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

• Introduction slides (Prof. Lee)
• Introduction slides (Ongoing research)

Current ongoing research topics

1. Manufacturing & Fabrication

• 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.

2. Sensing & Instrumentation

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 (c_p), 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 microchannels for selective measurement of a specific ionic targets

Press releases

• Nanoscale topographic information from optical microscope and AI learning
• NIR Interferometric microscope
• Pulled microtube resonators
• Hydrogel AFM cantilevers
• Cell mass measurements
• Soft AFM cantilevers via dynamic mask lithography
• Phase change mediated transfer of stretched liquid metal patterns