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Hexagonal metal complex based mechanically robust transparent ultrathin gold μECoG for electro-optical neural interfaces

2025-03-31T15:00:00Z

Title: Hexagonal metal complex based mechanically robust transparent ultrathin gold μECoG for electro-optical neural interfaces Author(s): Kim, Duhee; Bissannagari, Murali; Kim, Boil; Hong, Nari; Park, Jaeu; Lim, Hyeongtae; Lee, Junhee; Lee, Jungha; Kim, Yoon Kyoung; Cho, Youngjae; Lee, Kwang; Lee, Junghyup; Yoon, Jong-Hyeok; Jang, Jae Eun; Tsai, David; Lee, Sanghoon; Kwon, Hyuk-Jun; Choe, Han Kyoung; Kang, Hongki Abstract: Transparent electro-optical neural interfacing technologies offer simultaneous high-spatial-resolution microscopic imaging, and high-temporal-resolution electrical recording and stimulation. However, fabricating transparent, flexible, and mechanically robust neural electrodes with high electrochemical performance remains challenging. In this study, we fabricated transparent (72.7% at 570 nm), mechanically robust (0.05% resistance change after 50k bending cycles) ultrathin Au microelectrodes for micro-electrocorticography (mu ECoG) using a hexadentate metal-polymer ligand bonding with an EDTA/PSS seed layer. These transparent mu ECoG arrays, fabricated with biocompatible gold, exhibit excellent electrochemical properties (0.73 Omegacm2) for neural recording and stimulation with long-term stability. We recorded brain surface waves in vivo, maintaining a low baseline noise and a high signal-to-noise ratio during acute and two-week recordings. In addition, we successfully performed optogenetic modulation without light-induced artifacts at 7.32 mW/mm2 laser power density. This approach shows great potential for scalable, implantable neural electrodes and wearable optoelectronic devices in digital healthcare systems.

Transparent Temperature Sensors for Photothermal Neuromodulation: Advances, Challenges, and Future Directions

2025-06-30T15:00:00Z

Title: Transparent Temperature Sensors for Photothermal Neuromodulation: Advances, Challenges, and Future Directions Author(s): Lee, Jee Woong; Lee, Junhee; Lee, Jungha; Kim, Duhee; Hong, Woongki; Lee, Junghyup; Song, Minyoung; Kang, Hongki Abstract: Photothermal neuromodulation, a rapidly advancing technique in neuroscience, has been introduced as an incredibly versatile platform for the in-depth study of neural electrophysiological signals and the development of treatments for various neurological disorders. Particularly, nanomaterial-based photothermal neuromodulation technologies have advantages compared to optogenetic stimulation methods, such as non-genetic modification, minimally invasive, and reduced immune response. Photothermal neuromodulation research has introduced various nanomaterials and stimulation methods to regulate thermosensitive ion channels or modify cell membrane capacitance, enabling excitation and inhibition of neural activity. Recent advances in nanomaterials have significantly improved the precision and efficiency of photothermal neuromodulation, expanding its potential applications in neuroscience research. In the photothermal neuromodulation studies, different temperature measurement methods have been used but do not satisfy all the requirements necessary to analyze this phenomenon. An ideal temperature sensor for a photothermal neuromodulation study must have high transparency, high thermal sensitivity, and high spatial and temporal resolution. This review aims to cover the current status of thermally induced neuromodulation studies and the transparent temperature sensing methodologies that can be used for photothermal neuromodulation.

Wireless System Miniaturization Solutions for Ingestible Sensors

2024-11-30T15:00:00Z

Title: Wireless System Miniaturization Solutions for Ingestible Sensors Author(s): Kim, Chanyoung; Lee, Junghyup; Song, Minyoung Abstract: Ingestible sensors are pivotal in monitoring the gastrointestinal (GI) tract and enhancing comprehension of complex gastrointestinal processes, propelled by sensor technology advancements. They must ensure robust wireless communication from deep within the body while maintaining longevity for comprehensive monitoring. Wireless system miniaturization stands as a promising solution to these challenges. This paper introduces the current state and technical challenges ingestible sensors and their solutions for wireless system miniaturization. The key techniques for further miniaturization include the antenna miniaturization, integration of adaptive impedance matching networks, and the replacement of crystal. Additionally, the paper explores future directions for wireless communication systems to support the continued advancement of ingestible sensor technology.

A PVT-Insensitive Sub-Ranging Current Reference Achieving 11.4-ppm° C From-20° C to 125 ° C

2024-11-30T15:00:00Z

Title: A PVT-Insensitive Sub-Ranging Current Reference Achieving 11.4-ppm° C From-20° C to 125 ° C Author(s): Park, Pangi; Lee, Junghyup; Cho, Seonghwan Abstract: This article presents a sub-ranging current reference with a low-temperature coefficient (TC) across a wide temperature range. By using a TC-adjustable current source and a process-insensitive sub-range detector, the impact of second-order TC can be reduced by nearly fourfold, without any discontinuities at the subrange boundaries. Implemented in a 0.18-μ m CMOS process, the proposed current reference achieves an average TC of 11.4-ppm/°C across from -20 °C to 125 °C, obtained from 45 samples across five process corners without chip-by-chip calibration. The proposed current source exhibits low line and load sensitivities of 365 and 181 ppm/V, respectively, and an integrated noise of 38.9 pArms within a 10-Hz bandwidth. © 2024 IEEE.