Jeongwoo Park

Ultrasound and optical imagers are used widely in a variety of biological and medical applications. In particular, multimodal implementations combining light and sound have been actively investigated to improve imaging quality. However, the integration of optical sensors with opaque ultrasound transducers suffers from low signal-to-noise ratios, high complexity, and bulky form factors, significantly limiting its applications. Here, we demonstrate a quadruple fusion imaging system using a spheric

The difference in crystallization behavior between the as-deposited amorphous state and the melt-quenched amorphous state of Ge 2 Sb 2 Te 5 alloy has been studied using a dynamic tester. The melt-quenched amorphous alloy showed much shorter crystallization time than did the as-deposited one. We laser-annealed the as-deposited amorphous alloy under a certain condition so as to make it exhibit the same crystallization property as that of the melt-quenched one. The crystallization kinetics of this

Mobile and wearable healthcare electronics are widely used for measuring bio-signals using various fusion sensors that employ photoplethysmograms, cameras, microphones, ultrasound (US) sensors, and accelerometers. However, the consumer demand for small form factors has significantly increased as the integration of multiple sensors is difficult in small mobile or wearable devices. This study proposes two novel opto-US sensors, namely (1) a wearable photoplethysmography (PPG)-US device and (2) a P

Various processes based on atomic layer deposition (ALD) have been reported for growing Ti-based thin films such as TiN and TiO2. To improve the uniformity and conformity of thin films grown via ALD, fundamental understanding of the precursor–substrate surface reactions is required. Herein, we present a density functional theory (DFT) study of the initial nucleation process of some titanium halide precursors (TiCl4, TiBr4, and TiI4) on Si surfaces having –OH or –NH2 functional groups. We conside

Understanding the interlayer charge coupling mechanism in a two-dimensional van der Waals (vdW) heterojunction is crucial for optimizing the performance of heterostructure-based (opto)electronic devices. Here, we report mapping the gate response of a multilayer WSe₂/MoS₂ heterostructure with locally different degrees of charge depletion through mobile carrier measurements based on electrostatic force microscopy. We observed ambipolar or unipolar behavior depending on the de

Ultrasound transducers, one of the most widely used sensors in the era of the fourth Industrial Revolution, have been recognized and used in a variety of industries including medical, automotive, and robotics. In particular, recent research has focused on the development of multi-mode imaging systems that combine ultrasound and optical imaging to improve the accuracy of information acquisition. Unfortunately, its efficient combination has been severely limited due to the inherent opacity of conv

Two-dimensional electron gases (2DEGs) localized at oxide heterointerfaces can potentially be used in applications associated with the design of novel electronic device architectures. Recent studies have reported that atomic layer deposition (ALD) of Al2O3 on TiO2 substrates can generate 2DEG states, owing to in situ formation of interfacial oxygen vacancies (VO). However, the chemical mechanism governing the adsorption of the trimethylaluminum (TMA) precursor on the TiO2 surface remains unclear

Flexible printed circuit boards (FPCBs) are extensively employed as core components of modern electronic devices, including mobile and wearable devices and displays, due to their low thickness, flexibility, and low weight. However, as FPCB integration technology advances, the inner layer thickness and internal hole sizes in the FPCBs decrease, and the signal lines become finer, which increases the probability of surface and internal defect formation. We propose a nondestructive dual-modal imagin

Nano-scale fabrication of silicon substrate based on the use of atomic force microscopy (AFM) was demonstrated. A specially designed cantilever with diamond tip, allowing the formation of damaged layer on silicon substrate by a simple scratching process, has been applied instead of conventional silicon cantilever for scanning. A thin mask layer forms in the substrate at the diamond tip-sample junction along scanning path of the tip. The mask layer withstands against wet chemical etching in aqueo

Non-Destructive Testing (NDT) is vital for product safety, quality, and compliance in various industries. It enables early flaw detection, cost-effective maintenance, and customer satisfaction. NDT encompasses technologies like vision testing, radiation testing, ultrasonic testing, and magnetic testing, which are tailored to specific requirements such as environment, size, and material of the specimen. We present concurrent Photoacoustic Imaging (PAI) and Optical Coherence Tomography (OCT) for n

Multimodal optical and ultrasound imaging (USI) provides complementary diagnostic insights. However, because conventional USI uses opaque ultrasound (US) transducers, integrating these two modalities results in a bulky and complicated handheld probe in which neither modality performs efficiently. Although transparent ultrasound transducers (TUTs) solve these issues by acting as optical windows, enabling the seamless combination of light and US beams, single-element TUTs are not common in clinica

Abstract Combined photoacoustic (PA) and ultrasound (US) imaging, a promising modality for preclinical and clinical studies, can provide anatomical, physiological, and molecular information about biological tissues. However, common implementations of US imaging require an external pulser to transmit US waves, which makes integrated PA/US imaging systems relatively complicated and suboptimal. Here, without using a US pulser, simultaneous PA and laser‐induced US (LUS) imaging is demonstrated throu

We develop the optically transparent ultrasound transducer and demonstrate its applicability through integrating with photoacoustic microscopy, and optical coherence tomography. We successfully acquired dual-mode in vivo mouse images from each integrated system.