Microscopic forced-flow heat-transfer systems containing heat exchangers, flow channels, electrostatically driven peristaltic pumps, and related components have been proposed. These systems would be made largely of silicon, by use of micromachining processes similar or identical to those used to make integrated circuits. These microscopic heat-transfer systems could thus be made as integral parts of integrated circuits: For example, charge-coupled-device (CCD) imaging circuits in infrared cameras could be cooled very effectively by incorporating such systems to circulate cryogenic fluids within the CCD substrates.
The figure illustrates a dual-cavity push-pull embodiment of an electrostatically driven peristaltic pump. The pump channels would be etched into silicon substrates, which are bonded together with an electrically conductive flexible membrane sandwiched between them. The channels would be lined with electrically conductive strips covered with electrically insulating material and separated from each other by electrically insulating barriers. By applying a suitable voltage between the membrane and the conductive strips of each channel in succession, one would cause the membrane to be electrostatically pulled into the channel at successive positions along the channel. Dual interlaced and interlocked shift registers enable alternate inversions of bit-stream sequences and multiple membrane "bubbles" that move down the channel, pushing entrapped fluid in front of each membrane "wall" and pulling the fluid behind each membrane "wall." This pump architecture represents a true two-dimensional analog of a peristaltic mechanism that is valveless, impervious to gas-bubble entrapment, does not require priming, and is self purging. The device is a digital pump that may be single-stepped to function as a valve or, by counting the number of clocked bits, is a precision flowmeter.
A heat exchanger consisting of micromachined channels in a thermally conductive material would be designed to maximize heat-transfer surface area and to provide effective convective coupling of heat between the pumped fluid and the channel surfaces at the expected flow speeds. The use of microscopic channels would make it possible to achieve low conduction and convection losses, with consequent high thermal coupling and short characteristic times for decay of thermal transients.
This work was done by Frank T. Hartley of Caltech for NASA's Jet Propulsion Laboratory.
This is the invention of a Caltech/JPL employee, and a patent application has been filed. Inquiries concerning license for its commercial development may be addressed to
the inventor:
Frank Hartley
JPL
MS 125-177
4800 Oak Grove Drive
Pasadena, CA 91109
(818) 354-3139
Refer to NPO-19093
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Microscopic heat exchangers, valves, pumps, and flowmeters
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Overview
The document discusses innovative microscopic heat-transfer systems developed by Frank T. Hartley at NASA's Jet Propulsion Laboratory. These systems incorporate heat exchangers, valves, pumps, and flow meters, primarily fabricated using micro-machining techniques similar to those used in integrated circuit production. The primary focus is on the design and functionality of electrostatically driven peristaltic pumps, which can effectively transport fluids or vapors at a wide range of flow rates.
The proposed peristaltic pump architecture features channels etched into silicon substrates, with a flexible electrically conductive membrane sandwiched between them. By applying a voltage, the membrane is electrostatically pulled into the channels, creating peristaltic waves that move the fluid along. This design is notable for being valveless, self-purging, and impervious to gas-bubble entrapment, making it suitable for precision applications such as flow metering and as a digital pump.
The document highlights several advantages of these microscopic systems. They exhibit minimal thermal conductive and convective losses due to their micro-dimensional structure, resulting in high thermal coupling and short thermal time constants. This efficiency allows for effective cooling of integrated circuits, such as CCDs in infrared cameras, by circulating cryogenic fluids directly within the substrates. Additionally, the systems are not reliant on gravity or density gradients, making them ideal for use in space environments, such as on the Space Shuttle or the International Space Station.
The heat-transfer systems can be bonded to the surfaces of integrated circuit chips or power packs, providing direct heat dissipation without the need for forced ventilation or orientation constraints. The document emphasizes the potential for these devices to replace traditional heat sinks and ducted air circulation methods, offering a quieter and more efficient solution for thermal management.
Overall, the work represents a significant advancement in the field of micro-scale fluid dynamics and thermal management, with potential applications across various industries, particularly in aerospace and electronics. The document concludes by noting that a patent application has been filed for this technology, indicating its commercial viability and the potential for further development.
