A Current-Driven Six-Channel Potentiostat for Rapid Performance Characterization of Microbial Electrolysis Cells

Abstract

Knowledge of the performance of microbial electrolysis cells under a wide range of operating conditions is crucial to achieve high production efficiencies. Characterizing this performance in an experiment, however, is challenging due to either the long measurement times of steady-state procedures or the transient errors of dynamic procedures. Moreover, wide parallelization of the measurements is not feasible due to the high measurement equipment cost per channel. Hence, to speedup this characterization and to facilitate low-cost, yet widely parallel measurements, this paper presents a novel rapid polarization curve measurement procedure with a dynamic measurement resolution that runs on a custom six-channel potentiostat with a current-driven topology. As case study, the procedure is used to rapidly assess the impact of altering pH values on a microbial electrolysis cell that produces H 2 . A ×2-×12 speedup could be obtained in comparison with the state-of-the-art, depending on the characterization resolution (16-128 levels). On top of this speedup, measurements can be parallelized up to 6× on the presented, affordable-42$-per-channel-potentiostat.

An Affordable Multichannel Potentiostat with 128 Individual Stimulation and Sensing Channels

“…The system outclasses the SotA PCB systems on the amount of individual stimulation (20x) and sensing (5x) channels for only a fraction of the cost (4x lower) and area (5x smaller). Furthermore, the channel performance matches the SotA, except for the relative performance of [8] and the number of bits in [7], although no effective accuracy is reported. A small steady-state voltage ripple is present at the output.…”

“…A single potentiostat channel contains only one dedicated component, a capacitor, while the other components can be time-shared across channels. As a result, the cost-per-channel is reduced to < 5$, 4x lower than the SotA [4], and the area-per-channel is reduced to ≈ 93 mm 2 , 5x lower than the SotA [4], [8]. Despite the 128 low-cost and low-area channels, the channelto-channel mismatch is reduced to < 1%.…”

“…The minimal T on is determined by the speed of the controllable current pump. During switching, a small transient charge flows because of the finite rise-time (T r ≈ 4 µs) and fall-time (T f ≈ 4 µs) of the current pump [8]. This unknown, transient charge must be much lower than the supplying charge to not affect the accuracy.…”

“…3) is implemented with an eight-channel, 16bit DAC (DAC8586, TI), connected to eight bipolar current pumps. Each current pump is implemented according to [8] but with a different current scaling resistor value (35.7 kΩ instead of 511 Ω) to obtain a more sensitive current range (±100 pA • • • ± 3.3 µA). Each current pump is then connected to the channel capacitors using a 1x16 analog multiplexer (MUX506, TI).…”

“…To date, the maximum number of individual parallel stimulation channels is six using PCB technology [8] and an impressive 64 using cmos technology [9]. Unfortunately, these 64 channels have only on-chip electrodes, which are very small, and require a difficult and again expensive postprocessing procedure to make them biocompatible.…”