A Thermoelectric (TE) generator is expected to play an important role in the operation of tiny-watt capable wireless power supply devices by converting the waste heat energy into electrical energy. This work is the demonstration of planar cavity-free multi-stage n-type unileg- and bileg Si-nanowire (Si-NW) TE generators. The result shows that the output power of the multi-stage bileg-TE generator increases linearly with increasing the stage number, whereas the rate of increase of the multi-stage unileg-TE generator power output tends to decrease as the stage number increases. Although the power of the multi-stage bileg-TE generator fabricated in this work was smaller than that of the multi-stage unileg-TE generator due to the large internal resistance of p-type elements, however, the improved linearity of the bileg-TE generator than the unileg-TE generator indicates the potential advantage of the multi-stage bileg-TE generator for the large-scale integration.

Heat guide (HG) is a layer providing a heat flux to a desired part in micro thermoelectric generator (µ-TEG). In this work, we experimentally investigated the impact of the HG structure on the thermoelectric voltage of a cavity-free planer-type Si-nanowire (Si-NW) µ-TEG, which is embedded in SiO2 acting as an inter-layer dielectric (ILD). Although the heat flows also through the ILD, a sub-µm-thick HG is able to selectively guide the heat flux to hot side terminal of the µ-TEG, and the µ-TEG performance is improved by increasing the thickness of the HG.

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The effect of the spreading resistance on the bileg thermoelectric generator (TEG) performance was experimentally evaluated. In planar bileg-TEGs, the width ratio of the p- and n-type legs should be carefully selected to compensate for the impedance mismatch between them and to maximize thermoelectric power generated from an unit area. In the bileg-TEG at the μm-scale, the electrical resistance becomes larger than a simple estimate using lumped parameter circuit model, which is caused by the spreading resistance; when a current flows from a narrower leg to a wider leg. A distance of greater than about 10 μm is required to distributed the electric current over the entire region of the wider leg. At shorter leg length, it is better to align the widths of p- and n-legs to maximize the areal power density of TEG. Decreasing the electrical resistance of the wiring between the p- and n-legs is also effective in enhancing the performance of the miniaturized TEG. The width of the p- and n-type legs in the bileg-TEG at the μm-scale should be carefully selected.

Purpose: During computed tomography (CT) examinations, it may be necessary to assist the patient to maintain an appropriate body position. However, there is little protective equipment available for caregivers who approach the gantry. This study aimed to evaluate the effectiveness of novel radiation protective curtains in reducing radiation exposure to caregivers while assisting patients, especially during CT examinations of the head. Method: The absorbed dose in air around the gantry during CT examinations of the head was measured using glass dosimeters. The measurement points from the center of the gantry were 40 to 120 cm in the front, 0 to 100 cm for each side in the right and left, and 60 to 180 cm from the floor. Measurements were performed at each 20-cm interval, and all points were accumulated 10 times. The absorbed dose in air in a CT room was compared with and without the protective curtains. Next, we assumed the height of the caregiver to be 170 cm, and measured the points for the crystalline lens, chest, and abdomen. Also, using the protective glasses and the protective apron, we measured the absorbed dose in air for the caregivers behind the protective curtains. Result: The absorbed exposure dose in air toward the crystalline lenses, chest, and abdomen was reduced more than 90% by using the protective curtains and more than 95% by using the protective apron and protective glasses in addition to them. Conclusion: This study showed the usefulness of protective curtains in reducing the absorbed exposure dose in air to caregivers.