Biofilms are severe operational and economic burdens across water, energy, medical, manufacturing, and food sectors, yet real-time detection is not available. Electrochemical biofilm sensing (EBS) represents a promising monitoring technology that utilizes charge-transfer and capacitive phenomena at electrode interfaces. This innovative approach allows continuous, label-free evaluation under industrial conditions, thereby enhancing the reliability and efficiency of the monitoring process. This perspective summarizes recent advances in EBS techniques, identifies industrial needs, and outlines the required work for EBS standardization. In addition, we highlight microbial, standardization, and engineering challenges that must be addressed for successful EBS adoption in industrial solutions.

Biofilms represent complex microbial communities that pose significant challenges across healthcare, environmental, and industrial sectors because of their resistance to antibiotics and persistence on surfaces. Electrochemical sensors have garnered attention among emerging detection techniques because of their rapid, label-free, and real-time biofilm monitoring capabilities. The performance of these sensors, however, critically hinges on the choice of electrode material, which governs sensitivity, selectivity, stability, and biocompatibility. This review comprehensively explores the evolution and application of electrode materials used in electrochemical biofilm detection, ranging from traditional noble metals such as gold and platinum to advanced carbon-based materials, polymers, nanostructured composites, and laser-induced graphene. Each material’s physicochemical properties, modification strategies, and suitability for specific biofilm types are evaluated in terms of detection efficiency and real-world applicability. Special emphasis is placed on nanomaterial-functionalized platforms and emerging low-cost, flexible electrodes for point-of-care diagnostics and environmental sensing. By correlating material selection with biofilm detection performance, this review highlights current challenges, such as electrode fouling and signal drift, and proposes future directions, including multifunctional sensors and wireless integration. Ultimately, this work underscores the pivotal role of material innovation in advancing electrochemical technologies for precise and robust biofilm monitoring.

Studying biofilms in a microgravity environment currently relies on one of two scenarios, collecting planktonic aggregates in rotating wall vessels or performing experiments in the microgravity environment of space on the International Space Station. While informative techniques, both have their limitations when studying surfaceattached microbial communities. A simulated microgravity biofilm reactor (SMBR) was developed to study biofilms in microgravity, coupled with the integration of microfabricated sensors for internal system monitoring. The establishment of simulated microgravity was demonstrated through computational fluid dynamic modelling revealing low fluid shear stress conditions (<1 mPa) throughout the reactor and on the wall surface. Microfabricated resistance temperature devices integrated in the reactor walls confirmed the capability for continuous sensor measurements during operation with the ability to perform traditional microbiology analyses on the sensor surface following an experiment. Microbiological analyses established that there were no significant differences in biofilm growth between sensor and wall surfaces within the reactor. With the integration of defined sampling surfaces, the SMBR allows for in-depth biofilm analysis in a repeatable and accessible manner allowing for a greater understanding of the effects of microgravity on biofilm.

This paper presents the development, production, and application of a 3D-printed microfluidic device designed to measure the viscoelastic recovery time of cartilage cells, chondrocytes. Bovine chondrocytes were imaged using a confocal microscope while compressed by a movable glass plate. Their recovery was monitored by tracking their projected area over time, converting it into a linear strain, and fitting it to a Burgers mechanical model. Strains ranging from 10% to 60% were applied to the cells, and model parameters, including the viscoelastic recovery time, were derived. We found that cells subjected to strains greater than 40% exhibited radially-symmetric deformations. This radially-symmetric deformation, possibly cell blebbing, was observed as a short-term effect, with the cell fully recovering its initial shape. Non-blebbing and blebbing chondrocytes exhibited viscoelastic recovery times of 42 s and 38 s, respectively. While the recovery time did not depend on the magnitude of applied strain, the measured permanent strain increased with higher applied strain magnitude. Overall, this study demonstrates the use of a new, low-cost 3D-printed microfluidic device in combination with advanced microscopy for characterizing the viscoelastic properties of cells.

Monitoring river water quality is crucial for assessing and maintaining the health of local ecosystems, particularly in agriculture and livestock management. This is especially true in arid regions like Montana, where limited water sources necessitate sustainable water management practices to support farming and ranching. In these areas, rivers and streams often serve as key water supplies for irrigation, livestock, and even drinking water, making it essential to monitor and manage water quality effectively. The U.S. Geological Survey (USGS) autonomously measures water temperature, conductivity, and flow rates, among others, to assess river conditions, but there is currently no assessment of microbial concentration. Manual field sampling and laboratory analysis are the standard protocols to analyze dynamic changes, with results often impeded by high costs for labor and required wet-chemical laboratory settings. Also, localized sampling minimizes the spatial resolution of environmental changes. There is a need for an autonomous, low-cost water monitoring system that can be integrated into a sentinel remote sensing unit for biofilm and pathogen detection in harsh environments. This study reports the two-month deployment of microfabricated sensor arrays to measure temperature, conductivity, and electrochemical impedance spectroscopy (EIS) in the Clark Fork River at USGS site 12323800 near Galen, Montana. Two sensor arrays connected to an additively manufactured waterproof housing were submerged in the river, and data was collected with a Data Acquistion Station (DAQ) described below. Data from each sensor was collected every 15 minutes for the whole duration of the installment and stored locally. A Data Acquisition Station (DAQ) was developed using a single-board computer to control an on-site impedance spectroscope and log sensor data. The DAQ supports data retrieval via Wi-Fi and LoRa interfaces. The Wi-Fi interface is designed for transferring large datasets over short distances, with an effective range of approximately 300 feet (about 91 meters) from the base station. In contrast, the LoRa interface transmits status updates and control data, typically a few bytes in size, over distances up to 20 miles (approximately 32 kilometers) in rural areas. The DAQ features an HTTPS-secured RESTful API, enabling seamless integration into an overarching network infrastructure and providing point-to-point access. Future deployments plan to use the LoRa interface. The sensor arrays were made of thin film Au structures on borosilicate glass, which were fabricated using standard evaporation, lithography, and wet chemical etching techniques. The resistive temperature device (RTD) and ring electrode conductivity sensors were added to the sensor array in part to compare to data from the USGS probe located at the same site. The EIS sensor consisted of 50 pairs of 10 µm interdigitated electrodes (IDE) with 15 µm gaps. To enhance sensitivity and stability, one side of the EIS IDE was modified with poly (4-styrenesulfonic acid) doped with pyrrole, termed PPy:PSS. Impedance sweeps of 100 mV from 100 Hz to 100 kHz were recorded for the Eis sensor. The temperature and conductivity data from these sensors were compared to those generated by USGS, and the general daily trends were in good agreement. The discrepancy in the magnitude of the measured values indicates that further work should be done to characterize the performance of these sensors. EIS data from each sweep was fit to a Randles circuit with a constant phase element (CPE) to describe interface processes. The CPE magnitude was tracked over deployment and gradually increased, indicating biofilm growth on the sensor. After 600 hours, the value saturated, suggesting a complete biofilm layer had formed. Our results provide new insights into water biology fluctuations and demonstrate the potential of EIS for real-time monitoring applications.

The demand for maple syrup is increasing, and producers must improve efficiency to maintain high-quality products at a low cost. To meet transparency, density, color, and aroma standards, quality control systems are established throughout boiling processes. However, microbial growth in the harvesting infrastructure throughout the sugaring season has been a significant challenge, as biofilms reduce sap flow rates or cause clogging of sap lines. Microbial growth also degrades the product's quality by changing the syrup's color, taste, and viscosity. Therefore, smart farming is an essential solution that can bridge the gap between microbial growth monitoring and maple syrup quality. Wireless Sensor Networks in maple forests, also known as sugar bushes, are vital for monitoring processes such as sap harvesting using individual sensor nodes that send current biogeochemical information to a field station. A biofilm sensor is needed to indicate biofilm formation in real time. This presentation introduces a microfabricated electrochemical impedance spectroscopy sensor (EIS) tailored to measure biofilm formation in sap infrastructure during the harvesting season, defined by temperature fluctuations between -10 and 20 ˚C. Impedance spectroscopy sensors were fabricated using standard evaporation, lithography, and wet chemical etching techniques. To increase the sensitivity of biofilm formation, interdigitated electrodes with a 15 µm gap between two electrodes were utilized, and 50 gold electrode pairs were implemented on a borosilicate glass wafer. Diced EIS dies were integrated into an additively manufactured housing that allowed electrochemical measurements in maple sap in the laboratory or sugar bush. To test the efficacy of the EIS sensor, a Pseudomonas Sp. strain was extracted from maple sap harvested in 2023 at the Michigan State University Upper Peninsula Forestry Innovation Center and grown at room temperature. Sterile sap was filled into the flow cell and inoculated with microorganisms after 4 h. All experiments were performed in triplicates, and abiotic controls followed the same procedure minus the injection of cell culture enrichments. Impedance data were captured every 30 minutes for 7 days, and impedance changes to the abiotic signal were characterized at defined frequencies. After 1 hour, an impedance change of 15% was observed. The impedance magnitude decreased over 7 days, indicating biofilm maturation. Biofilm growth on the EIS surface was confirmed with confocal microscopy. An impedance increase was observed in some cases, indicating biofilm detachment. Additionally, a model has been developed that relates the impedance response of maple sap to the required outdoor temperature range of -10 and 20 ˚C. Ultimately, this paper shows EIS as a valuable tool to characterize biofilm formation caused by maple sap.

Biofilms are self-organized communities of microorganisms that are encased in an extracellular polymeric matrix and often found attached to surfaces. Biofilms are widely present on Earth, often found in diverse and sometimes extreme environments. These microbial communities have been described as recalcitrant or protective when facing adversity and environmental exposures. On the International Space Station, biofilms were found in human-inhabited environments on a multitude of hardware surfaces. Moreover, studies have identified phenotypic and genetic changes in the microorganisms under microgravity conditions including changes in microbe surface colonization and pathogenicity traits. Lack of consistent research in microgravity-grown biofilms can lead to deficient understanding of altered microbial behavior in space. This could subsequently create problems in engineered systems or negatively impact human health on crewed spaceflights. It is especially relevant to long-term and remote space missions that will lack resupply and service. Conversely, biofilms are also known to benefit plant growth and are essential for human health (i.e., gut microbiome). Eventually, biofilms may be used to supply metabolic pathways that produce organic and inorganic components useful to sustaining life on celestial bodies beyond Earth. This article will explore what is currently known about biofilms in space and will identify gaps in the aerospace industry's knowledge that should be filled in order to mitigate or to leverage biofilms to the advantage of spaceflight.

Microbial biofilm contamination is a widespread problem that requires precise and prompt detection techniques to effectively control its growth. Microfabricated electrochemical impedance spectroscopy (EIS) biosensors offer promise as a tool for early biofilm detection and monitoring of elimination. This study utilized a custom flow cell system with integrated sensors to make real-time impedance measurements of biofilm growth under flow conditions, which were correlated with confocal laser scanning microscopy (CLSM) imaging. Biofilm growth on EIS biosensors in basic aqueous growth media (tryptic soy broth, TSB) and an oil-water emulsion (metalworking fluid, MWF) attenuated in a sigmoidal decay pattern, which lead to an & SIM;22-25% decrease in impedance after 24 Hrs. Subsequent treatment of established biofilms increased the impedance by & SIM;14% and & SIM;41% in TSB and MWF, respectively. In the presence of furanone C-30, a quorum-sensing inhibitor (QSI), impedance remained unchanged from the initial time point for 18 Hrs in TSB and 72 Hrs in MWF. Biofilm changes enumerated from CLSM imaging corroborated impedance measurements, with treatment significantly reducing biofilm. Overall, these results support the application of microfabricated EIS biosensors for evaluating the growth and dispersal of biofilm in situ and demonstrate potential for use in industrial settings.One-Sentence Summary This study demonstrates the use of microfabricated electrochemical impedance spectroscopy (EIS) biosensors for real-time monitoring and treatment evaluation of biofilm growth, offering valuable insights for biofilm control in industrial settings. Graphical Abstract The accurate real-time detection of biofilm growth and removal is effectively demonstrated through the combination of impedance biosensors and high-resolution confocal laser scanning microscopy.

Biofilm contamination is a widespread issue that can occur anywhere when organisms attach to surfaces in the presence of water. In industrial environments, formation of biofilms can lead to component failure, material degradation, and biofouling or spoilage, which collectively come with significant economic costs. Microfabricated electrochemical impedance spectroscopy (EIS) sensors have emerged as a promising tool for monitoring biofilm as EIS sensors capture information about biofilm growth autonomously in real-time; however, sensors suffer from drift, and the technique lacks temporal interpretation of dynamic biofilm processes. In this work, microfabricated sensors featuring gold micro-interdigitated electrodes (μIDEs) were modified with an electrically conductive polymer layer resulting in EIS measurement variability that was significantly reduced compared to unmodified sensors, and enabled highly stable, time-resolved EIS measurements. EIS characterization of Pseudomonas aeruginosa biofilm in parallel with high-resolution confocal laser scanning microscopy (CLSM) was performed using a novel 3D-printed flow cell system, resulting in distinct changes to EIS data corresponding with consistent biofilm growth. We have shown that EIS microsensors can detect four stages of biofilm: (i) initial biofilm attachment to the sensor substrate, (ii) early-stage irreversible biofilm proliferation characterized by sparse biofilm coverage, (iii) mature biofilm detection characterized by uniform biofilm coverage, and (iv) changes due to detachment and regrowth of biofilm.

During the growth of a polycrystalline ice lattice, microorganisms partition into veins, forming an ice vein network highly concentrated in salts and microbial cells. We used microfabricated electrochemical impedance spectroscopy (EIS) sensors to determine the effect of microorganisms on the electrochemical properties of ice. Solutions analyzed consisted of a 176 μ S cm −1 conductivity solution, fluorescent beads, and Escherichia coli HB101-GFP to model biotic organisms. Impedance spectroscopy data were collected at −10 °C, −20 °C, and −25 °C within either ice veins or ice grains (i.e., no veins) spanning the sensors. After freezing, the fluorescent beads and E. coli were partitioned into the ice veins. The corresponding impedance data were discernibly different in the presence of ice veins and microbial impurities. The presence of microbial cells in ice veins was evident by decreased electrical characteristics (electrode polarization between electrode and ice matrix) relative to solid ice grains. Further, this electrochemical behavior was reversed in all bead-doped solutions, indicating that microbial processes influence sensor response. Linear mixed-effects models empirically corroborated the differences in polarization associated with the presence and absence of microbial cells in ice. We show that EIS has the potential to detect microbes in ice and differentiate between veins and solid grains.

Electrically conductive carbon powders are commonly used as filler materials in polymers to create elec-trically semi-conductive composite materials for use in battery electrodes and anti-static applications. Current methods for characterizing the conductivity of these powders use two pistons to compress the powders. Two-piston methods are known to underestimate conductivity. This study develops a guard-electrode method based on ASTM D257 to better characterize the bulk conductivity and impedance spec-tra of electrically conductive powders. The conductivity and impedance spectra of a highly conductive powder (copper powder) and a low conductivity powder (cellulose) were used to bound the conductivity of carbon black, graphite, and biochar. Powders were measured through a full range of compression with both the two-piston and the guard-electrode method. In all cases, measurements using the guard-electrode method have higher conductivity and lower impedance than the same powders measured using the two-piston method. The grain conductivity of the particles is obtained through fitting the relationship of conductivity versus packing fraction using the GEM equation. The guard-electrode method is shown to be more similar to established conductivity values as measured via a four-probe technique for copper and graphite then the two-piston method. (c) 2021 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

Electrochemical techniques such as impedance spectroscopy offer a non-invasive approach to monitor microorganisms in natural and engineered environments. Here, we present data on the use of microfabricated impedance spectroscopy sensors for the detection of microbes in icy environments. Under controlled laboratory settings, the effects of different cell concentrations of the Antarctic isolate Flavobacterium sp. ANT 11 on impedance spectroscopy was investigated at ambient temperature (22°C) and -10°C. Results show that varying cell concentrations of the bacterial isolate generate unique spectral responses that vary with temperature. Subsequent tests on the performance of microfabricated impedance sensors on natural microbial communities in icy environments in the Beartooth Mountains, WY, USA, confirmed laboratory findings. Different environmental samples at varying microbial concentrations in liquid, semi-frozen (slushy), or frozen states generated discrete impedance spectra. While caution is advised to generalize these results due to the potential contribution of unknown environmental variables, our data provide fertile territory for research in cryo-microbiology, as information on the applicability of impedance spectroscopy under frozen conditions is limited. [2020-0150]

Significant improvements are being made in 3D printed microfluidics. 3D printing of microfluidic prototypes gained importance due to the fabrication flexibility compared to conventional techniques. Applications using these devices often require optical access to internal channels but even clear resins create translucent channels due to surface roughness and imperfections. This paper describes a 3D printing approach to form fluidic channels directly onto glass substrates that allows optical access to fluidic channels without distortion from 3D printing material. The glass substrate is itself a part of the flow channel which allows optical transparency. Micro-fabricated conductivity and impedance spectroscopy sensors were fabricated on glass substrates and placed in a custom made 3D printer build plate before fluidic structures are directly printed on top of the sensors. The effects on sensor performance and properties were evaluated using co-linear four-point probe resistance measurements, Raman spectroscopy, and impedance spectroscopy. It was shown that no resin or other chemicals are left behind from the printing procedure and sensor performance was unaffected. A proof of concept impedance-conductivity sensor was integrated with a 3D printed flow channel and shown to work as both conductivity and bacterial cells detection sensor.

This study investigated the rehydration of active dried yeast and the impact of temperature and wort density on the strength and stiffness of individual cells using a microelectromechanical system. Dried yeast was rehydrated using a variety of methods, including direct pitching into wort (13.6 degrees P) at 12, 22 and 30 degrees C, as well as propagation using YEPD media (4.2 degrees P). Cell viability was found to broadly correlate with measurement of cell strength and stiffness. Both wort density and temperature affected viability and physical characteristics of the cells after 1 h of rehydration. Yeast cells rehydrated at low temperature and high wort density burst at a lower force (0.26 +/- 0.02 mu N) than cells rehydrated using high temperature and low density media (0.50 +/- 0.10 mu N). Cells rehydrated at higher temperatures or using low density media showed no significant difference in strength and stiffness when compared with high viability, actively fermenting yeast. Changes in yeast physiology, owing to stress responses, may contribute to the observed differences in mechanical properties. These findings have application in brewery design, as pumping, centrifugation, storage and associated shear impart mechanical stress upon yeast cells. (C) 2018 The Institute of Brewing & Distilling

Micro-fabricated sensors enable the study of chemical and physical dynamics in aqueous environments such as rivers, lakes or oceans at low cost. Sensors must work reliably in these environments, which include both biological and chemical challenges. However, sensor thin films have not been studied in detail for aqueous applications, and more specifically how biotic interactions may change sensor material properties. In this study, the long-term effects of biofilm formation on the properties of aluminum (electric conductor) and a-SixNy:H (insulating material) were investigated. Material degradation caused by Escherichia coli K12 biofilm growth was determined by electrical sheet resistance measurements (collinear four-point-probe) and Fourier-transform infrared spectroscopy (FTIR) absorption spectra over a time period of 7 weeks. Changes of the surface topography were tested using scanning electron microscopy (SEM) and white light interferometry. Aluminum was found to be heavily degraded at three weeks, whereas a-SixNy:H was inert during the entire investigation period. As differences between thin film sensor materials are evident, more detailed investigations including a broader range of materials should be explored.

Biocomposites are potentially sustainable alternatives to traditional plastics and composites for which recycling is challenging. We assess four agricultural residue fibers (AF) in biocomposites with poly-(hydroxybutyrate-cohydroxyvalerate) (PHBV): (i) hollow stem wheat, (ii) solid stem wheat, and (iii) barley as regionally significant food crop residues compared to (iv) hemp residue as an industrially-relevant control. AF (0 wt.%, 10 wt.%, 20 wt.%, 30 wt.%) were compounded with PHBV using two compatibilization treatments: (i) a silane coupling agent vapor deposited at room temperature and (ii) PHBV grafted to the fibers using reactive extrusion (gPHBV). Flexural modulus and ultimate strength were used to evaluate the impact of fiber fraction and treatments. Modulus increased with increasing fiber fraction, with 30% treated hemp composites having the highest modulus and strength. Hollow stem wheat was most comparable to hemp. The mechanical properties of the different AF-composites occupy a similar application space, indicating potential for robust composite processing using AF.

A MEMS squeezer able to compress single living cells underwater until rupture was designed and tested. The relatively large motion range of the device in aqueous media (~2.5 µm) allows provoking cell disruption while measuring cell mechanical properties before and after membrane rupture. An AC driven electrothermal micro actuator with mechanical amplification pressed single cells against a reference back spring. Deformations of the cell and the reference spring were measured with nanoscale resolution using optical Fourier transform techniques. The motion of the reference spring divided by the cell deformation provides the cell stiffness relative to the reference spring constant. An abrupt change in the cell stiffness and the appearance of cracks indicated the cell wall rupture force was reached. A total of 22 baker’s yeast cells (Saccharomyces cerevisiae) were squeezed with the micro device. The average force necessary to rupture the cell membrane was 0.47  ±  0.1 µN. Before rupture the cells had an average stiffness of 9.3  ±  3.1 N m−1; the post-rupture stiffness dropped to 0.94  ±  0.57 N m−1. Cell hysteresis was also measured: cells squeezed and released before reaching the rupture force showed residual deformations below 100 nm, while cells squeezed past the rupture force and then released showed residual deformations between 490 and 990 nm.

The mechanical properties of individual yeast cells were measured using microelectromechanical systems (MEMS). Samples were taken throughout two controlled fermentations conducted as per ASBC Yeast-14: one utilized ale yeast (Saccharomyces cerevisiae, "red ale") and the other utilized a lager strain (S. pastorianus, "SMA"). At least five lager and five ale cells were tested at each fermentation phase (start, middle, and end). Cell compression was induced by a MEMS squeezer, and displacement measurements were taken using optical microphotographs. The failure of each cell was similar; the cell would undergo minor deformation until visible rupture occurred, followed by significant cell shrinkage. Across all fermentation phases ale cells ruptured under an average force of 0.28 +/- 0.05 mu IN, whereas lager cells ruptured at 0.47 +/- 0.10 mu N. The average stiffness at the midpoint of fermentation was found to be 4.8 +/- 1.0 and 5.3 +/- 0.9 mu N/mu m for ale and lager cells, respectively. The use of MEMS technology to study physical characteristics of brewing yeast during fermentation has not previously been attempted (to the authors' knowledge). This study may assist brewers in the selection of process parameters to improve yeast health and in the design of novel yeast handling technologies.

The goal of this study was to measure the mechanical stiffness of individual cells and to observe changes due to the application of repeated cell mechanical loads. 28 single baker’s yeast cells (Saccharomyces cerevisiae) were fatigue tested and had their stiffness measured during repetitive loading cycles performed by a MEMS squeezer in aqueous media. Electrothermal micro-actuators compressed individual cells against a reference back spring; cell and spring motions were measured using a FFT image analysis technique with ~10 nm resolution. Cell stiffness was calculated based on measurements of cell elongation vs. applied force which resulted in stiffness values in the 2–10 N/m range. The effect of increased force was studied for cells mechanically cycled 37 times. Cell stiffness decreased as the force and the cycle number increased. After 37 loading cycles (~4 min), forces of 0.24, 0.29, 0.31, and 0.33 μN caused stiffness drops of 5%, 13%, 31% and 41% respectively. Cells force was then set to 0.29 μN and cells were tested over longer runs of 118 and 268 cycles. After 118 cycles (~12 min) cells experienced an average stiffness drop of 68%. After 268 cycles (~25 min) cells had a stiffness drop of 77%, and appeared to reach a stiffness plateau of 20–25% of the initial stiffness after approximately 200 cycles.