Performance characteristic studies of glucose biosensors modified by (3-mercaptopropyl)trimethoxysilane sol–gel and non-conducting polyaniline

The materials (3-mercaptopropyl)trimethoxysilane (MPTMS) sol–gel and non-conducting polyaniline (PAn) were prepared for coating on two different amperometric biosensors fabricated by the immobilization of glucose oxidase (GOx) in conducting polyaniline (PA) as permselective membranes. A few performance characteristics of the MPTMS and the PAn-modified glucose sensors are comparable. In detecting 1 mM glucose, the biosensors’ response times were 11 and 12 s, respectively, and results from the repeating measurements (N = 10) showed that R.S.D. = 2.09 and 1.70%, respectively. The detection linearity of the two biosensors was up to 12.5 mM with R = 0.9989 and 0.9969. When they were used to detect 0.5 mM of ascorbic acid (AA), uric acid (UA), and acetaminophen at an anodic potential of 0.4 V, current signals were either insignificant or invisible. The PAn-coated glucose sensor exhibited superior sensitivity at 18.91 μA/(mM cm²), and a maximum current density of 3.70 mA/cm². GOx in the MPTMS-modified biosensor presented a stronger affinity to glucose with K_m = 48.87. More importantly, the stability of this biosensor is superior to that of the PAn-modified biosensor and has lasted for almost 5 months.     

A 2 MHz Wireless CMOS Transceiver for Implantable Biosignal Sensing Systems

An implementation of an implantable sensing biosystem composes of a readout circuit, a power management block, an embedded microcontroller unit (MCU), an implantable drug delivery section and a wireless uplink transceiver system. This paper describes a bi-directional wireless transceiver system for implantable sensing systems. The transceiver system is composed of an external and implantable transceiver, communicating through an inductive link. Half duplex communication between transceivers at a 10 Kbps data rate was achieved at a maximum distance of 4 cm. Command and data will be supplied to the implantable module by radio frequency (RF) telemetry utilizing an amplitude shift keying (ASK) modulated 2 MHz carrier frequency. A capacitor-less amplitude demodulation receiver architecture was produced in the research with implantable receiver core area measuring at 113.2 μm by 171.8 μm with average power dissipation at 815.1 μW at a 3.3 V single rail power supply. An active uplink transceiver utilizing load shift keying (LSK) as backward data telemetry was designed. Implantable transmitter core area measures 251.7 μm by 139.3 μm, consuming 103.62 mW while driving an RF ferrite core antenna at maximum reading range. Integrating both circuits, implantable transceiver, measuring 355.3 μm by 171.8 μm, was designed and implemented using TSMC 0.35 μm mixed-signal 2P4M 3.3 V standard CMOS process. The integrated circuit solution addressed solutions for many of the problems associated with implanted devices and introduces circuits which improve in several ways over previously published designs, in functionality and integration level. In addition to being fully integrated in plain CMOS technology, not relying at least partly on available specialized elements and expensive technologies, these building blocks improve on previous designs in performance and/or power consumption. This work succeeded in implementing building blocks for an implantable transceiver, which depends only on the absolute minimum off-chip components. A complete implantable chip is presented, which highlight the design tradeoffs and optimizations applied to the design of CMOS implantable system chips.