This wireless potentiostat is based on the ADuCM355 SoC from Analog Devices, tailored for portable electrochemical sensing. This device, engineered on a custom PCB, brings laboratory-level electrochemical analysis to the field with a significantly reduced footprint and cost. The potentiostat integrates critical functions like potentiostat amplifiers, digital-to-analog converters (DACs), analog-to-digital converters (ADCs), and a microcontroller within the ADuCM355 IC. This highly integrated approach allows the design to minimize interconnects, which often lead to noise and signal loss in non-integrated systems. Using a four-layer PCB further optimizes performance, with dedicated power and ground planes in the middle layers for reduced noise propagation. The potentiostat also includes a USB-C connector for power and data transfer, enabling it to communicate seamlessly with computers or mobile devices through a USB-to-Serial interface chip.

While maintaining its compact size, the potentiostat's wireless functionality allows it to connect to mobile devices or computers for real-time data display and control. For this, we have utilised an ESP32 SoC as a wireless bridge, with the help of custom firmware. This feature is implemented via a graphical user interface (GUI) available on Android and Windows. The GUI allows users to set parameters for different electrochemical methods, including cyclic voltammetry (CV), square wave voltammetry (SWV), and electrochemical impedance spectroscopy (EIS). Results can be viewed immediately, saved, and exported in CSV format for detailed analysis.

Here are the PCB layers.

Schematic Diagram

Now let's look at the schematics for the wireless potentiostat.

Here we have used a USB type C port for charging the device, communication and firmware upgrade for the Wireless SoC. For charging the internal battery we have used the infamous TP4056 single-cell Li-ion battery charger chip since it is cheap and does the job well enough. For communication, I have opted for a CP2102N USB to UART controller chip from Silicon Labs because it performs well even with a higher baud rate and comes in a very compact package. And as for wireless communication, we are using an ESP32 SoC as a wireless UART bridge. I have also added precision to use a CH340K instead of CP2102 if needed. For powering the 3.3V logic we have used an ultra-low noise LDO, an ADM7154 from Analog Devices.

Apart from that the heart of the potentiostat is an ADuCM355 SoC from Analog Devices. The ADuCM355 Precision Analog Microcontroller offers an on-chip system that controls and measures electrochemical sensors and biosensors. This MCU comes with a chemical sensor interface and facilitates a mixed signal MCU which is based on Arm Cortex-M3 processor. The ADuCM355 Analog MCU is capable of current, voltage, and impedance measurements and features a 16-bit, 400kSPS ADC with ultralow leakage switch matrix and input MUX. This MCU operates at a 2.8V to 3.6V supply range and a -40°C to 85°C ambient temperature range. Typical applications include gas detection, food quality, blood glucose meters, and bioimpedance measurements.

The project is based on the Acestat project from ERDC. The new design included wireless functionality onboard battery charging and an optimised PCB layout for better results. Full details including hardware design files and firmware source code can be found on the Wireless potentiostat GitHub Repo.