Microelectronic Thermal Valve Using Surface Tension for Fluid Ejection
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Solution Overview
Problem
Current technologies struggle to efficiently release small amounts of fluid at micro-scales in a continuous manner for specific periods of time, particularly in applications like inkjet printing and spacecraft propulsion, due to the complexity of motor assemblies and the inefficiency of heating and vaporization mechanisms.
Innovation Solution
A propulsion system using a capillary-controlled micron-sized nozzle with a shutter assembly actuated by electrostatic forces, which utilizes surface tension to maintain valve closure and heat-induced vaporization for controlled fluid release, integrated with a resistance temperature device for precise temperature sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If inkjet heating and vaporization mechanism is used to propel droplets, then droplet ejection is achieved, but continuous release for short periods at high velocity is not possible
Solution Approach 1:
The patent changes the operational parameter from cyclic heating-cooling to continuous heating with mechanical valve control. The thermal valve maintains continuous heat application while using a mechanical valve to control fluid release timing, enabling continuous release capability without the limitations of vapor bubble contraction cycles.
Solution Approach 2:
The patent replaces the thermal-mechanical coupling system (where vapor bubble contraction drives refilling) with a dedicated mechanical valve system. This mechanical valve independently controls fluid release timing without relying on thermal cycle completion, decoupling the release mechanism from the heating cycle limitations.
2Productivity
If peristaltic pump is used to separate and pump small amounts of fluid, then fluid transport is achieved, but complex motor assembly and control are required
Solution Approach 1:
The patent replaces the peristaltic pump's complex motor-driven roller mechanism with a thermal valve system that uses thermally-actuated shape memory alloy elements. These elements open and close the valve aperture in response to temperature changes, eliminating the need for motors, gears, and complex control systems while maintaining precise small amount fluid release capability.
Solution Approach 2:
The patent changes the actuation mechanism from mechanical rotation and compression to thermal response. Shape memory alloy elements change their physical state in response to temperature changes, providing a simpler, solid-state actuation mechanism that eliminates moving parts associated with motors and mechanical linkages.
3Force
If high pressure liquid propellant system is used for spacecraft propulsion, then thrust is generated, but mass ratio is reduced
Solution Approach 1:
The patent changes the propellant delivery parameter from high pressure to low pressure operation. By using a thermal valve to control release timing and a capillary-driven or gravity-assisted feed system, the spacecraft can generate thrust without requiring heavy pressure vessels and high-pressure storage systems, thereby improving the mass ratio.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves stable and repeatable thrust with high thrust-to-power ratios, efficient energy use, and reliable operation, suitable for spacecraft propulsion systems like picosats, with volumes under 2 cubic centimeters and masses under 2 grams, and power consumption under 400 mW.
Implementation Method 1
a heater that is configured to heat liquid surrounding it causing a rapid vaporization
Implementation Method 2
The chamber is then refilled by the next payload by surface tension and a negative pressure caused by contraction of the vapor bubble
Implementation Method 3
A propulsion system using a capillary-controlled micron-sized nozzle with a shutter assembly actuated by electrostatic forces
Implementation Method 4
integrated with a resistance temperature device for precise temperature sensing
Data Source
AI summary
A microfabricated valve with no moving parts. In one embodiment, the valve includes a reservoir of a liquid that is in fluid communication with an outlet channel having a throat that is less than 100 microns wide. Preferably, the channel is an elongated slit. The configuration of channel is adapted and configured such that surface tension of the liquid prevents flow out of the channel. A heater increases the temperature of the meniscus of the fluid, until a portion of the fluid is ejected from the channel. The ejection of the fluid creates both a thrusting effect and a cooling effect.