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Kim, Tae-il

Publications and source records attributed to Kim, Tae-il.

7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Temperature- and size-dependent characteristics in ultrathin inorganic light-emitting diodes assembled by transfer printing

Favorable temperature- and size-dependent device characteristics in mechanically flexible, thin (~6.45 μm thick), microscale inorganic InGaN/GaN-based light-emitting diodes enable their use as highly efficient, robust devices that are capable of integration on diverse classes of unconventional substrates, including sheets of plastic. Here, finite element analysis and systematic studies of the operational properties establish important thermal, electrical, and optical considerations for this type of device.

42 ENGINEERING↗
DOE OSTI2013

Fabrication and application of flexible, multimodal light-emitting devices for wireless optogenetics

The rise of optogenetics provides unique opportunities to advance materials and biomedical engineering, as well as fundamental understanding in neuroscience. This protocol describes the fabrication of optoelectronic devices for studying intact neural systems. Unlike optogenetic approaches that rely on rigid fiber optics tethered to external light sources, these novel devices carry wirelessly powered microscale, inorganic light-emitting diodes (μ-ILEDs) and multimodal sensors inside the brain. Here, we describe the technical procedures for construction of these devices, their corresponding radiofrequency power scavengers and their implementation in vivo for experimental application. In total, the timeline of the procedure, including device fabrication, implantation and preparation to begin in vivo experimentation, can be completed in ~3–8 weeks. Implementation of these devices allows for chronic (tested for up to 6 months) wireless optogenetic manipulation of neural circuitry in animals navigating complex natural or home-cage environments, interacting socially, and experiencing other freely moving behaviors.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2013

Deterministic assembly of releasable single crystal silicon-metal oxide field-effect devices formed from bulk wafers

Deterministic assembly of ultrathin metal oxide-semiconductor field-effect transistors released from the surfaces of bulk wafers with (111) orientation provides a route to high quality electronics on nearly any type of substrate. Device parameters and bias stability characteristics from transistors on sheets of plastic confirm the effectiveness of the approach and the critical roles of thermally grown layers of silicon dioxide for the gate dielectrics and passivation layers. Here, systematic studies of the anisotropic etching processes used to release the devices illustrate capabilities into the sub-micron thickness regime, with beneficial effects on the bending stiffness and degree of bendability.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Injectable, Cellular-Scale Optoelectronics with Applications for Wireless Optogenetics

Successful integration of advanced semiconductor devices with biological systems will accelerate basic scientific discoveries and their translation into clinical technologies. In neuroscience generally, and in optogenetics in particular, the ability to insert light sources, detectors, sensors, and other components into precise locations of the deep brain yields versatile and important capabilities. Here, we introduce an injectable class of cellular-scale optoelectronics that offers such features, with examples of unmatched operational modes in optogenetics, including completely wireless and programmed complex behavioral control over freely moving animals. Furthermore, the ability of these ultrathin, mechanically compliant, biocompatible devices to afford minimally invasive operation in the soft tissues of the mammalian brain foreshadow applications in other organ systems, with potential for broad utility in biomedical science and engineering.

42 ENGINEERING↗
DOE OSTI2013

Stretchable batteries with self-similar serpentine interconnects and integrated wireless recharging systems

An important trend in electronics involves the development of materials, mechanical designs and manufacturing strategies that enable the use of unconventional substrates, such as polymer films, metal foils, paper sheets or rubber slabs. The last possibility is particularly challenging because the systems must accommodate not only bending but also stretching. Although several approaches are available for the electronics, a persistent difficulty is in power supplies that have similar mechanical properties, to allow their co-integration with the electronics. In this study we introduce a set of materials and design concepts for a rechargeable lithium ion battery technology that exploits thin, low modulus silicone elastomers as substrates, with a segmented design in the active materials, and unusual ‘self-similar’ interconnect structures between them. The result enables reversible levels of stretchability up to 300%, while maintaining capacity densities of ~1.1 mAh cm ⁻2 . Stretchable wireless power transmission systems provide the means to charge these types of batteries, without direct physical contact.

25 ENERGY STORAGE↗
DOE OSTI2011

Epidermal Electronics

We report classes of electronic systems that achieve thicknesses, effective elastic moduli, bending stiffnesses, and areal mass densities matched to the epidermis. Unlike traditional wafer-based technologies, laminating such devices onto the skin leads to conformal contact and adequate adhesion based on van der Waals interactions alone, in a manner that is mechanically invisible to the user. We describe systems incorporating electrophysiological, temperature, and strain sensors, as well as transistors, light-emitting diodes, photodetectors, radio frequency inductors, capacitors, oscillators, and rectifying diodes. Solar cells and wireless coils provide options for power supply. Furthermore, we used this type of technology to measure electrical activity produced by the heart, brain, and skeletal muscles and show that the resulting data contain sufficient information for an unusual type of computer game controller.

42 ENGINEERING↗