Jungchul Lee

Silicon atomic force microscope (AFM) cantilevers having integrated solid-state heaters were originally developed for application to data storage, but have since been applied to metrology, thermophysical property measurements, and nanoscale manufacturing. These applications beyond data storage have strict requirements for mechanical characterization and precise temperature calibration of the cantilever. This paper describes detailed mechanical, electrical, and thermal characterization and calibr

Using suspended nanochannel resonators (SNRs), we demonstrate measurements of mass in solution with a resolution of 27 ag in a 1 kHz bandwidth, which represents a 100-fold improvement over existing suspended microchannel resonators and, to our knowledge, is the most precise mass measurement in liquid today. The SNR consists of a cantilever that is 50 microm long, 10 microm wide, and 1.3 microm thick, with an embedded nanochannel that is 2 microm wide and 700 nm tall. The SNR has a resonance freq

The vapour?liquid?solid (VLS) growth of TiO2 nanowires (NWs) was performed using a thermally evaporated Ti source and sputter-deposited Au?catalysts under an O2 gas flow. High-density single-crystalline TiO2 NWs having the rutile structure were successfully grown on sapphire (single-crystal ?-Al2O3) and quartz (amorphous SiO2) substrates. Ti buffer layers, deposited on the substrates to prevent undesirable reactions between the Ti vapour and substrates, were identified to promote the TiO2 NW gro

Synthesis of TiO 2 nanowires directly on conductive and transparent glass substrates would be very useful for various applications such as photovoltaics and photocatalysis. Here, we report for the first time that single-crystalline TiO 2 nanowires can be synthesized on fluorine-doped tin oxide (SnO 2:F)-coated soda-lime glass substrates by chemical vapor deposition (CVD) at a temperature that is below the glass softening temperature (<530 °C). Moreover, we demonstrate that CdS nanorods with high

Polydimethylsiloxane (PDMS) is a prominent material for radiative cooling due to its promising optical properties in the mid-infrared spectral region as well as its fabrication easiness. Even though several works have reported that the mid-infrared emissivity of a PDMS film can be increased by surface modification, there is still room for further enhancement through global optimization. Here, we designed and fabricated the thin PDMS film patterned with two-dimensional gratings to obtain the high

Precision frequency detection has enabled the suspended microchannel resonator (SMR) to weigh single living cells, single nanoparticles, and adsorbed protein layers in fluid. To date, the SMR resonance frequency has been determined optically, which requires the use of an external laser and photodiode and cannot be easily arrayed for multiplexed measurements. Here we demonstrate the first electronic detection of SMR resonance frequency by fabricating piezoresistive sensors using ion implantation

Liquid metals are one of the most interesting and promising materials due to their electrical, fluidic, and thermophysical properties. With the aid of their exceptional deformable natures, liquid metals are now considered to be electrically conductive materials for sensors and actuators, major constituent transducers in soft robotics, that can experience and withstand significant levels of mechanical deformation. For the upcoming era of wearable electronics and soft robotics, we would like to of

This paper reports the thermal and electrical characteristics of a heated microcantilever in air and helium over a wide range of pressures. The cantilever heater size modulates thermal conductance between the cantilever and its gaseous surroundings; and the Knudsen number, Kn characterizes this thermal conductance. When Kn&amp;lt;1, thermal transport from the cantilever heater depends on gas pressure, and when Kn&amp;gt;1, thermal transport from the cantilever heater remains constant. This measu

Abstract A novel direct writing of eutectic gallium indium (EGaIn) patterns on uneven surfaces including both inclined and curved substrates is reported. The approach relies on four degrees‐of‐freedom motion control of the pressurized EGaIn dispenser and precise sensing of the dispenser tip–substrate distance. An experimental hardware is built by using three motorized linear stages, a motorized rotation stage, two electronic pressure regulators, and a laser distance sensor and operating programs

Since the invention of the atomic force microscope (AFM) three decades ago, there have been numerous advances in its measurement capabilities. Curiously, throughout these developments, the fundamental nature of the force-sensing probe-the key actuating element-has remained largely unchanged. It is produced by long-established microfabrication etching strategies and typically composed of silicon-based materials. Here, we report a new class of photopolymerizable hydrogel nano-probes that are produ

Abstract Eutectic gallium indium (EGaIn) is actively investigated toward wearable and stretchable electronic devices due to the high fluidity, high electrical conductivity, and low toxicity. However, high surface tension along with spontaneous oxidation makes fine patterning below ≈10 µm challenging. In this paper, a novel manufacturing technique that enables EGaIn patterns of single‐digit micrometer widths on planar elastomeric substrates is presented. First, a custom direct printing setup is c

High-density single-crystalline TiO 2 nanowires (∼50 nm diam) were successfully grown on Ti substrates by chemical vapor deposition at a low temperature of 700 °C and within a remarkably short time period of 5 min. They were combined with CdSe nanocrystals (∼5 nm diam) to form TiO 2 /CdSe heterotructured nanowires by overcoating the nanowires with the CdSe-containing solution and subsequent annealing at 600 °C. The TiO 2 /CdSe nanowires showed uniformly distributed CdSe nanocrystals, and high cr