Applications of Physical Sensors in Biomedical Engineering: Present Scenario and Research Trends

Abstract

A physical sensor is an electronic device responsive to a physical property such as light, radiation, heat, flow, pressure, magnetic field and other parameters related to mass or energy. According to the signal, the physical sensors used in biomedicine are subdivided into classes of radiant, mechanical, thermal and magnetic signals. The present review paper gives a detailed description of the current status and future prospects of the chief physical sensors from

the viewpoint of biomedical applications. Under the radiation sensors, X-ray and gamma ray sensors are addressed. In the mechanical sensors, the operation of ultrasound and pressure sensors is explained. Among the thermal sensors, mention has been made of thermistor, thermocouple, thermopile, P-N junction diode, optical fibre devices and infrared

sensors. Optical fibre devices are promising devices offering enormous expectations. The important magnetic sensors include the blood flow sensor and magnetic resonance imaging system. Brief information on Doppler blood flow sensor is also presented.<br> Although most of the above sensors are being extensively used in electronic instrumentation in X-ray tomography, positron emission tomography, ultrasonography, magnetic resonance imaging, and for measurement of blood pressure, blood flow rate, body temperature, etc, in the hospitals, yet researchers working in the sensor laboratories worldwide are continuously striving for the development of more sensitive, stable, low-cost and reliable sensors. Stringent tests and experiments are being conducted for studying the reproducibility of fabrication technology of

these sensors. Their characteristic properties like sensitivity, linearity, selectivity, resolution, measurement range, hysterisis and response time, as well as repeatability of these properties is also being intensely investigated to enable large-scale production of these sensors. The trend of research in all the sensors is towards solid-state silicon sensors and optical-fibre devices. Miniaturization of the sensors is being done using semiconductor fabrication techniques of

microelectronics. The special advantage derived from silicon sensors is that by combining the sensor and the signal electronics on the same silicon chip, 'integrated smart or intelligent sensors' have been fabricated. Due to the combined and active participation of material scientists, physicists, chemists, biologists and engineering experts, the field of 'physical sensors' is progressing rapidly through the discovery of better sensing materials, replacement of

conventional electronic devices by silicon and optical-fibre devices, and the implementation of novel designs of these devices.