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A High-Performance and Cost Effective Hydrogen Sensor
(Research team of Professor Park, Professor Jung, and research fellow Gao Min) A KAIST research team reported a high-performance and cost effective hydrogen sensor using novel fabrication process based on the combination of polystyrene nanosphere lithography and semiconductor microfabrication processes. The research team, led by Professor Inkyu Park in the Department of Mechanical Engineering and Professor Yeon Sik Jung in the Department of Materials Science and Engineering, fabricated a nanostructured high-performance hydrogen gas sensor based on a palladium-decorated silicon nanomesh structure made using a polystyrene nanosphere self-assembly method. Their study was featured as the front cover article of journal “Small” (Publisher: Wiley-VCH) on March 8, 2018. The nanosphere lithography method utilizes the self-assembly of a nanosphere monolayer. This could be an alternative choice for achieving uniform and well-ordered nanopatterns with minimum sub-10 nanometer dimensions. The research team said that the small dimensions of the silicon enhanced the palladium-gating effect and thus dramatically improved the sensitivity. Hydrogen gas is widely considered to be one of the most promising next-generation energy resources. Also, it is a very important material for various industrial applications such as hydrogen-cooled systems, petroleum refinement, and metallurgical processes. However, hydrogen, which is highly flammable, is colorless and odorless and thus difficult to detect with human senses. Therefore, developing hydrogen gas sensors with high sensitivity, fast response, high selectivity, and good stability is of significant importance for the rising hydrogen economy. Silicon nanowire-based devices have been employed as efficient components in high-performance sensors for detecting gases and other chemical and biological components. Since the nanowires have a high surface-to-volume ratio, they respond more sensitively to the surrounding environment. The research team’s gas sensor shows dramatically improved hydrogen gas sensitivity compared with a silicon thin film sensor without nanopatterns. Furthermore, a buffered oxide etchant (BOE) treatment of the silicon nanomesh structure results in an additional performance improvement through suspension of nanomesh strutures from the substrate and surface roughening. The sensor device shows a fast hydrogen response (response time < 5 seconds) and 10 times higher selectivity to hydrogen gas among other gases. Their sensing performance is stable and shows repeatable responses in both dry and high-humidity ambient environments. Professor Park said that his approach will be very useful for the fabrication of low-cost, high-performance sensors for chemical and biological detection with applications to mobile and wearable devices in the coming era of internet of things (IoTs). (Figure 1: The front cover image of Small dated on March 8.) (Figure 2: Gas sensor responses upon the exposure to H2 at various concentrations.)
KAIST Develops Subminiature, Power-Efficient Air Pollution Sensing Probe
Professor Inkyu Park and his research team from the Department of Mechanical Engineering at KAIST have developed a subminiature, power-efficient air-pollution sensing probe that can be applied to mobile devices. Their research findings were published online in the January 30th issue of Scientific Reports. As air pollution has increased, people have taken greater interest in health care. The developed technology could allow people to measure independently the air pollution level of their surrounding environments. Previous instruments used to measure air pollution levels were bulky and consumed a lot of power. They also often produced inaccurate results when measuring air pollution in which different toxic gases were mixed. These problems could not be resolved with existing semiconductor manufacturing process. Using local temperature field control technology, Professor Park’s team succeeded in integrating multiple heterogeneous nanomaterials and fitting them onto a small, low-power electronic chip. This microheating sensor can heat microscale regions through local hydrothermal synthesis. Because it requires a miniscale amount of nanomaterials to manufacture, the sensor is most suitable for mobile devices. Professor Park said, “Our research will contribute to the development of convergence technology in such field as air pollution sensing probes, biosensors, electronic devices, and displays.” The team's research was supported by the Ministry of Education and the Ministry of Science, ICT and Future Planning, Republic of Korea. Figure 1 – The Concept of Multiple Nanomaterial Device and Numerical Simulation Results of Precursor Solutions Figure 2 - Multiple Nanomaterial Manufactured in a Microscale Region
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