Korea Advanced Institute of Science and Technology · Engineering
Professor Hyunjoo J. Lee's research lab specializes in the development of advanced micro- and nanoscale sensors for biomedical and environmental applications. The lab focuses on creating highly sensitive, miniaturized resonant sensors—particularly capacitive micromachined ultrasonic transducers (CMUTs)—for real-time detection of gases, vapors, and biomolecules at ultra-trace levels. Key research directions include the integration of mesoporous materials and biocompatible adhesives (e.g., calcium-modified silk fibroin) to enhance sensor performance and biointerfacing, as well as the design of implantable and wearable neuromodulation systems using focused ultrasound. The lab also emphasizes system-level integration, including low-power CMOS circuits and noise-reduction techniques, to enable practical deployment in consumer, defense, and clinical settings.
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Abstract With the increasing interest and demand for epidermal electronics, a strong interface between a sensor and a biological surface is essential, yet achieving such interface is still a challenge. Here, a calcium (Ca)‐modified biocompatible silk fibroin as a strong adhesive for epidermal electronics is proposed and the physical principles behind its interfacial and adhesive properties are reported. A strong adhesive characteristic (>800 N m −1 ) is observed because of the increase in bot
Distributed sensing of gas-phase chemicals using highly sensitive and inexpensive sensors is of great interest for many defense and consumer applications. In this paper we present ppb-level detection of dimethyl methylphosphonate (DMMP), a common simulant for sarin gas, with a ppt-level resolution using an improved capacitive micromachined ultrasonic transducer (CMUT) as a resonant chemical sensor. The improved CMUT operates at a higher resonant frequency of 47.7 MHz and offers an improved mass
Distributed sensing of gas-phase chemicals is a promising application for mesoporous materials when combined with highly sensitive miniaturized gas sensors. We present a direct application of a mesoporous silica thin film on a highly sensitive miniaturized resonant chemical sensor with a mass sensitivity at the zeptogram scale for relative humidity and CO(2) detection. Using mesoporous silica thin-film, we report one of the lowest volume resolutions and a sensitive detection of 5.1 × 10(-4)% RH/
Developed over approximately half a century, neural probe technology is now a mature technology in terms of its fabrication technology and serves as a practical alternative to the traditional microwires for extracellular recording. Through extensive exploration of fabrication methods, structural shapes, materials, and stimulation functionalities, neural probes are now denser, more functional and reliable. Thus, applications of neural probes are not limited to extracellular recording, brain-machi
Transcranial focused ultrasound stimulation is a promising therapeutic modality for human brain disorders because of its noninvasiveness, long penetration depth, and versatile spatial control capability through beamforming and beam steering. However, the skull presents a major hurdle for successful applications of ultrasound stimulation. Specifically, skull-induced focal aberration limits the capability for accurate and versatile targeting of brain subregions. In addition, there lacks a fully fu
Vapor detection using highly sensitive miniaturized resonant sensors is of great interest for many applications, including consumer, industrial, and environmental applications. An operational-amplifier-based multichannel oscillator that interfaces with a 50-MHz capacitive micromachined ultrasonic transducer array is presented for chemical sensing applications. The circuit was implemented in a 0.18-μm CMOS technology to reduce power consumption, number of wires, and active area per channel. The p
Abstract Development of polymeric memristors is of great interest for wearable and implantable applications because of its flexibility and transparency. One of distinguished polymeric memristor materials is silk fibroin, which is a biodegradable protein extracted from Bombyx mori cocoons. However, fibroin memristors demonstrated earlier show low memory cell density (<100 cells mm −2 ). In this paper, silk fibroin memristors with cell density 25 times higher than that of the previously reporte
We present an 18-MHz capacitive micromachined ultrasonic transducer (CMUT), used as a chemical sensor for detection of a common simulant for chemical weapons, dimethyl methylphosphonate (DMMP), in air. CMUTs are attractive for chemical sensor applications because of their unprecedented mass sensitivity per membrane area, low motional impedance, and high quality factor compared to other flexural-mode resonators. The device is composed of 1000 individual cells operating in parallel, which provides
The development of portable volatile organic compound (VOC) sensors is essential for home healthcare and workplace safety because VOCs are environmental pollutants that may critically affect human health. Here, we report a compact and portable sensor platform based on a capacitive micromachined ultrasonic transducer (CMUT) array offering multiplex detection of various VOCs (toluene, acetone, ethanol, and methanol) using a single read-out system. Three CMUT resonant devices were functionalized wi
Though many studies have been published about therapeutic potentials of selective 5-HT<sub>7</sub>R ligands, there have been few biased ligands of 5-HT<sub>7</sub>R. The development of potent and selective biased ligands of 5-HT<sub>7</sub>R would be of great help in understanding the relationship between pharmacological effects and G protein/β-arrestin signaling pathways of 5-HT<sub>7</sub>R. In order to identify 5-HT<sub>7</sub>R ligands with biased agonism, we designed and synthesized a serie
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