Microfabricated temperature-sensing devices using a microfluidic chip for biological applications

Microelectromechanical systems (MEMS) and micro-total analysis systems (μTAS) have been developed using microfabrication technologies. As MEMS and μTAS contribute to smaller, higher-performance, less expensive, and integrated sensing techniques, they have been applied in many fields. In this paper, we focus on microfabricated thermal detection devices, including a microthermistor fabricated using vanadium oxide (VO_x) and a resonant thermal sensor integrated into a microfluidic chip, and we present the research work we have done into biological applications, applications using a unique material and detection method for liquid samples. The VO_x thermistor, which has a high temperature coefficient of resistance at –1.3%/K, is mounted onto a thermally insulated membrane in the microfluidic chip. This device is used to detect glucose and cholesterol concentrations in solutions. The resonant thermal sensor is another candidate for obtaining highly sensitive thermal measurements; however, this sensor is difficult to use with liquids because of vibration damping and thermal loss. To solve these problems, we propose a partial vacuum packaging system for the sensor in the microfluidic chip. This technique, which involves silicon resonators, was used to successfully detect the heat from a single brown fat cell. Moreover, the possibility of using a VO_x resonant thermal sensor is discussed. The future prospects for MEMS and automation technology are described, with a focus on the Internet of Things/big data for medical and healthcare applications.