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In Kenya, the ‘Linda Mama Program’, a free care program for pregnant women, is being implemented, but as of 2017, maternal deaths per 100,000 live births reached 342, and the infection rate such as AIDS, hepatitis B, and syphilis is high. Diagnosis is being made centering on a quick simple test (rapid diagnosis), but the reliability is low, so an accurate and quick diagnosis method is needed. Through the Innovative Technology Program (CTS) of Korea International Cooperation Agency (KOICA), we developed a multi-immune diagnostic device and multi-diagnostic kit that can diagnose AIDS, hepatitis B, and syphilis, which can be tested with minimal education at schools and local public health centers in addition to hospitals. The sensitivity and specificity of the diagnostic kit were each 90% or more, which was improved by more than 20% compared to the rapid diagnostic kits. The supply of cost-competitive diagnostic devices and test kits will enable continuous monitoring of AIDS, hepatitis B, and syphilis infections among women of childbearing age between the ages of 15 and 49, thereby contributing to the improvement of maternal and child health.

In this paper we report the results on the optimization of the bi-layer lift-off resist (LOR) SiO2 sputter-deposition technique which is ideal for obtaining damage-free multi-electrode array (MEA). To optimize the bi-layer overhang formation, we have examined the undercut formation kinetics of LOR bottom layer and the dependence of the SiO2 sputter-deposition lift-off processed electrode structure on the undercut length. Crater-shaped and recessed electrode structure is obtained when the undercut length is short (≤2 μm) and longer than 3 μm, respectively. To optimize the SiO2 sputter-deposition process, we have examined the dependence of Au electrode passivation on the SiO2 sputtering parameters in terms of electrochemical cyclic-voltammogram (CV), impedance, electrical noise, sputter-deposition rate and in vitro neuronal activity recording property. The MEAs passivated under pure argon supply condition showed poor barrier properties, poor neuronal signal recording performance, and cytotoxic property. The CV of MEAs passivated under oxygen mixing ratios above 5% showed traditional sigmoidal CV and long-term recording of neuronal activities, probing the excellent barrier property and cytocompatibility of the SiO2 films sputter-deposited under oxygen mixing conditions. We have also issued thermal damaging aspect of bi-layer overhang structure which is tightly coupled with the detailed electrode structure and the high sputter-deposition rate. Finally, it was suggested that measurement of CV, electrochemical impedance and electrical noise can be a viable tool in evaluating the barrier performance of a passivation layer.

A high-efficiency voltage regulation stage in an energy harvesting system is presented. In an energy harvesting system, the availability of energy is uncertain. If energy is harvested from energy resources, the system operates; if not, the system does not work. Therefore, the energy harvesting system starts and stops repeatedly according to the presence or absence of energy. The repeated on and off state in the energy harvesting system decreases operating efficiency which is an important factor in such a system with the limited amount of harvested energy. To improve the efficiency of the system that repeatedly switch between on and off states, the energy dissipated in the transitional state should be minimized. In this work, a voltage regulation stage is implemented with two additional switches, two low power comparators and digital control logic in addition to the conventional regulation stage. The first switch determines the input voltage level of the regulation stage, and the second switch prevents undesired energy dissipation in the boosting state. When the regulation stage supplies power to a 100 ohm load resistor with a 100 uF load capacitor for 50 ms, the efficiency is improved up to 38%, and boosting time is reduced by 42% in comparison with the conventional regulation structure.

Objective. Nanoporous gold (Au) structures can reduce the impedance and enhance the charge injection capability of multi-electrode arrays (MEAs) used for interfacing neuronal networks. Even though there are various nanoporous Au preparation techniques, fabrication of MEA based on low-cost electro-codeposition of Ag:Au has not been performed. In this work, we have modified a Au MEA via the electro-codeposition of Ag:Au alloy, followed by the chemical etching of Ag, and report on the in vitro extracellular recording and stimulation performance of the nanoporous Au-modified MEA. Approach. Ag:Au alloy was electro-codeposited on a bilayer lift-off resist sputter-deposition passivated Au MEA followed by chemical etching of Ag to form a porous Au structure. Main results. The porous Au structure was analyzed by scanning electron microscopy and tunneling electron microscopy and found to have an interconnected nanoporous Au structure. The impedance value of the nanoporous Au-modified MEA is 15.4 ± 0.55 kΩ at 1 kHz, accompanied by the base noise V rms of 2.4 ± 0.3 μV. The charge injection limit of the nanoporous Au-modified electrode estimated from voltage transient measurement is approximately 1 mC cm−2, which is comparable to roughened platinum and carbon nanotube electrodes. The charge injection capability of the nanoporous Au-modified MEA was confirmed by observing stimulus-induced spikes at above 0.2 V. The nanoporous Au-modified MEA showed mechanical durability upon ultrasonic treatment for up to an hour. Significance. Electro-codeposition of Ag:Au alloy combined with chemical etching Ag is a low-cost process for fabricating nanoporous Au-modified MEA suitable for establishing the stimulus–response relationship of cultured neuronal networks.