Wireless Sensor Systems for In-Vivo Applications

Abstract

Rapid developments in microelectronics technology have allowed for phenomenal achievements in biomedical engineering. In the past few decades, an enormous amount of researches were done in the field of medical implantable microelectronic systems. The prevalence of research in this particular field have led to the design of novel systems for in-vivo applications, for example, using microelectronic systems to replace catheterization in clinical studies of urinary incontinence. In this thesis research, we study two types of wireless modules towards our goal of wireless systems for in-vivo applications. The first system, a 2.4 GHz wireless pressure sensor system, is designed as a pressure sensing module to operate as a part of a pill imaging device published in [32]. This pressure module samples pressure data and passes them to the pill imaging capsule via a serial-port-interface (SPI). The 2.4 GHz wireless pressure system has an overall system dimension of 75.0 x 20.5 x 17.5 mm3 with a current consumption of 5 mA when operating from a 3 V supply. The pressure sensitivity of this system is observed as 1.14 cmH20/LSB (least significant bit). The second system, 125kHz RFID (radio-frequency identification) dual sensor system, is designed to explore the possibility of powering the device and transmitting data using the RFID technology. The 125kHz RFID dual sensor system has an overall system dimension of 30.0 x 15.0 x 15.0 mm3 with a current consumption of 1.5 mA while operating at 3 V. The pressure sensitivity of this system is observed as 2.93 cmH20/LSB and the temperature sensitivity is observed as 0.069 °C/LSB. And, the detections of rapid pressure changes in both systems are successful. The work performed in this thesis research has provided a cost-effective method of designing medical implantable systems using off-the-shelf components as compared to full-custom designs. In this research, it is also observed that power consumption is a major issue in medical implantable systems. Finally, the possibility of transmitting data and powering such systems using RFID technology has been verified.