Microfluidic Valve Innovation Jo Falls Porter, RET Fellow 2009 West Aurora High School RET Mentor: Dr. David T. Eddington, PhD NSF- RET Program Introduction  Microfluidic devices are used extensively in biochemical engineering, medical, and research laboratories.  A need exists for a cost effective valve that can be easily fabricated in the lab.  This valve design would allow variable flow restriction, not simply “on/off” capability.  This valve is designed to operate in devices made of Poly(dimethylsiloxane) (PDMS), a flexible silicone polymer typically used in microfluidic devices.  This valve would provide advantages in processing speed and availability of analyses procedures. Purpose Materials and Methods  Valves filled with PDMS and no tips were most effective. Further testing is recommended using slides with thin PDMS coating as base.  Hollow valves were least effective and no further testing is recommended.  Valves filled with PDMS having tips were not effective at the pressures used for this study, but further testing using only gravitational pressure is recommended. Special thanks to Dr. David Eddington, Microbioengineeering Lab Director, Marie Elena Brett and lab colleges Prof. Andreas Linninger, RET Director Funding by NSF EEC Grant Chemical and Bioengineering Program UIC Microfluidic Devices Valve Design Valve Design Testing Testing Microfluidic devices were fabricated in a 3 step process. First by making a mold, then creating the cast, and finally attaching the cast to a glass slide. The mold was created a Soft lithography process by controlled spinning of photosensitive resists (SU-8) on to a Si wafer, UV exposure for cross-linking and washing to remove non-linked resist. The casts were made by mixing PDMS and binder, removing bubbles, pouring PDMS into the mold and then baking. The cast were then removed from the mold, cut, ports punched and finally attached to a glass slide using a plasma wand. Valves were fabricated from 11 gage needle points, syringes, and PDMS. A Dremel tool was used to cut notches into needle points. Syringes were used to fill needle points with PDMS. Valve tips were fabricated using thin transparencies, blades, microscope imaging and PDMS. An automatic syringe pump was used to provide constant pressure to syringe. Blue dye was used to fill one syringe and a second syringe was filled with yellow dye. Tubing connected the syringes to the microfluidic device and the test valve was placed in the device port. Pressure was set at.026 cm3/minute. The movement was observed using a microscope and images taken to record results. Switches and valves are important in controlling fluid flow in microfluidic systems. Existing methods include use of electrodes, screws, two layered cross channels designs with pneumatic pressure switches, devices made of pH sensitive compounds, others that electrochemically generate micro bubbles or thermally cause microspheres to expand as a means of controlling fluid flow through tiny channels of micro system devices. Despite the range of methods and devices currently used, the need exists for a valve which is simply effective, yet simple to construct and operate. symscape Motivation This is an account of the design, fabrication and testing techniques used to construct a valve to meet this need. To design and fabricate a simple yet effective valve to be used in microfluidic devices. Results and Conclusions Valve Open Applications and Acknowledgements A lesson will be developed for high school chemistry students. Students will use PDMS to make a simple microfluidic devices and observe concentration changes.