Tongtawee Wacharasindhu

Radioisotope microbattery based on liquid semiconductor

A liquid semiconductor-based radioisotope micropower source has been pioneerly developed. The semiconductor property of selenium was utilized along with a 166 MBq radioactive source of S35 as elemental sulfur. Using a liquid semiconductor-based Schottky diode, electrical power was distinctively generated from the radioactive source. Energetic beta radiations in the liquid semiconductor can produce numerous electron hole pairs and create a potential drop. The measured power from the microbattery is 16.2 nW with an open-circuit voltage of 899 mV and a short-circuit of 107.4 nA.

Liquid-semiconductor-based micro power source using radioisotope energy conversion

In this paper, we present a betavoltaic micro power source using liquid-semiconductor for the first time. We have fabricated and characterized a MEMS-based micro battery, which is powered by a radioactive source with a liquid-semiconductor-based Schottky diode. Semiconductor properties of liquid selenium are utilized with radioactive sulfur (35S) for direct power conversion. The radioisotope material is encapsulated with liquid semiconductor in a micromachined device. Experimental results show that maximum of 16.2nW can be harvested from the micromachined liquid semiconductor Schottky diode. A large open-circuit voltage of 899mV and short-circuit current of 0.107µA were also observed.

Mechanisms Leading to Losses in Conventional Betavoltaics and Evolution: Utilizing Composite Semiconductor With Infused Radioisotope for Efficiency Improvement

In this paper, we demonstrate remarkably improved efficiency over various conventional betavoltaics with critical energy loss problems. Radioactive sulfur (35S) was uniformly infused within a semiconductor material (selenium) and volumetrically encapsulated in the harvesting betavoltaic cells. By eliminating or reducing the potential loss factors with this new method, highly efficient energy conversion was achieved compared with conventional approaches. First and second generation prototype devices were fabricated and tested. A maximum output power of 687 nW was obtained from the micropower source using 33.61 mCi of 35S. The overall efficiency of the prototype device was 7.05%.

Flashover prevention of high voltage piezoelectric transformers

Piezoelectric transformers are used as step-up voltage elements in many devices [1, 2]. The University of Missouri is developing a piezoelectric transformer as an accelerator for an ion beam [3]. In cases where high voltage pulses are desired, discharges can result from a large electric field near triple point junctions [4, 5]. Due to the small scale of the device, conductive triple point shields are difficult to employ to prevent flashover. This paper presents an investigation of piezoelectric flashover prevention by thin film encapsulation. Dielectric material was deposited on the piezoelectric transformer both over the entire device, and at specific regions of interest. The dielectric was deposited by evaporation to eliminate gaps at the triple point. The flashover strength is evaluated depending on the dielectric type, thickness, and length. The mechanical loss incurred by the deposition is evaluated to determine if it hinders the motion of the transformer.

Flashover Prevention of High Voltage Piezoelectric Transformers by Thin Film Encapsulation

Piezoelectric transformers (PTs) are used as step-up voltage elements in many devices. The University of Missouri is developing a PT as an accelerator for an ion beam. In cases where high-voltage pulses are desired, discharges can result from a large electric field near triple point junctions. Due to the small scale of the device, conductive triple point shields are difficult to employ to prevent flashover. This paper presents an investigation of piezoelectric flashover prevention by thin film encapsulation. Dielectric material was deposited on the PT both over the entire device and at specific regions of interest. The dielectric was deposited by evaporation to eliminate gaps at the triple point. The flashover strength is evaluated depending on the dielectric type, thickness, and length. The mechanical loss incurred by the deposition is evaluated to determine if it hinders the motion of the transformer.