Figure :Schematic of the thermally controlled valveThermally Activated ValvesThermally Activated ValvesThe thermally activated valve is set up in a similar manner to the gas valve that was constructed. In the gas valve, an external source controls the pressure of a gas line. The change in pressure causes a flexible PDMS membrane to deflect creating a change in the flow state of the channel. Instead of a gas line, the thermally activated valve uses an isolated enclosure of a volatile liquid. In lieu of the external control, this valve uses an electrically controlled resistive heater. The valve works under the principle that an increase of heat will cause the liquid to boil. The boiling will then cause an increase in pressure as the gas forms and expands. The increased pressure will push on all walls of the enclosure equally, however because the top of the enclosure is the thin membrane, the top will flex upward hitting the stopper and therefore closing the channel. To open the channel all that needs to be done is for the heater to be turned off. Once no more heat is being entered into the system, the existing energy will leave and the gas will condense back into liquid form. To reduce the amount of heat required to heat the liquid to boiling, a highly volatile substance should be used. In a similar experiment (www.wimserc.org/Downloads/bioAR.pdf) cylco pentance was used. For that experiment only a 7o rise was needed to create a 6.5 Kpa pressure change. Assuming a similar heat to pressure SU-8PDMS Flex LayerPDMS Fluid LayerSU-8 Bottom LayerHeaterFigure :Schematic of the thermally controlled valveratio was attainable, the thermally activated valve would be a feasible option for electrical
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