A programmable energy efficient readout chip for a multiparameter highly integrated implantable biosensor system

Abstract

Abstract.In this work an Application Specific Integrated Circuit (ASIC) for an implantable electrochemical biosensor system (SMART implant, Stett et al., 2014) is presented. The ASIC drives the measurement electrodes and performs amperometric measurements for determining the oxygen concentration, potentiometric measurements for evaluating the pH-level as well as temperature measurements. A 10-bit pipeline analog to digital (ADC) is used to digitize the acquired analog samples and is implemented as a single stage to reduce power consumption and chip area. For pH measurements, an offset subtraction technique is employed to raise the resolution to 12-bits. Charge integration is utilized for oxygen and temperature measurements with the capability to cover current ranges between 30 nA and 1 µA. In order to achieve good performance over a wide range of supply and process variations, internal reference voltages are generated from a programmable band-gap regulated circuit and biasing currents are supplied from a wide-range bootstrap current reference. To accommodate the limited available electrical power, all components are designed for low power operation. Also a sequential operation approach is applied, in which essential circuit building blocks are time multiplexed between different measurement types. All measurement sequences and parameters are programmable and can be adjusted for different tissues and media. The chip communicates with external unites through a full duplex two-wire Serial Peripheral Interface (SPI), which receives operational instructions and at the same time outputs the internally stored measurement data. The circuit has been fabricated in a standard 0.5-µm CMOS process and operates on a supply as low as 2.7 V. Measurement results show good performance and agree with circuit simulation. It consumes a maximum of 500 µA DC current and is clocked between 500 kHz and

Materials and Biomedical Applications of Implantable Electronic Devices

“…The potentiometric sensors are to detect the change of the charge density at the surface of the electrode. [ 194 ] Recently, the implantable potentiometric sensors have been fabricated for in vivo real‐time monitoring of ischemia on the stomach tissue (Figure 6d), [ 195 ] temperature measurements, [ 196 ] cytochrome c sensing, [ 197 ] etc.…”

“…No commercially available products. [194][195][196][197] Conductometric biosensors Gauging the change in ionic conductance or impedance between electrodes; no reference electrode is needed.…”

Design of a CMOS readout circuit on ultra-thin flexible silicon chip for printed strain gauges

“…Aerosol Jet ® printing technique, also known as maskless mesoscale material deposition (M 3 D), is utilized in this work to print the strain gauges on the BCB/PI substrate (Hedges et al, 2005;Paulsen and Renn, 2014). In this technology, the silver ink is atomized and converted into a dense aerosol, which is transported to the print head using an inert carrier gas.…”

“…The digital operation uses a main clock with frequency of 864 kHz. Note that the influence of bending on the digital transistors and thus the digital circuit performance in terms of setup and hold times is minimized by increasing the base uncertainty during circuit synthesis (Mahsereci et al, 2016). Figure 5 shows the schematic of the implemented analog interface circuit.…”

“…The minimum chip thickness and mechanical flexibility features are also desirable for several emerging applications such as bio-medical implants, electronic skin, Hybrid Systems-in-Foil and flexible displays (Burghartz et al, 2009). For example, the minimum chip thickness provides the capability to have an implantable bio-sensors platform (Nawito et al, 2015;Kim et al, 2013). In addition the mechanical flexibility of the ultra-thin silicon chip is utilized to implement a stress sensor chip, where on-chip MOS transistors oriented in different directions act as sensing elements, while implementing a relatively stress-insensitive readout circuit (Mahsereci et al, 2016;Kuhl et al, 2013).…”