Byung Chul Lee

Faradaic electrochemical impedance spectroscopy (f-EIS) in the presence of redox reagent, e.g., [Fe(CN)6]3−/4−, is widely used in biosensors owing to its high sensitivity. However, in sensors detecting amyloid beta (Aβ), the redox reagent can cause the aggregation of Aβ, which is a disturbance factor in accurate detection. Here, we propose an interdigitated microelectrode (IME) based f-EIS technique that can alleviate the aggregation of Aβ and achieve high sensitivity by buffer control. The prop

Capacitive micromachined ultrasonic transducers (CMUTs) with substrate-embedded springs offer highly efficient output pressure performance over conventional CMUTs, owing to their nonflexural parallel plate movement. The embedded silicon springs support thick Si piston plates, creating a large nonflexural average volume displacement efficiency in the operating frequency range from 1⁻3 MHz. Static and dynamic volume displacements of the nonflexural parallel plates were examined using white light i

Due to its additional frequency response, dual-frequency ultrasound has advantages over conventional ultrasound, which operates at a specific frequency band. Moreover, a tunable frequency from a single transducer enables sonographers to achieve ultrasound images with a large detection area and high resolution. This facilitates the availability of more advanced techniques that simultaneously require low- and high-frequency ultrasounds, such as harmonic imaging and image-guided therapy. In this st

This study aims at creating low-cost, three-dimensional (3D), freehand ultrasound image reconstructions from commercial two-dimensional (2D) probes. The low-cost system that can be attached to a commercial 2D ultrasound probe consists of commercial ultrasonic distance sensors, a gimbal, and an inertial measurement unit (IMU). To calibrate irregular movements of the probe during scanning, relative position data were collected from the ultrasonic sensors that were attached to a gimbal. The directi

Resonant tunneling metalenses have excellent applications for subwavelength ultrasonic imaging in air. In this study, an acoustic metalens intended for underwater imaging was designed with first, second, and third resonant tunneling frequencies of 10.3, 85.3, and 105.9 kHz, respectively. The resonant tunneling metalens and letter-shaped validation specimens were fabricated via additive manufacturing using polymers. Before the underwater experiment, an array of 36 channels of lead zirconate titan

A capacitive micromachined ultrasonic transducer (CMUT) with substrate-embedded springs, as named post-CMUT or PCMUT, provides many benefits over a conventional CMUT having flexural plate movement. Since the PCMUT structure resembles an ideal piston transducer, the improvements in performance mainly stem from the higher average displacement of the top plate for a given gap height. In this work, comprehensive 3-D finite element analysis (FEA) models are developed to further our understanding of t

Rhododendron brachycarpum is a evergreen broad-leaved shrub and belongs to the Ericaceae family and the Rhododendron genus. It is well known for its beautiful leaves and flowers. There are 11 species of the Rhododendron genus in Korea. It includes 3 species - Rhododendron brachycarpum, Rhododendron aureum Georgi and Rhododendron brachycarpum var. roseum Koidz. They grow naturally over 1,000 meters above sea level of the Baekdu Mountain Range in Korea. These habitats, according to investigations

This article presents a relaxor ferroelectric, lead magnesium niobate-lead zirconate titanate (PMN-PZT)-thin-film-based piezoelectric drop-on-demand printhead exhibiting high jetting capability and thermal stability. Unlike conventional piezoelectric materials such as lead zirconate titanate (PZT), the PMN-PZT film demonstrates high electrical responsiveness to polarization and reduced hysteresis loss due to polar nano regions, thereby improving printhead’s performance. Our research involves a c

A microfabricated neural thermocouple arrays probe (NTAP) is proposed for measuring and comparing the temperature of local brain area in real time sensing. Four junctions of T type thin film thermocouple arrays were fabricated on a sharp silicon probe tip. Each junction size was 20 mum by 20 mum. The average seebeck coefficient was 15.12 muV/ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> C and the dynamic response time was 0.78 sec. The te

Target-specific drug release is indispensable to improve chemotherapeutic efficacy as it enhances drug uptake and penetration into tumors. Sono-responsive drug-loaded nano-/micro-particles are a promising solution for achieving target specificity by exposing them to ultrasound near tumors. However, the complicated synthetic processes and limited ultrasound (US) exposure conditions, such as limited control of ultrasound focal depth and acoustic power, prevent the practical application of this app

In this paper, we introduce a modified fabrication method for CMUTs with substrate-embedded springs (post-CMUTs or PCMUTs) to increase the fabrication yield. This modified fabrication process includes three additional steps from the previous process: vacuum cleaning prior to the wafer bonding step, thermal oxidation of the silicon piston top plate, and preservation of the 150-nm buried oxide (BOX) layer on top of the 250 nm Si layer of the bonded SOI wafer. These modifications increased the fabr