Microelectronic Thermal Valve for Stable Capillary Thrust Control
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Solution Overview
Problem
Current technologies face challenges in achieving continuous and efficient fluid release at micro-scale volumes for specific periods of time, particularly in applications requiring high release velocity and reliability, such as in micro-satellite propulsion systems, where existing solutions like inkjet technology are impractical for continuous operation.
Innovation Solution
A propulsion system utilizing a capillary-controlled water nozzle with electrostatically actuated shutters and resistive heaters, which exploits surface tension and heat transfer to manage fluid flow, enabling precise and repeatable thrust control with a high thrust-to-power ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If inkjet technology is used to jet small amounts of fluid, then droplet ejection is achieved, but continuous release for short periods at high velocity is not possible
Solution Approach 1:
The patent changes the physical state of the fluid from liquid to vapor through controlled heating, enabling continuous flow. The heater maintains the fluid in a vapor state allowing sustained ejection, while the capillary structure controls the vapor flow rate. This phase change parameter enables continuous operation unlike inkjet's cyclic liquid-vapor-liquid process.
Solution Approach 2:
The invention implements continuous useful action by maintaining a constant heat source that sustains vaporization and a continuous vapor flow through the capillary channel. The heater remains active during the entire release period, providing uninterrupted vapor ejection, eliminating the need for cyclic heating and cooling phases required by inkjet technology.
2Measurement precision
If capillary control is used for micron-sized nozzle, then precise thrust control is achieved, but meniscus instability causes uncommanded impulses
Solution Approach 1:
The patent replaces the mechanical/physical meniscus-based flow control with a thermal field-based control system. Instead of relying on surface tension and meniscus position, the invention uses a heater to control vapor generation and pressure, which drives fluid ejection. This substitution of thermal control for capillary-meniscus control eliminates meniscus instability while maintaining precise thrust control through temperature regulation.
Solution Approach 2:
The invention exploits the phase transition from liquid to vapor to create a stable flow mechanism. The heater induces controlled vaporization, and the expanding vapor provides stable pressure to drive fluid through the capillary channel. This phase-change-driven mechanism replaces the unstable meniscus-based liquid flow control, providing reliable and commandable thrust.
3Productivity
If heater is used to vaporize liquid, then fluid ejection is achieved, but energy consumption increases
Solution Approach 1:
The patent applies heating locally at the capillary inlet rather than heating the entire fluid reservoir. This localized heating approach minimizes energy consumption by heating only the small volume of fluid needed for vaporization and ejection, rather than heating large amounts of liquid as in conventional systems. The heater is positioned to create vapor exactly where needed to drive flow through the capillary.
Solution Approach 2:
The invention uses vapor pressure generated by localized heating to drive fluid ejection, creating a pneumatic-driven flow system. The vapor expansion provides the driving pressure, eliminating the need for mechanical pumps or high-pressure liquid systems. This pneumatic mechanism achieves efficient fluid release with minimal energy input compared to mechanical or high-pressure alternatives.
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 values with a high thrust-to-power ratio, efficient energy use, and integrated cooling, suitable for small spacecraft like nano and picosats, while addressing issues of meniscus instability and uncommanded impulses.
Implementation Method 1
at least one heater positioned at the first region, the heater configured to heat the fluid causing ejecting of the fluid through the channel
Implementation Method 2
the width being sufficiently small such that surface tension of the fluid to be ejected would prevent free flow of the fluid out of the channel
Implementation Method 3
a plurality of small chambers, generally formed by a photolithography process are used to propel a droplet of ink out of the printer an on to a medium. Each chamber contains a heater that is configured to heat liquid surrounding it causing a rapid vaporization.
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.