to produce modifications and iterations Need for a dynamically generated, parameterized approach Programmable micropad for urinanalysis 3 3) A. W. Martinez, S. T. Phillips, Z. Nie, C.-M. Cheng, E. Carrilho, B. J. Wiley, and G. M. Whitesides. Programmable diagnostic devices made from paper and tape. Lab-on-a-Chip, 10(19):2499{2504, 2010.

fMUX A version of the multiplexer presented by Martinez, et al.3 built in our framework Parameterized to allow the end user to specify the number of channels to be selected from The framework generates the necessary layers and channel placements from a minimum of 2 channels to a maximum based on the size of the substrate(s) 2, 4, 6 and 8 channel fluidic multiplexers (fMUX) 3) A. W. Martinez, S. T. Phillips, Z. Nie, C.-M. Cheng, E. Carrilho, B. J. Wiley, and G. M. Whitesides. Programmable diagnostic devices made from paper and tape. Lab-on-a-Chip, 10(19):2499{2504, 2010.

The Microfluidic Framework Design Automation for Paper Microfluidics with Passive Flow Substrates

Framework Overview Stand-alone application developed in C++ Analogous in many ways to chip fabrication Design process accounts for various conditions and constraints Fluids and Substrates are characterized within the framework Desired device(s) with parameters are specified and then the framework generates a layout (if viable) and output to standard printing formats or JSON netlists

Design Automation for Paper Microfluidics with Passive Flow Substrates Experimentation Design Automation for Paper Microfluidics with Passive Flow Substrates

Experimental Setup Wax-based printer Cellulose-based paper substrates Hydrophobic wax inks allow for printing fluid barriers Reheated wax penetrates paper to create barriers for the entire thickness of the paper Cellulose-based paper substrates Initial tests utilize known paper substrates for consistency

Initial Demonstration Tests A rough, simple pattern printed on a substrate saturated with water dyed with food colorant Edges folded under to suspend substrate above lab surface Otherwise, when fluid saturates substrate, fluid will flow across lab surface Surface not level or even causing erratic fluid travel

Raceway Calibration Device Designed to test various channel widths Examine volume to distance travel Variable measurement ticks for in situ measurement of fluid travel

Border Containment Tests Initial experiment using the Raceway Calibration Device Channels specified with 2.0mm borders Fluid containment failure due to uneven substrate surface and non-level conditions Demonstrated need for testing rig

Test Rig Developed and constructed by the authors to provide level surface to substrate under test Substrate tautly suspended on two sides Keeps fluid and substrate from contacting lab surface

Bullseye Calibration Device Designed to test fluid travel at various orientations Can test sink-to-source or source-to-sink Variable channel lengths and widths, each independently specified Radial measurement ticks from source to sinks

Border Containment Test using Bullseye Device 0.5 mm 1.0 mm 1.5 mm, some leakage upper right 2.0 mm

Design Automation for Paper Microfluidics with Passive Flow Substrates Future Work Design Automation for Paper Microfluidics with Passive Flow Substrates

Future Work Capture of environmental conditions within the framework to allow for accurate simulation within the framework prior to fabrication to validate generated devices Create profiles of various fluids and substrates to determine both successful placement of components and viability of routing solutions of layouts

Future Work Integrating design automation algorithms such as placement and routing of paper microfluidic components within the physical constraints of passive flow and flow-resistant substrates Explore the applicability of printable circuits for control of fluids over hydrophobic surfaces

Design Automation for Paper Microfluidics with Passive Flow Substrates Conclusion Design Automation for Paper Microfluidics with Passive Flow Substrates

In Conclusion Paper-based microfluidics: provide portable laboratory tests without expensive actuation equipment reduce the cost of fabricating new devices and performing diagnostic tests The authors’ software framework: can simplify and automate the design process helps device designers more rapidly prototype new designs and applications through automation Reduces the time and materials needed to develop and iterate devices

Acknowledgements National Science Foundation This work was supported in part by NSF Award #1423414.

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