Power Microsystems

Radiofrequency identification (RFID), especially passive RFID, is widely used in industrial applications to track and trace products, assets, and material flows. As technology advances, the trend toward increasingly miniaturized RFID sensor tags is expected to continue, though miniaturization poses challenges for maintaining adequate communication coverage. Recent efforts have explored the use of metamaterials in RFID technology to enhance power transfer efficiency by leveraging their unique ability to manipulate electromagnetic waves. In particular, metamaterials are finding growing applications in far-field RFID systems. Here, we present the development of a magnetic metamaterial and local field enhancement package that significantly boosts near-field magnetic strength, resulting in a substantial increase in power transfer efficiency between reader and tag antennas. Applying this magnetic metamaterial and local field enhancement package to near-field RFID technology provides high power transfer efficiency and expanded communication coverage, opening new possibilities for the rapidly growing Internet of Things (IoT) landscape.

The objective of this research is to develop a highly sensitive, mechanically robust, and mass-producible gas micro-detector designed for integration into a portable micro-gas chromatographic system capable of competing with the performance of traditionally laboratory instrumentation. The approach involves optimizing the performance and sensitivity of the detector by modeling, analyzing, and experimentally validating various heat flux pathways from the detector’s active element. In addition, the modeling and testing processes are conducted to ensure the detector’s resilience to mechanical shock and its compatibility with a wide range of thermal and chemical operating environments. In the pursuit of novel gas sensors and detection mechanisms, limited effort has been directed toward improving thermal conductivity detectors—one of the oldest gas sensor technologies. However, thermal conductivity detectors are particularly well-suited for miniaturization, as they are sensitive to the concentration of components in a mixture rather than the total sample mass—a limitation of flame ionization detectors and mass spectrometers. As a result, miniaturized gas chromatographic systems employing thermal conductivity detectors can maintain functional sensitivity while handling smaller sample volumes, with the added benefits of lower power consumption and improved mechanical robustness. The development of a highly sensitive, yet simple and durable detector—integrated into a miniaturized system—positions gas chromatography to have a broader impact across various fields. These include point-of-care health diagnostics, homeland security, industrial process control, and geological exploration.

Our research explores the mechanical integrity and thermal performance of thin films and nanostructured materials, with a focus on applications in microelectromechanical systems (MEMS), integrated circuits, and emerging nanoscale technologies. We investigate how materials such as plasma-enhanced chemical vapor deposited (PECVD) silicon oxide, silicon nitride, silicon oxynitride, and silicon oxycarbide respond to mechanical loading and thermal cycling. Using techniques including nanoindentation, microbridge testing, and wafer curvature analysis, we probe stress evolution, creep, plastic deformation, and fracture toughness—revealing strong dependencies on film thickness, composition, microstructure, and post-deposition annealing. Our recent work also examines nanoscale thermal transport, studying how localized heating and interfacial phenomena—such as plasmonic resonances and quasi-ballistic phonon transport—influence heat dissipation in materials like graphene and carbon nanotubes. These investigations deepen our understanding of material behavior at small scales and guide the development of robust, thermally efficient materials and structures for next-generation electronics, sensors, and power and energy systems.

In micro-satellites, a wide array of delicate instruments must be integrated into a compact and constrained space, presenting significant challenges in thermal management, particularly for active and remote cooling. Silicon-based micropump arrays have emerged as an attractive solution due to their fabrication simplicity, minimal cryogen charge requirements, and capacity to maintain instruments within a narrow cryogenic temperature range. The performance and longevity of these micropumps are critically dependent on two key factors: pumping capacity, which relates to diaphragm deflection, and reliability, which is governed by mechanical stress and fatigue behavior. Both characteristics are heavily influenced by the silicon diaphragm, one of the most essential components of the system. This research focuses on evaluating the pumping capacity and operational reliability of silicon-based micropumps under cryogenic conditions, specifically for micro-satellite applications. Fatigue testing was performed over 1.8 million cycles without evidence of structural degradation, demonstrating the suitability of silicon as a robust and reliable material for long-duration operation in extreme cryogenic environments.

This body of work demonstrated the feasibility of silicon-based gas turbine engines at the microscale by realizing fully integrated microfabricated structures capable of combustion, energy conversion, and high-speed rotation. Using deep reactive ion etching (DRIE) and precision wafer bonding, complex multi-wafer assemblies were developed to incorporate fuel plenums, injectors, catalytic and non-catalytic combustors, and static turbine components–all within volumes smaller than a cubic centimeter. Stable hydrogen and hydrocarbon combustion was sustained in micromachined chambers, achieving exit gas temperatures exceeding 1600 K—marking one of the first demonstrations of sustained microscale flames in silicon. Microfabricated rotors, supported by gas-lubricated or self-acting thrust bearings, reached rotational speeds above one million RPM, delivering power densities comparable to conventional turbomachinery. Additional innovations included thin-film resistive igniters and through-wafer electrical interconnects that enabled localized heating and sensing. Together, these advances established the potential of MEMS-based turbomachinery for compact, high-speed energy conversion and propulsion systems.

This work advanced the microfabrication techniques necessary to construct three-dimensional silicon-based microsystems with robust mechanical and thermal performance. Deep reactive ion etching (DRIE) was optimized to create high-aspect-ratio trenches up to 500 µm deep, with improved sidewall smoothness and profile control. Process refinements addressed both global and local etch non-uniformity—critical for minimizing rotor imbalance in high-speed rotating devices. Multi-stack silicon wafer bonding was systematically developed and characterized to support complex multilayer assemblies, with particular attention to interface quality, defect propagation, and thermomechanical stability. The behavior of thick plasma-enhanced chemical vapor deposition (PECVD) oxide films was extensively studied to understand how deposition and thermal processing affect residual stress, fracture risk, and wafer bowing. Through detailed characterization using profilometry, interferometry, electron microscopy, and fracture mechanics modeling, this research established key relationships between processing parameters and material behavior. These fabrication strategies enabled the reliable construction of MEMS structures for applications in energy conversion, sensing, and actuation.