Haluk Beyenal

We developed a low-cost, portable four-channel potentiostat for simultaneous electrochemical measurements in soil. The instrument supports open-circuit potential monitoring, cyclic voltammetry, and chronoamperometry, with a programmable potential range of ±4.096 V and current-measurement configurations for large-area electrodes and microelectrodes. It operates on USB power or a Li-ion battery and includes onboard data storage and Bluetooth communication. Benchmarking against a commercial potentiostat in individual three-electrode cells showed comparable voltammetric responses under the tested conditions. We also evaluated simultaneous operation using shared reference and counter electrodes. In 40-d soil experiments, the instrument recorded current responses from carbon fabric electrodes polarized at different potentials and carbon-tipped microelectrodes positioned at different depths. These measurements demonstrated temporal variation and differences among electrode potentials and depths, including nanoampere-scale responses from microelectrodes. The results establish the instrument’s capability for simultaneous multielectrode soil measurements and for monitoring biofilm activity.

Physicochemical soil parameters drive biogeochemical processes by controlling microbial activity and the mobility, solubility, and bioavailability of organic and inorganic matter. Because these properties vary with depth, depth-resolved electrochemical tools are needed, yet existing systems are often limited in travel range, automation, cost, or flexibility. Here, we present a custom-built Soil Electrochemical Profiling System (SEPS) for water-saturated soils and other conductive porous media. Built from off-the-shelf components, the custom manipulator hardware can be assembled for less than $200, provides up to 27 cm vertical travel, and operates with a minimum mechanical step interval of 25 μm. SEPS integrates with a potentiostat to perform open-circuit-potential-based redox profiling, cyclic voltammetry, and chronoamperometry. We tested the system using ferricyanide/ferrocyanide standards and hydrogel diffusion experiments. We then demonstrated proof-of-concept applications in homogenized, water-saturated soil mesocosms, where SEPS resolved time- and depth-dependent redox changes and voltammetric responses. In addition, a polarized carbon-tip electrode supported long-term biofilm enrichment and subsequent depth-resolved chronoamperometric measurements. SEPS provides a practical, low-cost platform for electrochemical profiling in saturated soils, hydrogels, sediments, and related porous media.

Hydrogen is an essential fuel and feedstock that can be produced in multiple ways to meet requirements for technological sectors that include energy storage, transportation, petroleum refining, and ammonia synthesis. To consider the future state of hydrogen manufacturing, a team of experts has assembled and examined three emerging hydrogen production technologies – photoelectrochemical, biological, and thermochemical. Each of these emerging technologies holds significant long-term potential for cost reduction while lowering industrial emissions associated with conventional methods of hydrogen manufacture (e.g., steam methane reforming) by using sunlight and renewable resources as primary sources of energy and feedstock, respectively. All three are currently at low technology readiness levels, however their applications, cost reduction opportunities and performance improvement pathways are under active development. In this work, opportunities and outlook for research that can directly advance the technologies are discussed.

Biofilms hinder wound infection healing, making wound infections a healthcare challenge for which innovative treatments are needed. A 1.77 cm ² electrochemical bandage (e-bandage), which generates the biocide hypochlorous acid (HOCl), has shown promising anti-biofilm activity in vitro , ex vivo , and in vivo . The e-bandage is a three-electrode system operationalized by a hydrogel. In addition to providing a conductive electrolyte for the electrodes, the hydrogel provides a protective barrier for the wound. How different hydrogels impact e-bandage functionality is not completely defined. Here, the in vitro activity of seven clinically available hydrogels (xanthan gum, 3M, Duoderm, Prontosan, Purilon, Skintegrity, and Solosite) was evaluated with 1.77 cm ² HOCl-generating e-bandages using a potentiostat with a multiplexer in a membrane biofilm model against methicillin-resistant Staphylococcus aureus IDRL-6169 and Acinetobacter baumannii ATCC-17978. When applied with polarized HOCl-producing e-bandages, all evaluated hydrogels except Solosite yielded ≥5.5 log ₁₀ CFU/cm ² reductions in bacterial quantities after 6 h of treatment, with most being below the detection limit at that time point. Prontosan exhibited antibacterial activity independent of e-bandage. Results of this study inform the selection of clinically available hydrogels that may be suitable for use with a 1.77 cm ² HOCl-producing e-bandage. IMPORTANCE: In this study, it was shown that some clinically available hydrogels, combined with a 1.77 cm ² HOCl-generating electrochemical bandage, deliver time-dependent antimicrobial activity against methicillin-resistant Staphylococcus aureus and Acinetobacter baumannii biofilms, offering a potential approach to treat wound infections, including those caused by antimicrobial-resistant bacteria.

An electrochemical bandage (e‐bandage) that generates hydrogen peroxide (H ₂ O ₂ ) through a combination of working, counter and reference electrodes used with an electrolyte‐providing hydrogel is being developed for wound infection management. e‐Bandage biocidal activity was previously demonstrated using Xanthan gum hydrogel. For clinical use, clinically used hydrogels would be ideal, but their use with the described e‐bandage has not been shown. The goal of this work was to evaluate the biocidal activity of off‐the‐shelf, clinically used hydrogels when used with a 1.77 cm ² H ₂ O ₂ ‐producing e‐bandage. e‐Bandage electrochemical parameters and activity against methicillin‐resistant Staphylococcus aureus IDRL‐6169 and Acinetobacter baumannii ATCC‐17978 biofilms were assessed with six off‐the‐shelf hydrogels. Variations in hydrogel composition affected electrochemical parameters, which was associated with differences in biocidal activity. Results of this study inform the selection of off‐the‐shelf hydrogels for use with H ₂ O ₂ ‐producing e‐bandages.

Desert kangaroo rats ( Dipodomys deserti ) construct burrows that can create micro-niches favorable to increased microbial activity. The aim of this study was to characterize the bacterial communities found in kangaroo rat burrows, in proximal desert surface sand, and in samples from kangaroo rats. We collected samples from burrow ceilings of actively inhabited burrows, from burrows that were no longer in use, and from the proximal surface sand in the Sonoran Desert, Yuma, AZ. Following DNA extraction from samples, 16S rRNA gene sequencing was performed, and functional predictions were made and assessed for each characterized bacterial community. Active burrow samples exhibited greater alpha diversity but similar beta diversity when compared to surface sand ( P < 0.05), with no significant differences observed between abandoned and active burrows. Bacterial genera and genes related to nitrogen fixation, nitrification, and urea hydrolysis were found in significantly higher abundance in active burrows compared to the surface sand ( P < 0.05). The core microbiome of active burrow samples was different from surface sand, including higher abundances of Acidimicrobiales and Acidobacteria subdivision Gp7. Active burrow samples included 30 unique genera. Kangaroo rat anal swabs shared 12, cheek pouches shared 6 unique genera with burrows. These findings suggest that kangaroo rats can shape the microbial composition of their burrow environment through the introduction of food material and waste, facilitating increased species richness and bacterial diversity. IMPORTANCE: Animals can alter soil parameters, including microbial composition through burrowing activities, excretion, and dietary composition. Desert kangaroo rats ( Dipodomys deserti ) construct burrows within loose desert sand that have microclimatic conditions different from the surrounding desert climate. In this study, we explored the effect of disturbance from kangaroo rat activities on the bacterial composition of sand. We compared the bacterial community compositions of kangaroo rat ( D. deserti ) samples, their burrows, and the proximal surface sand. The results showed that burrow sand shows higher richness and diversity of bacterial community with higher abundances of bacterial genera and genes associated with nitrogen fixation, nitrification, and urea hydrolysis compared to the surface sand. These findings suggest that kangaroo rats affect the microbial composition of their burrow environment through the introduction of food material and waste.