Yeonsik Choi

Bioresorbable electronic stimulators are of rapidly growing interest as unusual therapeutic platforms, i.e., bioelectronic medicines, for treating disease states, accelerating wound healing processes and eliminating infections. Here, we present advanced materials that support operation in these systems over clinically relevant timeframes, ultimately bioresorbing harmlessly to benign products without residues, to eliminate the need for surgical extraction. Our findings overcome key challenges of

Temporary postoperative cardiac pacing requires devices with percutaneous leads and external wired power and control systems. This hardware introduces risks for infection, limitations on patient mobility, and requirements for surgical extraction procedures. Bioresorbable pacemakers mitigate some of these disadvantages, but they demand pairing with external, wired systems and secondary mechanisms for control. We present a transient closed-loop system that combines a time-synchronized, wireless ne

Implantable drug release platforms that offer wirelessly programmable control over pharmacokinetics have potential in advanced treatment protocols for hormone imbalances, malignant cancers, diabetic conditions, and others. We present a system with this type of functionality in which the constituent materials undergo complete bioresorption to eliminate device load from the patient after completing the final stage of the release process. Here, bioresorbable polyanhydride reservoirs store drugs in

Abstract Since 2012, triboelectric energy harvesting technologies have received a substantial amount of attention as they constitute one of the most efficient ways of transforming vibrational and frictional energy into electrical energy, regardless of location and environmental conditions. One of the most significant advantages of this technology is in the suitability of a very wide range of materials that can be readily incorporated into devices. In order to achieve efficient energy harvesting

Highly crystalline and “self-poled” δ′-phase Nylon-11 nanowires, fabricated using a novel gas-flow assisted nano-template infiltration method, exhibit enhanced triboelectric energy harvesting performance.

Abstract Bioresorbable electronic systems represent an emerging class of technology of interest due to their ability to dissolve, chemically degrade, disintegrate, and/or otherwise physically disappear harmlessly in biological environments, as the basis for temporary implants that avoid the need for secondary surgical extraction procedures. Polyanhydride‐based polymers can serve as hydrophobic encapsulation layers for such systems, as a subset of the broader field of transient electronics, where

Dipole alignment in ferroelectric polymers is routinely exploited for applications in charge-based applications. Here, we present the first experimental realization of ideally ordered dipole alignment in α-phase nylon-11 nanowires. This is an unprecedented discovery as dipole alignment is typically only ever achieved in ferroelectric polymers using an applied electric field, whereas here, we achieve dipole alignment in as-fabricated nanowires of 'non-ferroelectric' α-phase nylon-11, an overlooke

Abstract Triboelectric energy harvesting from ambient mechanical sources relies on motion‐generated surface charge transfer between materials with different electron affinities. In order to achieve highly efficient energy harvesting performance, choosing materials with a high surface charge density is crucial, and odd‐numbered polyamides (Nylons), such as Nylon‐11, are particularly promising due to their strong electron‐donating characteristics and the possibility to achieve dipolar alignment le

Lithium (Li) metal is a promising anode material for high-energy-density Li batteries due to its high specific capacity. However, the uneven deposition of Li metal causes significant volume expansion and safety concerns. Here, we investigate the impact of a gradient-infused Li-metal anode using silver (Ag)-decorated carbonized cellulose fibers (Ag@CC) as a three-dimensional (3D) current collector. The loading level of the gradient-infused Li-metal anode is controlled by the thermal infusion time

Crystal structure is crucial in determining the properties of piezoelectric polymers, particularly at the nanoscale where precise control of the crystalline phase is possible. Here, we investigate the electromechanical properties of three distinct crystalline phases of Nylon-11 nanowires using advanced scanning probe microscopy techniques. Stiff α-phase nanowires exhibited a low piezoelectric response, while relatively soft δ'-phase nanowires displayed an enhanced piezoelectric response.

Abstract Films made of 2D networks of single‐walled carbon nanotubes (SWNTs) are one of the most promising active‐channel materials for field‐effect transistors (FETs) and have a variety of flexible electronic applications, ranging from biological and chemical sensors to high‐speed switching devices. Challenges, however, still remain due to the current hysteresis of SWNT‐containing FETs, which has hindered further development. A new and robust method to control the current hysteresis of a SWNT‐n

In the arena of materials science, the landscape of implantable sensors and stimulators is rapidly advancing, taking the form of transient electronics or what is colloquially known as "bioresorbable electronic medicine." This pioneering technology holds a distinct advantage, as it dissolves within the human body, obviating the necessity for permanent implants and the attendant risks associated with removal surgeries. In the quest to fabricate bioresorbable devices with enduring in vivo stability

이 글은 조선 초기 정치이념의 전환과정에 내재되어 있었던 신유학과 불교 사이의 이념적 긴장을 분석하는 데 목적이 있다. 이 주제에 관한 기존의 연구들은 한편으로는 성리학자들이 제시했던 정통과 이단을 구분하는 기준이 세속성의 문제였다는 점을 간과했고, 다른 한편으로는 불교가 세속의 종교임을 항변했던 호교론의 의미를 포착하지 못했다. 따라서 조선 초기의 유불논쟁을 객관적으로 분석하기 위해서는 양자간에 쟁점이 되었던 논쟁의 접점을 중심으로 한 비교연구가 필요하다. 정도전을 비롯한 조선 초기 성리학자들의 척불론을 촉발시킨 것은 불교교단의 세속적 타락이었다. 따라서 불교계는 어떠한 형태로든 이 문제에 답변해야 했다. 그러나 교단의 지도자 기화(己和, 1376-1433)는 불교교단이 안고 있었던 현실적 문제점들을 외면했다. 단지 그는 보유론의 관점에서 불교와 유학의 화해를 모색했다. 그는 출세간을 지향하는 종교가 왜 세속의 문제에 개입해야 하는지, 그리고 종교의 세속개입이 초래한 교단의 병리를