Min-joon Park

Multifunctional wearable devices for diagnosis and therapy of movement disorders

Wearable systems that monitor muscle activity, store data and deliver feedback therapy are the next frontier in personalized medicine and healthcare. However, technical challenges, such as the fabrication of high-performance, energy-efficient sensors and memory modules that are in intimate mechanical contact with soft tissues, in conjunction with controlled delivery of therapeutic agents, limit the wide-scale adoption of such systems. Here, we describe materials, mechanics and designs for multifunctional, wearable-on-the-skin systems that address these challenges via monolithic integration of nanomembranes fabricated with a top-down approach, nanoparticles assembled by bottom-up methods, and stretchable electronics on a tissue-like polymeric substrate. Representative examples of such systems include physiological sensors, non-volatile memory and drug-release actuators. Quantitative analyses of the electronics, mechanics, heat-transfer and drug-diffusion characteristics validate the operation of individual components, thereby enabling system-level multifunctionalities.

Stretchable Carbon Nanotube Charge-Trap Floating-Gate Memory and Logic Devices for Wearable Electronics

Electronics for wearable applications require soft, flexible, and stretchable materials and designs to overcome the mechanical mismatch between the human body and devices. A key requirement for such wearable electronics is reliable operation with high performance and robustness during various deformations induced by motions. Here, we present materials and device design strategies for the core elements of wearable electronics, such as transistors, charge-trap floating-gate memory units, and various logic gates, with stretchable form factors. The use of semiconducting carbon nanotube networks designed for integration with charge traps and ultrathin dielectric layers meets the performance requirements as well as reliability, proven by detailed material and electrical characterizations using statistics. Serpentine interconnections and neutral mechanical plane layouts further enhance the deformability required for skin-based systems. Repetitive stretching tests and studies in mechanics corroborate the validity of the current approaches.

Oxide nanomembrane hybrids with enhanced mechano- and thermo-sensitivity for semitransparent epidermal electronics.

Oxide nanomembrane hybrids with enhanced mechano- and thermo-sensitivity for semitransparent epidermal electronics are developed. The use of nanomaterials (single wall nanotubes and silver nanoparticles) embedded in the oxide nanomembranes significantly enhances mechanical and thermal sensitivities. These mechanical and thermal sensors are utilized in wheelchair control and hypothermia detection, which are useful for patients with strokes.

Single pass acceleration experiment using coaxial cavity

The high power electron accelerator (FANTRON-I) for industrial applications is under development at Physico-technology laboratory, KAPRA (Korea Accelerator and Plasma Research Association). To validate the acceleration scheme, single pass acceleration experimental setup using nonagon shape coaxial cavity has been installed. The experimental setup consists of an electron gun, coaxial cavity, bending magnet, beam diagnostic and dump chamber, RF amplifier, vacuum and cooling system. A Rogowiski type gun with Th-W wire filament was used as an electron gun and produced 20 kV, 0.8 mA electron beam. A 159.41 MHz, 3 kW RF system consists of an oscillator, 100 W solid state amplifier and 3 kW tetrode amplifier. The bending magnet composed of main and supplementary magnet for weak focusing was designed, fabricated and tested. In this paper, the test results of the acceleration system components using nonagon shape coaxial cavity are analyzed and the design status of FANTRON-I are presented.

Design, study on the rf source for KOMAC

A study on the design of 700 MHz, 1 MW CW klystron amplifier for KOMAC (KOrea Multipurpose Accelerator Complex) proton accelerator has been carried out by KAPRA (Korea Accelerator and Plasma Research Association). A triode type electron gun including a modulating anode, six cavities including one second harmonic cavity and electromagnet for electron beam focusing were designed to produce desired output rf power. Thermal analysis at the collector according to the magnetic field profile near the collector side pole face was performed to efficiently cool the heat generated through the kinetic energy loss of the electron beam. In addition to the design study, an operation experiment of the klystron for broadcasting whose output power was 15 kW and frequency range 574 - 698 MHz was performed at 700 MHz. In this paper, the results of the design study and the operation experiment of the klystron for broadcasting at 700 MHz are presented.

High performance bio-integrated devices

In recent years, personalized electronics for medical applications, particularly, have attracted much attention with the rise of smartphones because the coupling of such devices and smartphones enables the continuous health-monitoring in patients’ daily life. Especially, it is expected that the high performance biomedical electronics integrated with the human body can open new opportunities in the ubiquitous healthcare. However, the mechanical and geometrical constraints inherent in all standard forms of high performance rigid wafer-based electronics raise unique integration challenges with biotic entities. Here, we describe materials and design constructs for high performance skin-mountable bio-integrated electronic devices, which incorporate arrays of single crystalline inorganic nanomembranes. The resulting electronic devices include flexible and stretchable electrophysiology electrodes and sensors coupled with active electronic components. These advances in bio-integrated systems create new directions in the personalized health monitoring and/or human-machine interfaces.

Development of a compact Helicon ion source for a neutron generator

Summary form only given, as follows. Summary form only given. A compact Helicon ion source has been developed for a neutron generator, which makes use of D-D nuclear fusion reaction on the copper based Ti target bombarded with an energetic deuterium beam. For high neutron yield, high-current ion beams need to be extracted from high-density plasma sources such as a helicon plasma source known for its high efficiency of generating high-density plasmas. Plasma densities of 10/sup 12/ cm/sup -3/ are obtained with 2 kW RF power at the frequency of 13.56 MHz. Permanent magnets are installed to provide sufficient axial magnetic fields for the helicon mode operation. Langmuir probes and optical emission spectroscopy are used to examine plasma characteristics such as plasma density and electron temperature for the optimization of high-current ion beam extraction. Ion beam currents of a few tens of mA have been extracted at the extraction voltage of 30kV.

Design and construction of a compact neutron generator using an RF ion source

Summary form only given, as follows. A compact neutron generator of which the diameter is 4 has been designed and constructed for various applications. The generation of neutron in this device is based on the D-D fusion reactions in the target, producing 2.5 MeV neutrons.