Open-Source Potentiostat for Wireless Electrochemical Detection with Smartphones

Abstract

This paper describes the design and characterization of an open-source "universal wireless electrochemical detector" (UWED). This detector interfaces with a smartphone (or a tablet) using "Bluetooth Low Energy" protocol; the smartphone provides (i) a user interface for receiving the experimental parameters from the user and visualizing the result in real time, and (ii) a proxy for storing, processing, and transmitting the data and experimental protocols. This approach simplifies the design, and decreases both the size and the cost of the hardware; it also makes the UWED adaptable to different types of analyses by simple modification of the software. The UWED can perform the most common electroanalytical techniques of potentiometry, chronoamperometry, cyclic voltammetry, and square wave voltammetry, with results closely comparable to benchtop commercial potentiostats. Although the operating ranges of electrical current and voltage of the UWED (±1.5 V, ±180 μA) are more limited than most benchtop commercial potentiostats, its functional range is sufficient for most electrochemical analyses in aqueous solutions. Because the UWED is simple, small in size, assembled from inexpensive components, and completely wireless, it offers new opportunities for the development of affordable diagnostics, sensors, and wearable devices.

Figure 1

Panels (A) and (C) show how the UWED functions. The working, reference, and counter electrodes are plugged into the UWED which is connected to a smartphone via BLE. A host program in the smartphone controls the experimental protocol, processes, visualizes, and stores the data, and transmits it to the Cloud. (B) shows the circuit diagram and main components of UWED.

Figure 2

Comparison between the performance of UWED and a commercial benchtop potentiostat [(A) EMF 16, Lawson Laboratories Inc.; (B) Autolab, PGSTAT12], in techniques of potentiometry and chronoamperometry. (A) Potentiometric measurement of the concentration of K⁺ using an ion-selective electrode and a commercial reference electrode. (B) Chronoamperometric measurement of potassium ferricyanide (1 mM–250 μM) on a screen-printed electrode. The inset shows the theoretically expected linear correlation of current (sampled at 1.0 s) and concentration of ferricyanide.

Figure 3

Cyclic voltammogram of 1 mM ferricyanide on a screen-printed electrode at scan rate of 100 mV/s. The inset shows the theoretically expected linear relationship of peak current and square root of scan rate.

Figure 4

(A) shows the square wave voltammogram recorded in a 1 mM ferricyanide solution measured by UWED and the commercial potentiostat (step size 5 mV, amplitude 50 mV, frequency 10 Hz). (B) shows the theoretically expected linear correlation between the peak amplitude and concentration of ferricyanide.