Research
Motivation.
Remember that only limited researchers have access to high-end micro-/nanofabrication facilitates worldwide.
Processes and materials we are currently relying on may not be the best out of available options.
We look for better processes for conventional micro-/nanofabrication materials and better materials
to realize high-performance transducers.
Research Interests
Large scale batch fabrication of nanostructures based on silicon self-assembly, Hydrogel based micro-/nanoelectromechanical systems, Materials and processing for flexible, stretchable, and wearable devices, Nanoscale 3D printing of organic and inorganic hybrids, 3D printing for biomedical applications, Multifunctional atomic force microscopy, Single molecule force/mass spectroscopy, High-precision Laser based manufacturing and metrology, Additive manufacturing, Heat transfer.
Current ongoing research topics
Annealing is a widely used technique in integrated circuits (ICs) and micro-/nano-electro-mechanical systems (MEMS/NEMS) to relieve stress in semiconductor materials, redistribute or activate dopants, repair ion-implantation damage, and promote interfacial reactions at metal contacts. Notably, annealing can also induce morphology changes in pre-patterned semiconductor structures to minimize surface energy. By using this behavior, diverse semiconductor micro-/nanostructures can be fabricated by combining standard etching and annealing processes. We develop wafer-attached or separated architectures using a combination of global and localized heating—structures that are difficult to realize with conventional fabrication process. These unique architectures enable the fabrication of high-quality semiconductor materials and high-performance micro-/nano devices.
Three-dimensional structuring of semiconductors is an important route to increase effective surface area and integration density in electronic and microsystem technologies. Photoelectrochemical etching enables wet-chemical fabrication of high-aspect-ratio meso- and macropore arrays by controlling the generation and transport of photogenerated carriers, providing an alternative to conventional dry etching. In combination with high-temperature annealing, which modifies stress and morphology of pre-patterned structures through surface-energy-driven shape evolution, this method allows control of pore and membrane geometries in monocrystalline substrates. These structures have significant potential for application in filtration membranes, vertical interconnects (vias), and multi-layer process integration in advanced micro/nano devices.
Silicon nanoparticles are becoming increasingly important as next-generation anode materials. However, a standardized process for the large-scale production of spherical silicon nanoparticles suitable for anode applications has not yet been established. Accordingly, our laboratory is investigating the aerosolization-based spheroidization mechanism with the goal of establishing a scalable mass-production process.
[Hyper-multimodal measurements with heater-integrated microchannel resonator]
Heater-integrated microchannel resonator (HMR) is a system that integrates its key components for the first time, enabling simultaneous resonant densitometry, viscometry, and resistive thermometry. It operates in two distinct modes based on the state of the fluid sample: a stationary mode, where the liquid remains static without flow, and a transit mode, where the liquid flows through the device. 1) In the stationary mode, pressure at the channel inlet and outlet is balanced to keep the liquid static. This mode leverages the dependence of temperature response and mechanical behavior during controlled pulsed heating on the thermophysical and mechanical properties of the liquid inside the channel. By measuring temperature and mechanical resonance changes over time at high power levels, thermophysical properties, including thermal conductivity (k) and specific heat capacity (cp), and mechanical properties, such as density (ρ) and dynamic viscosity (μ), are determined. Furthermore, combined properties like thermal diffusivity (α) and kinematic viscosity (ν), along with dimensionless parameter such as the Prandtl number (Pr), is derived. 2) In the transit mode, consistent liquid flow is maintained by controlling the pressure at the inlet and outlet. The temperature is kept constant using a feedback loop (PID control) by adjusting the heating power input (Q). This mode enables the measurement of average flow velocity (U) and convective heat transfer coefficient (h). Nusselt (Nu) number is derived from this mode, and other dimensionless parameters such as Peclet (Pe), Stanton (St), and Reynolds (Re) numbers are expressed by the integration of information from two operating modes. 3) Collectively, stationary and transit modes enable the HMRs to perform hyper-multimodal measurements, including six thermal and physical properties, four flow and device conditions, and five dimensionless numbers across various temperature levels.
[Ultrasensitive Multi-Membrane Sensors via Unconventional MEMS Fabrication]
Micromachined Ultrasonic Transducers (MUTs) play a pivotal role in a wide range of applications, including medical imaging and monitoring, non-destructive testing, and distance measurement. The two representative architectures—capacitive MUTs (CMUTs) and piezoelectric MUTs (PMUTs)—offer distinct advantages and considerable design flexibility. At MNIL, a high-temperature annealing–based process is employed to form multilayer Silicon-on-Nothing (SON) structures composed of cavity and membrane layers. This configuration provides low mechanical loss, excellent surface planarity, and high structural uniformity, enabling precise control of transducer characteristics. In particular, the multi-vacuum-layer architecture is highly suited for realizing high-Q resonators. Building on this multi-cavity SON fabrication technology, device-level implementation of multi-membrane MUTs has been achieved. Membranes arranged vertically or laterally can be mechanically and electrically coupled, allowing interaction between resonators that induces mode hybridization and resonance amplification. Such coupled-resonator architectures enable simultaneous enhancement of transmission efficiency and reception sensitivity, while also permitting controlled energy redistribution without compromising high-Q performance. These features enable bandwidth expansion or sensitivity amplification. These unconventional PMUT/CMUT architectures hold strong potential not only for sensing physical quantities such as temperature, humidity, and mass variations, but also for advanced applications including high-resolution bio-imaging, precision medical diagnostics, in vivo monitoring, and microfluidic system analysis.
Press release
MNIL은 끊임없는 도전과 혁신을 통해 새로운 과학적 지평을 열어가고 있습니다
Research
Motivation
Remember that only limited researchers have access to high-end micro-/nanofabrication facilitates worldwide.
Processes and materials we are currently relying on may not be the best out of available options.
We look for better processes for conventional micro-/nanofabrication materials and better materials
to realize high-performance transducers.
Research Interests
Large scale batch fabrication of nanostructures based on silicon self-assembly, Hydrogel based micro-/nanoelectromechanical systems, Materials and processing for flexible, stretchable, and wearable devices, Nanoscale 3D printing of organic and inorganic hybrids, 3D printing for biomedical applications, Multifunctional atomic force microscopy, Single molecule force/mass spectroscopy, High-precision Laser based manufacturing and metrology, Additive manufacturing, Heat transfer.
Current ongoing research topics
In integrated circuits (IC) and micro/nano-electromechanical systems (MEMS/NEMS), annealing is a common technique used to relieve stress in semiconductor materials, redistribute or activate dopants, heal implantation damage, and promote interfacial reactions at metal contacts. It is noteworthy that annealing can induce shape evolution or transformation in pre-structured semiconductor materials, thereby minimizing surface energy. This phenomenon enables the fabrication of distinctive semiconductor micro/nano structures through a combination of standard etching and annealing procedures. The resulting products, formed by annealing semiconductor materials at high temperatures, encompass a range of structures, including membrane-cavity and pedestal spherical structures. The aforementioned structures serve as the basis for the fabrication of high-quality semiconductor materials, functional wafers, and high-performance micro/nano devices.
[Hyper-multimodal measurements with heater-integrated microchannel resonator]
Heater-integrated microchannel resonator (HMR) is a system that integrates its key components for the first time, enabling simultaneous resonant densitometry, viscometry, and resistive thermometry. It operates in two distinct modes based on the state of the fluid sample: a stationary mode, where the liquid remains static without flow, and a transit mode, where the liquid flows through the device. 1) In the stationary mode, pressure at the channel inlet and outlet is balanced to keep the liquid static. This mode leverages the dependence of temperature response and mechanical behavior during controlled pulsed heating on the thermophysical and mechanical properties of the liquid inside the channel. By measuring temperature and mechanical resonance changes over time at high power levels, thermophysical properties, including thermal conductivity (k) and specific heat capacity (cp), and mechanical properties, such as density (ρ) and dynamic viscosity (μ), are determined. Furthermore, combined properties like thermal diffusivity (α) and kinematic viscosity (ν), along with dimensionless parameter such as the Prandtl number (Pr), is derived. 2) In the transit mode, consistent liquid flow is maintained by controlling the pressure at the inlet and outlet. The temperature is kept constant using a feedback loop (PID control) by adjusting the heating power input (Q). This mode enables the measurement of average flow velocity (U) and convective heat transfer coefficient (h). Nusselt (Nu) number is derived from this mode, and other dimensionless parameters such as Peclet (Pe), Stanton (St), and Reynolds (Re) numbers are expressed by the integration of information from two operating modes. 3) Collectively, stationary and transit modes enable the HMRs to perform hyper-multimodal measurements, including six thermal and physical properties, four flow and device conditions, and five dimensionless numbers across various temperature levels.
[Functionalized microchannel resonator for selective measurement of specific ionic targets]
Heater-integrated microchannel resonator (HMR) is a system that integrates its key components for the first time, enabling simultaneous resonant densitometry, viscometry, and resistive thermometry. It operates in two distinct modes based on the state of the fluid sample: a stationary mode, where the liquid remains static without flow, and a transit mode, where the liquid flows through the device. 1) In the stationary mode, pressure at the channel inlet and outlet is balanced to keep the liquid static. This mode leverages the dependence of temperature response and mechanical behavior during controlled pulsed heating on the thermophysical and mechanical properties of the liquid inside the channel. By measuring temperature and mechanical resonance changes over time at high power levels, thermophysical properties, including thermal conductivity (k) and specific heat capacity (cp), and mechanical properties, such as density (ρ) and dynamic viscosity (μ), are determined. Furthermore, combined properties like thermal diffusivity (α) and kinematic viscosity (ν), along with dimensionless parameter such as the Prandtl number (Pr), is derived. 2) In the transit mode, consistent liquid flow is maintained by controlling the pressure at the inlet and outlet. The temperature is kept constant using a feedback loop (PID control) by adjusting the heating power input (Q). This mode enables the measurement of average flow velocity (U) and convective heat transfer coefficient (h). Nusselt (Nu) number is derived from this mode, and other dimensionless parameters such as Peclet (Pe), Stanton (St), and Reynolds (Re) numbers are expressed by the integration of information from two operating modes. 3) Collectively, stationary and transit modes enable the HMRs to perform hyper-multimodal measurements, including six thermal and physical properties, four flow and device conditions, and five dimensionless numbers across various temperature levels.