From Antenna Stents to Wireless Geiger Counters: The Promise of Electrical Micro-Discharges in the Fabrication and Operation of Microsensors

Micro-scale electrical discharges can be useful in both manufacturing contexts and sensing modalities. With regard to manufacturing, they provide structural and material diversity: microplasmas ignited between thin film metal patterns permit localized etching and deposition, whereas micro-arcs permit stainless steel and other bulk metals. Micro-electrodischarge machining has been used for the lithography-compatible fabrication of "smart stents" that are integrated with pressure sensors. It has also been used to embed sensors at the tip of biopsy needles. With regard to sensing modalities, spectroscopic detection of chemicals in both gas and liquid phase has been explored. For example, discharge spectroscopy has been used to detect inorganic contaminants such as lead and chrome in water. The converse application has also been reported: salts dissolved in aqueous sample are used to tune the emission spectrum, which is subsequently filtered and used as an inexpensive UV source for the fluorescent detection of biochemicals. Gas-phase discharges are used for radiation sensing by Geiger counters and related micromachined devices. It has been shown that the RF emissions associated with these discharges are in the UWB spectrum, and can be detected by common AM/FM radios, creating some interesting opportunities for wireless networking