S. Swaminathan, J. Twiddy, J. Linnabary, R. Gundami,E. Cove, D. Probst, C. Sharkey, K. Peterson, M. Rubio, K. Sode, M. Daniele
North Carolina State University, University of North Carolina at Chapel Hill,
United States
Keywords: electrochemistry, potentiostat, biosensor, wearable, discrete, miniaturized
Summary:
Electrochemical sensors occupy a leading role within modern biomedicine, accounting for approximately 80% of the $30 billion global biosensors market. Many of these biosensors are used in point-of-care settings, where system size and cost represent major hurdles for widespread deployment; this is best exemplified by the explosive growth continuous glucose monitors, which have revolutionized blood glucose management for patients living with diabetes. Key to these and other electrochemical biosensor systems is the potentiostat, a circuit which enables precise control of potential applied to a sample and measurement of the resulting current. In addition to directly facilitating biosensing, potentiostats are used for electrode preparation – including cleaning and deposition of films – as well as electrosynthesis of pharmaceuticals, and direct wound care through the generation of reactive oxygen species at active wound sites. Conventional potentiostats are large, expensive benchtop instruments, unsuitable for field use. Recent efforts in both the commercial space (e.g., the Sensit Wearable by PalmSens and Analog Devices) and academic research have attempted to address this limitation, but substantial room for improvement remains; this is particularly true in the case of current commercial offerings, which are still too expensive (>$1,000 USD) for widespread deployment. While substantial effort has been expended on application-specific integrated circuits (ASICs) which implement analog frontends (AFEs) suitable for use in a potentiostat system, the vast majority of these are never commercialized. Commercial potentiostat AFEs (such as the LMP91000, AD594x, ADuCM35x, and related series) offer convenient turnkey solutions for general-purpose use, however they offer limited reconfigurability for targeted applications. A need exists for a greater diversity of modular, reconfigurable systems for electrochemical biosensing in wearable, point-of-care, point-of-patient, and edge sensing applications; this is particularly true in contexts involving unusual end-user requirements, including large numbers of channels or multiplexing, transduction of atypical current ranges, very high or low scan rates, the generation of more complex perturbation waveforms, and increased resolution. To this end, we have created a discrete potentiostat AFE focused on miniaturization, implemented in two forms: a reconfigurable AFE-only module (121 square millimeters) designed for rapid integration within a larger bespoke system, and a set of fully-integrated mobile devices (below 225 square millimeters) featuring a complement of supporting components (microcontroller, wireless interface, and power management) to enable fully-standalone deployment; both devices require <$100 USD in components. We performed fundamental benchtop electrical characterization, examining the ability of the AFE to faithfully maintain a target WE potential and accurately transduce cell current. This is followed by a series of in vitro experiments demonstrating functionality expected of a potentiostat, including detection of a range of analytes (lactate, ferricyanide, β-hydroxybutyrate) and the deposition of polyaniline (PANI) onto an electrode using cyclic voltammetry (CV). This miniaturized AFE is intended as both a standalone tool for direct use in research, and for integration within larger bespoke systems to facilitate the next generation of electroanalytical sensors and devices.