University:
Boston University
Course:
ENG ME 302 | Engineering Mechanics II
Academic year:

2024
Views:

367

Pages:

20
Author:

Lukas Stone

Pneumatic Valves “Quake” valve • Bilayer microfluidic chip. • Thin film separating two flow channels. • One channel: Fluid • One channel: Air (controlling) • Pressurized air deflects the thin film and closes the fluid channel. Pneumatic Valves “Quake” valve • Bilayer microfluidic chip. • Thin film separating two flow channels. • One channel: Fluid • One channel: Air (controlling) • Pressurized air deflects the thin film and closes the fluid channel. Pneumatic Valves “Quake” valve Pneumatic Valves “Quake” valve Push-down Valves • • • • Control lines above flow channels. Pressure flattens membrane valve down to seal. Suitable for low aspect ratio (1:10) & shallow (~10um) channels. • Flow geometry: 100um x 13um • Control geometry: 100um x 10-25um Applications: where fluid flow must be in contact with substrate (spotting DNA, patterned substrate, etc.) Push-up Valves • • • Control lines belowflow channels. Pressure deflect membrane valve up to seal. • Flow geometry: 100um x 13um-50um • Control geometry: 100um x 10-25um Applications: suspension of large particles (eukaryotic cells, large beads, etc.) Pneumatic Valves Pneumatic Pumps Multiple control channels – alternating pressure in/out. Peristaltic pumping: • Frequency dependent flow rate Mechanical Valves Flexible microfluidic device with single deformable arch. Stretching /bending the device reduces the arch height, partially opens the channel. Mechanical Valves Mechanical Valves Buckled arch in microfluidic chamber. Arch shape obtained from buckling analysis of elastica. Apex: Mechanical Valves Navier-Stokes Equations: …conservation of momentum… Continuity Equation: …conservation of mass… Stokes Equations: Neglect inertia & body forces Incompressible: Mechanical Valves Stokes Equations: Neglect inertia & body forces Incompressible: Dimensionless Parameters: Lengths: Velocities: Shape of the impingement: Pressure: Mechanical Valves Dimensionless Equations: Boundary Conditions: No slip Total flow rate is prescribed Perturbation Expansion: Shape of the impingement: Extended Lubrication Fluid flow through channels with variable geometry Extended Lubrication Theory Extended Lubrication Extended Lubrication Bioinspiration Large, rapid, reversible diaphragm deformation for fluid pumping. Electrical Valves Electrodes V Dielectric Fluid Electrodes At what voltage will the plate buckle? Radial strain in a dielectric elastomer Plane stress relation Linear stability analysis for a buckling plate Microfluidic Fabrication 1. Prepare the top substrate with the microfluidic channel. 2. Prepare the bottom substrate with all controlling channels. 3. Make the thin, dielectric film. 4. Bond the substrates on both sides of the dielectric film. • Film will buckle at the intersection between channels. 5. Fill the channels with conductive fluids. 6. Apply a voltage to induce buckling _ + Valving