A newly patented invention could provide the Department of the Air Force (DAF) with smaller, lighter, lower-power, and potentially lower-cost chip scale microelectromechanical components for aircraft, spacecraft, satellites, unmanned systems, and fielded electronics.
Dr. Hengky Chandralahim is an associate professor in the Department of Electrical and Computer Engineering at the Air Force Institute of Technology (AFIT). He is also the director of the AFIT Nanofabrication and Characterization Facility. He recently received a patent from the United States Patent and Trademark Office for “ion irradiation of microelectromechanical resonators” technology.
The idea originated in a broader research question: How do heavy ions affect piezoelectric microelectromechanical resonators intended for spacecraft, nuclear systems, and other radiation environments? Existing studies usually compared devices only before and after exposure, leaving engineers with little information about how resonant frequency, quality factor, motional resistance, and electromechanical coupling changed as radiation dose accumulated. Dr. Chandralahim and his collaborators addressed this gap with theoretical analysis, radiation-transport simulations, equivalent-circuit and device modeling, and in situ measurements during irradiation.
As the models and experiments were refined against one another, the team observed that controlled ion exposure created atomic-scale defects that altered the resonator’s elastic, piezoelectric, and dielectric properties. The most important finding related to a substantial increase in effective electromechanical coupling, which governs electrical-to-mechanical energy conversion and strongly influences resonator and filter performance.
That finding led to the invention. The team recognized that irradiation could be used as a post-fabrication tuning method to enhance coupling in a microelectromechanical system, reducing the need for a full redesign and fabrication cycle. The team then developed this finding into a post-fabrication method for modifying completed resonators and coupled-resonator filters.
The post-fabrication process is somewhat like tuning a musical instrument after it has been built. Instead of changing the resonator’s shape or fabricating a new device, the team exposes it to a carefully controlled beam of energetic ions. These ions behave like microscopic billiard balls. As they pass through the resonator, they displace a small number of atoms and create controlled defects within its material layers. These atomic changes modify the material’s electrical, piezoelectric, and mechanical properties.
By selecting the proper ion type, energy, and dose, users can increase electromechanical coupling, which measures how efficiently the resonator converts between electrical and mechanical energy. The method can be used on individual resonators or coupled resonators that form filters, providing a practical way to tailor device performance after fabrication.
The DAF could benefit from this invention through increased availability of smaller, lighter, lower-power, and potentially lower-cost chip scale microelectromechanical components for aircraft, spacecraft, satellites, unmanned systems, and fielded electronics. Microelectromechanical resonators serve as basic “building blocks” in many systems. In sensing, they can support accelerometers, gyroscopes, vibration sensors, and other instruments used for platform health monitoring and inertial navigation. In timing, they can serve as compact frequency references and oscillators that keep electronic systems synchronized. In radio-frequency processing, they can be used in filters that select desired communication, radar, or electronic warfare signals while rejecting unwanted frequencies.
The patented technology could also have commercial value wherever compact microelectromechanical resonators are used for sensing, timing, navigation, and radio-frequency signal processing.
One possible follow-on invention is selective irradiation, in which only specific regions of a resonator or selected devices on a wafer are exposed. This could allow engineers to adjust electromechanical coupling, capacitance, stiffness, or resonant behavior after fabrication, much like trimming an electronic circuit to meet its specifications.
Another possibility is a closed-loop process that combines a focused or scanned ion beam with real-time electrical measurements. The irradiation could stop automatically when the device reaches a desired performance target. Related inventions could use masks, different ion species, radiation energies, and doses to control where defects are created within material layers.
The method could also be adapted to other piezoelectric materials and extended to coupled-resonator filters, oscillators, sensors, and energy harvesters. Combining controlled irradiation with thermal annealing may provide an additional way to stabilize or partially adjust the resulting material changes.
The current work demonstrates conceptual viability, but additional testing is needed before broader application is possible. Researchers need to evaluate other electromechanical transducers – including piezoelectric, electrostatic, thermal, and electromagnetic microelectromechanical devices – to determine how controlled irradiation affects their operating characteristics. Researchers also need to test different radiation types – such as protons, neutrons, gamma rays, X-rays, and other heavy ions – over a wider range of energies, dose rates, and total doses.
Material studies are equally important. Different piezoelectric films, substrate materials, electrodes, and dielectric layers may form different atomic defects and therefore respond differently. Microscopy, spectroscopy, and electrical measurements can help connect those material changes to device performance and long-term stability.
Future work should also determine how repeatable the process is, how much of the change remains after annealing or long-term operation, and how to balance increased electromechanical coupling with changes in quality factor and electrical resistance. Finally, the method should be tested on complete filters, oscillators, sensors, and packaged systems under realistic operating conditions.
Dr. Chandralahim’s patent application was facilitated by AFIT’s local Office of Research and Technology Applications (ORTA). DAF ORTAs conduct outreach related to technology transfer and facilitate the development of formal technology transfer agreements, including patent licensing agreements, to ensure the protection of the DAF’s intellectual property interests regarding innovative technologies. The DAF Technology Transfer and Transition (T3) Program Office provides DAF ORTAs with training and guidance, and it also performs ORTA services for DAF laboratories lacking their own ORTA.
United States Patent and Trademark Office Patent #12,665,562