DAPPER is a front end system capable of simultaneous amperometric and potentiometric sensing proposed for lowpower multi-parameter analysis of bio-fluids such as saliva. The system consists of two oscillator circuits, generating a frequency relative to their sensed current and voltage signals. These signals are then mixed together to produce a single channel output that can be transmitted through backscattering (load-shift keying). The entire system consumes 40µW from a 1.4V supply. The linear ranges of potentiometry and amperometry circuits are 0.4V -1V and 250pA -5.6µA (87dB), and their input referred noise is 1.7µV and 44.6fA, respectively.

Potentiometry and amperometry are the two most common electrochemical sensing methods. They are conventionally performed at different times, although new applications are emerging that require their simultaneous usage in a single electrochemical cell. This paper investigates the feasibility and potential drawbacks of such a setup. We use a potentiometric and an amperometric sensor to compare their output signals when they are used individually, as well as when they are combined together with a shared reference electrode. Our results in particular show that potentiometric readings with a shared reference electrode show a high correlation of 0.9981 with conventional potentiometry. In the case of amperometric sensing, the cross correlation of the simultaneous versus individual measurement is 0.9959. Furthermore, we also demonstrate concurrent measurement for potentiometry in the presence of cell current through the design of innovative test systems. This is done through measuring both varying pH values and varying concentrations of H 2 O 2 to showcase the operation of the circuit.

An indication of the dental health of patients can be observed from the pH levels of their saliva. This work presents a first prototype of a smart Orthodontic Bracket (SOB) for continuous monitoring of pH in mouth. The SOB system uses Iridium Oxide (IrOx) pH sensor with 68.8 mV/pH measured sensitivity and is powered through Near Field Communications (NFC) using a smart-phone from a distance of 3.5 cm. The system resolves pH change of 0.15 within a wide range of pH. The system is encapsulated in bio-compatible Epoxy resin and successfully used to measure the pH in Saliva.

A wireless power management unit is presented in this work. The system size of 0.4mm 2 with the low power consumption of 87µW allow it to be applied in implantable biomedical applications and ex-vivo systems. The proposed system optimises the conventional slew-rate detection low dropout (LDO) circuit by using a self-tuned controlling block that reduces the response time to 100ns. The static power required for this LDO is reduced to 2µW. The band gap reference (BGR) is designed with a high power supply rejection ratio (PSRR) of 60dB at 100kHz, along with an output reference voltage deviation of 1mV, to deal with the power supply ripple caused by the load shift keying (LSK). The RF power is transmitted at 433MHz and the internal power management circuit is able to provide a 1.4V stable DC supply for a front end on-chip sensor.

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This work describes the implementation of SPACE-Man, a wireless electrochemical system with concurrent potentiometric and amperometric sensing that can be utilised for saliva, sweat or point of care diagnostics. This system is designed with the vision of simpler interfaces for biofluid analysis. With a complete system-on-chip including electrochemical sensing, power management and data transmission, conventional interfaces like wirebonds will no longer be required in post-processing steps. The proposed architecture consists of a sensor front-end with four electrodes for concurrent amperometric and potentiometric sensing. This front-end outputs square wave signals mixed together with varying frequencies dependent on the sensed input, with the output type switchable with a state machine. A power management system consisting of a low dropout regulator (LDO) band gap reference (BGR), and a rectifier bridge is utilised for supplying power from an inductive link at 433MHz. Sensor data is transmitted wirelessly to a base station using LSK (Load-Shift Keying). The sensor front-end consumes 18µW, which the power management system more than adequately provides. The core area of the electronics without the coil is a conservative size of 0.41mm 2 .

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