Self-Powered Potentiometric Sensor Transduction to a Capacitive Electronic Component for Later Readout

Abstract

Potentiometric sensors operate as galvanic cells where the voltage is spontaneously generated as a function of the sample composition. We show here that energy can be harvested, stored during the sensing process without external power, and physically isolated from the sensor circuit for later readout. This is accomplished by placing an electronic capacitor as a portable transduction component between the indicator and the reference electrode at the point where one would ordinarily connect the high-input-impedance voltmeter. The voltage across this isolated capacitor indicates the originally measured ion activity and can be read out conveniently, for example, using a simple handheld multimeter. The capacitor is shown to maintain the transferred charge for hours after its complete disconnection from the sensor. The concept is demonstrated to detect the physiological concentrations of K + in artificial sweat samples. The methodology provides a readout principle that could become very useful in portable form factors and opens possibilities for potentiometric detection in point-of-care applications and inexpensive sensing devices where an external power source is not desired.

Potentiometric Sensing

“…Alternatively, an external electronic capacitor was used for the transduction of the potentiometric sensor signal in an elegant way by Bakker and Sabaté’s research groups . Instead of using a high input impedance voltmeter, the authors placed an electronic capacitor between the indicator and the reference electrode (see Figure ).…”

“…Using an electronic capacitor for energy transfer and later potentiometric readout . The electronic capacitor is placed between the indicator and reference electrodes.…”

“…Alternatively, an external electronic capacitor was used for the transduction of the potentiometric sensor signal in an elegant way by Bakker and Sabate's research groups. 42 Instead of using a high input impedance voltmeter, the authors placed an electronic capacitor between the indicator and the reference electrode (see Figure 3). In this configuration, the potential change between the indicator and the reference electrode was directly transferred onto the capacitor to keep the overall potential difference of the closed loop at zero.…”

Ionophore-based ion-selective electrodes: signal transduction and amplification from potentiometry

“…To eliminate the baseline drift and shorten the sample time, Bakker and coworkers recently proposed a coulometric method for ISEs by introducing an electronic capacitor into the electrochemical cell. [33][34][35][36][37] As shown in Fig. 2a, the electronic capacitor was connected in series with the ISM.…”

“…A self-powered sensing concept was introduced based on the capacitors and successfully applied to detect physiological concentrations of K + in artificial sweat samples. 37 Furthermore, information memorized in the capacitor could be used to develop deployable sensors to monitor sample changes within a defined period of time. This was recently demonstrated to identify incurred pH changes in a river water sample during an interval of 2 h. 36 Therefore, adding electronic capacitors to ISEs not only increased the sensitivity but also resulted in new applications that are inaccessible with traditional potentiometry.…”