1. Microfluidics and Valve Design Mark Barineau Ryan Slaughter

2. Presentation Overview Lincoln Laboratory goals Micro- and Macroscale Fluidics Governing Physics Valve and Actuator Types Related Technologies Butane/LPG Properties FEA Intro

3. Critical Findings Distinction between microfluidics and microvalves Applicable valve, actuator, and sensor technologies have been developed Butane/LPG is a good choice

4. LL: Fuel Metering Valve Need compact, low-mass system to meter fuel flow in prototype TE microgenerator system –Relevant to other micropower applications, as well Design goals: –Automatic control to accommodate varying electrical loads –Compensate for fuel vapor pressure –Integration into fuel tank plumbing –Very low mass: < 10 grams including tank adapter –Very low power: < 50 mW –Operability with LPG fuels: butane and propane –Act as compact massflow controller

5. LL: Candidate Performance Specification SpecificationValueComments Target FuelButane, LPG Full scale massflow200 sccm Control Range20% to 100% and Off Valve should be capable of being commanded to these set positions using TBD electrical signal (PWM, analog, or other) Fuel Temp10C to 40CWide vapor pressure range is significant design challenge Accuracy+/- 20% of Set PointAverage over any 1 second interval Allowable Pulsation0 to 200% of FS 0 to 150% of FS 0 to 120% of FS 50 msec Power Consumption< 50 mW @ 3 to 6 VDC Includes any power dissipation for control signals Mass< 10 grams InterfaceTBDIn: LPG Fuel canister Out: Fluoropolymer tubing Electrical: Flying Lead

6. LL: Valve Concept Rough concept for initial performance requirements –Actual requirements driven by more thorough design review Pressure Regulator Low Frequency DC modulation Flow Regulator Pulse Width Modulated Valve Controller Fuel Pvap(T) Fuel Mass Flow Temp Flow SP

7. Valve Components Fluid reservoir Actuator Restrictive element Sensor(s) Controls Interconnects

8. Micro- vs. Macrofluidics Microfluidic—devices and/or flow characteristics Knudsen number –Kn<0.3, Continuity –Kn>0.3, Statistical mechanics

9. Fluids (2.005) Review Navier-Stokes Eq. Mass Continuity Reynolds Number

10. Working Fluid: Butane, LPG High heat of combustion (~50 MJ/kg) Stable storage and manipulation Clean burn Reliable, cost-effective valve solutions exist Safe for lab use => gas detection tools available

11. Butane Properties * Density: –2.46 kg/m3 gas (288 K) –600 kg/m3 liquid (272 K) (roughly half that of H20) MP: 135.4 K, BP: 272.6 K Flash Point: 213 K Auto-ignition Temp: 773 K Cost: ~0.70 $/gal *all values for 1 atm

12. Butane Properties

16. Fundamentals of FEA

17. Conclusions Microfluidics/Valve to Fluidics/Microvalve Applicable valve, actuator, and sensor technologies are available for our device Butane/LPG is a reasonable fuel

18. Next Steps System concept/design refinement –Confirm valving liquid or gas –Actuation –Closed Loop Sensing/Controls Learn from other groups (especially related to DFM)

19. Questions?