Dr. Robert S. Okojie has numerous engineering contributions to high temperature aerospace technologies, in particular, electronic devices based on silicon carbide (SiC) semiconductors. His contributions to the design, fabrication, and packaging of high temperature electronics are of high importance and impact on a national scale.
He has been a national leader in the development of microelectromechanical (MEMS)-based silicon carbide pressure sensors for use near turbine engines and other high temperature, highly corrosive environments. Electronics to monitor pressure and temperature at propulsion systems has been a major goal of aerospace technology.
The NASA Glenn Sensors and Electronics Branch is developing silicon carbide as a material for advanced semiconductor electronic device applications. SiC-based electronics and sensors can operate in hostile environments (600 degrees C) where conventional silicon-based electronics (limited to 350 degrees C) cannot function. Silicon carbide’s ability to function in high temperature, high power, and high radiation conditions will enable large performance enhancements to a wide variety of systems and applications.
Dr. Okojie’s work has enabled packaging designs for the production of silicon carbide pressure sensors that can function reliably at turbine engines without degrading. This is a multidisciplinary challenge that requires an in-depth understanding of electronics, mechanics, physics and chemistry. The ability to integrate across these disciplines has been a hallmark of Dr. Okojie’s career.
His latest achievements have also included patented techniques for decoupling thermomechanical stress between silicon carbide sensors and their packaging as well as eliminating wire bonding altogether – advances that avoid the otherwise catastrophic failure of these devices during operation.
These techniques are now being licensed for use by a leading manufacturer of microsensors. He has extended his silicon carbide expertise to batch fabrication of silicon carbide laminates for advanced fuel injectors that satisfy international civil aviation standards. His advance enables the use of this high performance semiconductor in the active control of engine combustion. He has even developed the first accelerated stress test protocol published in the IEEE International Reliability Physics Symposium, the venue by which reliability testing is accepted by world industry.
These are the latest in an impressive list of Dr. Okojie’s achievements. Among his past successes, he demonstrated the world’s first thermally stable ohmic contact metallization on silicon carbide at record breaking temperatures for extended periods of time. In turn, this paved the way for high temperature sensors and electronics at these temperatures that can substantially improve safety and efficiency, as well as directly impacting the air quality around airports. His many patented device contributions extend to numerous MEMS structures that can reduce air and noise pollution, provide new deep well drilling tools, and supply sensors for the temperature and chemical extremes of aerospace environments.
Key Inventions
SiC Pressure Sensor Technology that enables the robust packaging of silicon carbide pressure sensors that can be inserted in closer proximity to a jet engine combustion chamber, thereby leading to increased accuracy in pressure measurement needed for more accurate validation of the computational fluid dynamics codes. This benefit extends to all applications for this type of pressure sensor – closer proximity leads to more accurate readings.
Development of High Temperature MEMS Packaging that removes two key technical barriers, decoupling of CTE mismatch and elimination of wire bonding and failures associated with it, enabling silicon carbide pressure sensors to monitor pressures in the high temperature (~600 degrees Celsius) sections of vehicles.
MEMS-based SiC Lean Direct Injection Array that reduces nitrogen oxides (NOx). Due to its near inert surface chemistry, Dr. Okojie’s new system eliminates warping and significantly reduces coking problems that plague the current NOx reduction systems.
Related Articles
NASA
- Center is Rich with Technological Challenges for Dr. Okojie: Dr. Robert Okojie, a researcher in the Sensors and Electronics Branch, is a testament to the quality of a research environment that nurtures talent and ability at NASA Glenn.
- NASA Technology Licensed for New MEMS Pressure Sensor: Glenn has licensed three patents, covering high-temperature, harsh-environment, silicon carbide (SiC) pressure sensors, to Endevco Corporation, San Juan Capistrano, Calif.
- NASA GRC – Silicon Carbide High Temperature Integrated Electronics and Sensors
- Sensors Increase Productivity in Harsh Environments
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