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Objective
Objective
Design a proof-of-concept device that utilizes acoustic waves and cost-effective manufacturing methods to generate droplets < 40 microliters (μl) in volume.
Design a proof-of-concept device that utilizes acoustic waves and cost-effective manufacturing methods to generate droplets < 40 microliters (μl) in volume.
Concept
Concept
A waveform generator is used to send a pulse to a piezoelectric element (PZT), which causes acoustic vibrations, causing fluid in a reservoir to expel out of a nozzle in the form of single droplets.
Design
Design
The droplet generator design aims for cost-effectiveness and ease of fabrication. It comprises five key elements: a linear solenoid actuator, piezoelectric buzzer, fluid chamber, nozzle, and adjustable fluid reservoir.
The piezoelectric buzzer, along with its relevant electrical components, attach to the fluid chamber using RTV silicone sealant. The linear solenoid actuator is fixtured concentrically above the piezoelectric buzzer. The fluid chamber is a 3D-printed piece that “funnel” fluid down to a hole where the nozzle attaches via an o-ring seal. The fluid reservoir is also constructed via rapid prototyping methods. Various off-the-shelf nozzles of varying diameters are compatible with this design (0.2 mm - 1.0 mm).
Theory
Theory
For static equilibrium, this equation must be true:
|Δh| ≤ 2σ/ρga
σ: surface tension
ρ: density of fluid
g: gravitational constant
a: radius of nozzle outlet
smaller nozzle outlet ⇒ ↑|Δh|
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