DARPA’s HOTS Program to Develop Sensor Microelectronics for Extreme Temperatures

DARPA has launched the new High Operational Temperature Sensors (HOTS) program that will "leverage recent advances in wide-bandgap transistors, demonstrations of thermally robust transducer materials, and insight from heterogeneous integration techniques to overcome the technical challenges and form highly-integrated, thermally-hardened sensors," according to a recent announcement from the agency. (Image: ASB63/Adobe Stock)

Modern technologies are laden with sensors – a now-customary fact of life in much of the world. On smart watches and phones, and in cars and homes, sensors help monitor health, adjust various settings for comfort, and warn of potential dangers. More widely, sensors are deployed across countless commercial and defense systems, including in the oil and gas sector, the automotive industry, alternative energy sources, geothermal applications, and aviation and aerospace.

In these broader industrial contexts, the capabilities of sensors can be inhibited by thermal limitations. A sensor may theoretically be able to process inputs such as speed, pressure, or the integrity of a mechanical component, but inside a turbine engine, temperatures far exceed what any existing sensor can withstand.

The Defense Advanced Research Project Agency’s (DARPA) new High Operational Temperature Sensors (HOTS) program will work toward developing microelectronic sensor technologies capable of high-bandwidth, high-dynamic-range sensing at extreme temperatures.

“Many of the defense and industrial systems that rely on sensors experience harsh environments beyond the capability of today’s high-performance physical sensors. That means these systems have to be designed and operated with reduced performance and excessive margins – they’re limited by the uncertainty of their thermal environments,” said Dr. Benjamin Griffin, program manager for HOTS. “However, if we can design, integrate, and demonstrate high-performance physical sensors that can operate in high-temperature environments, we can advance toward systems that perform at the edge of their capability instead of the limits of uncertainty.”

In development of next generation turbine engines or high-speed flight, thermal restrictions can hamstring progress. For example, high-performance pressure sensors are needed to capture complex flow dynamics in extremely high temperature environments (i.e., 800 °C or 1472 °F).

Today, sensors that can withstand thermally harsh conditions are limited to low-sensitivity transducers located in hot zones coupled via noisy electrical connections to remote, temperature-constrained, silicon signal-conditioning microelectronics in cold zones. The resulting integrated sensors lack the combination of frequency bandwidth and dynamic range essential for high-temperature missions.

Physical sensors that can overcome these limitations and optimally perform in high-temperature environments – without additional thermal management – will enable critical operations that include monitoring stability and functionality in extremely hot system components. Combinations of emerging materials, fabrication techniques, and integration technologies that inform new types of transistors and transducers, are among the potential approaches the HOTS program hopes to demonstrate as a sensor module.

HOTS will hold a Proposers Day on May 31, 2023. In the federal register announcement of the HOTS program, DARPA outlines the program objectives for HOTS as seeking to resolve some of the limitations associated with transducers featured in high-performance microelectronic sensors available today.

"High-bandwidth, large-dynamic-range sensors typically combine high electromechanical sensitivity, limited-bandgap transducers with high gain-bandwidth product, silicon complementary metal-oxidesemiconductor (CMOS) transistor signal-conditioning microelectronics using low-loss integration technology. However, these technologies are constrained by intrinsic material limitations to operate in low-temperature zones (<225 °C1 ambient temperature) due to intrinsic material limitations at elevated temperatures of the high-temperature platforms in which they are deployed (e.g., turbine engines)," DARPA writes in the announcement.

“If you look at the progress of cars alone, we’ve seen sort of a nervous system of sensing evolve, providing visibility and knowledge of what’s happening across the platform. Applying the same concept to larger-scale systems in harsh environments will offer tremendous benefits for the future system capabilities,” Griffin said.

Further HOTS program details will be available in a forthcoming Broad Agency Announcement.