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Humanity's excessive production of material waste poses a critical environmental threat, and the problem is only escalating, especially in the past few decades with the rapid development of powerful electronic tools and persistent consumer desire to upgrade to the newest available technology. The poor disposability of electronics is especially an issue for the newly arising field of single-use devices and sensors, which are often used to evaluate human health and monitor environmental conditions, and for other novel applications. Though impressive in terms of function and convenience, usage of conventional electronic components in these applications would inflict an immense surge in waste and result in higher costs. This work's primary objective is to develop a cost-effective, eco-friendly, all-paper, device for single-use applications that can be easily and safely disposed of through incineration or biodegradation. All electronic components are paper-based and integrated on paper-based printed circuit boards (PCBs), innovatively providing a realistic and practical solution for green electronic platforms. In particular, a methodology is discussed for simultaneously achieving very tunable resistors (20 Ω to 285 kΩ), supercapacitors (∼3.29 mF), and electrolyte-gated field-effect transistors on and within the thickness of a single sheet of paper. Each electronic component is completely integrated into functionalized paper regions and exhibits favorable electrical activity, adjustability, flexibility, and disposability. A simple amplifier circuit is successfully demonstrated within a small area and within the thickness of a single sheet of paper, displaying component versatility and the capability for their fabrication processes to be performed in parallel for efficient and rapid development.

This work develops an all-electrical, reliable, rapid antibiotic susceptibility testing device to monitor antibiotic efficacy in bacterial biofilms that can be practically translatable to clinical settings and industrial antibiotic developments.

Pseudomonas aeruginosa is the most important opportunistic pathogen leading to serious and life-threatening infections, especially in immunocompromised patients. Because of its remarkable capacity to resist antibiotics, the selection of the right antibiotics with the exact dose for the appropriate duration is critical to effectively treat the infections and prevent antibiotic resistance. Although conventional genotypic and phenotypic antibiotic susceptibility testing (AST) methods have been dramatically advanced, they have suffered from many technical and operational issues as a generalized antibiotic stewardship program. Furthermore, given that most microbial infections are caused by their biofilms, the existing AST methods do not provide evidence-based antibiotic prescribing guidance for biofilm-based infections because the results are based on individual bacteria traditionally grown in their planktonic form. In this work, we create an innovative susceptibility testing technique for P. aeruginosa that offers clinically relevant guidelines and widely adaptable stewardship to effectively treat the infections and minimize antibiotic resistance. Our approach evaluates the antibiotic efficacy by continuously monitoring the accumulated electrical outputs from the bacterial extracellular electron transfer (EET) process in the presence of antibiotics. Our innovative paper-based culturing 3-D scaffold promotes surface-associated growth of bacterial colonies and biofilms. The platform replicates a natural habitat for P. aeruginosa where it can grow similarly to sites it infects. Our technique enables an all-electrical, real-time, easy-to-use, portable AST that can be easily translatable to clinical settings. The entire procedure takes 96 min to provide evidence-based antimicrobial prescribing guidance for biofilm-based infections.

While electrogenic, or electricity-producing, Gram-negative bacteria predominantly found in anaerobic habitats have been intensively explored, the potential of Gram-positive microbial electrogenic capability residing in a similar anoxic environment has not been considered. Because Gram-positive bacteria contain a thick non-conductive cell wall, they were previously believed to be very weak exoelectrogens. However, with the recent discovery of electrogenicity by Gram-positive pathogens and elucidation of their electron-transfer pathways, significant and accelerated attention has been given to the discovery and characterization of these pathways in the members of gut microbiota. The discovery of electrogenic bacteria present in the human gut and the understanding of their electrogenic capacity opens up possibilities of bacterial powered implantable batteries and provide a novel biosensing platform to monitor human gastrointestinal health. In this work, we characterized microbial extracellular electron-transfer capabilities and capacities of five gut bacteria: Staphylococcus aureus, Enterococcus faecalis, Streptococcus agalactiae, Lactobacillus reuteri, and Lactobacillus rhamnosus. A 21-well paper-based microbial fuel cell array with enhanced sensitivity was developed as a powerful yet simple screening method to accurately and simultaneously characterize bacterial electrogenicity. S. aureus, E. faecalis, and S. agalactiae exhibited distinct electrogenic capabilities, and their power generations were comparable to that of the well-known Gram-negative exoelectrogen, Shewanella oneidensis. Importantly, this system was used to begin a large-scale transposon screen to examine the genes involved in electrogenicity by the human pathobiont S. aureus.

A high-performance supercapacitive anode integrated into cyanobacterial biophotovoltaics allows the energy produced by the biophotovoltaics to be capacitively stored and delivered through a signifi...

The combination of electrochemically active microorganisms with miniaturized electronics has immense potential for augmenting a wide range of practical bioelectronic applications such as biosensing, bioenergy harvesting, and bio-electrosynthesis. However, a major challenge to the controllable and seamless integration of biological systems and external electronics is the fundamental mismatch in physicochemical properties and weak signal transmission between the biotic-abiotic interfaces. Here, we demonstrated an innovative method to fabricate the conductive-polymer-bacteria living electrode with a rapid and controllable 3-D printing platform and simple electrochemical polymerization techniques. The monomer precursor 3,4-ethylenedioxythiophene (EDOT) was printed into a 3-electrode electrochemical cell containing the exoelectrogen Shewanella oneidensis wild type MR-1. The monomer was in-situ electrochemically polymerized to the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT), entrapping and connecting the electrochemically active bacteria to the electrode within 35 min. Using cyclic voltammetry (CV), the living electrode showed enhanced bio-electrochemical activities, providing transformative development for bioenergy harvesters, biosensors and biomedical devices. [2020-0082]

Bacterial electrochemical activities can promote sustainable energy and environmental engineering applications. Characterizing their ability is critical for effectively adopting these technologies. Conventional studies of the electroactive bacteria are limited to insensitive, time-consuming, and labor-intensive two-electrode microbial fuel cell (MFC) techniques. Even the latest miniaturized MFC array is limited by irreproducibility and uncontrollability. In this work, we created a 4-well electrochemical sensing array with an integrated, custom-made three-electrode potentiostat to provide a controllable analytic capability without unwanted perturbations. A simple potentiostat circuit used two operational amplifiers and one resistor, allowing chronoamperometric and staircase voltammetric analyses of three well-known electroactive bacteria species: Shewanella oneidensis MR1, Pseudomonas aeruginosa PAO1, and Bacillus subtilis. Portability and disposability were emphasized by integrating all the functions into a paper substrate, which makes analyses possible at the point-of-use and in resource-limited settings without a bulky and expensive benchtop potentiostat. After use, the papertronic system was disposed of safely by incineration without posing any bacterial cytotoxic risks. This novel sensing platform creates an inexpensive, scalable, time-saving, high-performance, and user-friendly platform that facilitates the study of fundamental electrocatalytic activities of bacteria.

In this work, we enabled on-demand, long-functioning, sweat-based power generation through a wearable paper-based microbial fuel cell (MFC) using a novel spore-forming biocatalyst, Bacillus subtilis. The MFC is sustainable and survivable even in the extreme environmental conditions of human skin. B. subtilis, usually found on the skin, was able to form endospores that endure extreme dryness or nutrient limitation when sweat access was limited or unpredictable for humans at rest, offering long-term operation and stable storage. When human sweat was introduced, spore germination and gradual power generation were observed without adding nutrient germinants. Through repeated sporulation and germination depending on the sweat availability, B. subtilis provided a sustainable solution for an innovative sweat-activated power source that can result in the long-lasting vision of self-sustaining wearable electronics. Even after the 48-h operation, the device generated a maximum power density of 24 μW/cm

Considerable research efforts into the promises of electrogenic bacteria and the commercial opportunities they present are attempting to identify potential feasible applications. Metabolic electrons from the bacteria enable electricity generation sufficient to power portable or small-scale applications, while the quantifiable electric signal in a miniaturized device platform can be sensitive enough to monitor and respond to changes in environmental conditions. Nanomaterials produced by the electrogenic bacteria can offer an innovative bottom-up biosynthetic approach to synergize bacterial electron transfer and create an effective coupling at the cell-electrode interface. Furthermore, electrogenic bacteria can revolutionize the field of bioelectronics by effectively interfacing electronics with microbes through extracellular electron transfer. Here, these new directions for the electrogenic bacteria and their recent integration with micro- and nanosystems are comprehensively discussed with specific attention toward distinct applications in the field of powering, sensing, and synthesizing. Furthermore, challenges of individual applications and strategies toward potential solutions are provided to offer valuable guidelines for practical implementation. Finally, the perspective and view on how the use of electrogenic bacteria can hold immeasurable promise for the development of future electronics and their applications are presented.

The Internet of Disposable Things (IoDT) has recently emerged as a simple, low-cost, but powerful paradigm for wireless sensor networks. Stand-alone, self-sustaining IoDT devices are essential to providing effective and reliable functioning even in resource-limited environments. A stable power supply is the most critical factor in developing practical IoDT applications because their performance and deployment depend significantly on power availability. In this work, we created a micro-sized (∼62 μL) bacteria-powered biobattery for potentially powering unattended IoDT applications. The biobattery stores solid-phase microbial anodic nutrients and ionic pathways in microliter-scale chambers without an energy-intensive fluidic system, providing a relatively long-term operational capability (>8 days). We revolutionarily converted the liquid anolyte, salt bridge, and cathodic compartment into solid counterparts, increasing their densities and enabling their slow and continuous reactions. Furthermore, the solid-phase components will make the device favorable in miniaturization, integration, and operation with the solid-state IoDT applications. Our micro-biobattery produced a maximum power density of 4 μW/cm2 (0.33 mW/cm3) and current density 45 μA/cm2 (0.37 mA/cm3) after 96 h of operation while a liquid-based control device stopped generating power within 4 h.

An innovative sample-to-answer (S-to-A) polymer lab-on-a-chip (LOC) with a blood plasma separator based on asymmetric capillary force has been proposed, developed, and completely characterized for point-of-care technology (POCT) applications. A spray layer-by-layer (LbL) nanoassembly coating has been applied for the superhydrophilic surface onto the cyclic olefin copolymer (COC). Then, the developed superwetting surfaces were designed and optimized for three device applications such as lateral transportation of whole blood in the device by capillary pumping, on-chip whole blood/plasma separation with an asymmetric capillary force, and detection using a capillary-driven lateral flow colorimetric assay. Integrating three primary components of the devices, the S-to-A polymer LOC platform has been effectively confirmed for the lateral flow colorimetric assay of bovine serum albumin (BSA) from unprocessed human whole blood without an external power resource.

Electrogenic bacteria or exoelectrogens can transfer electrons to extracellular electron acceptors and thus have a wide range of applications to the ever-emerging fields of bioenergy, bioremediation, and biosensing. Standard state-of-the-art techniques for screening of electrogenic bacteria are inefficient, and often prevent rapid, high-throughput analyses. Herein, we created a simple, rapid, and straightforward papertronic 4- and 16-channel sensing platforms that is connected to a visual readout, allowing the naked eye to evaluate and quantify direct bacterial electrogenic capabilities. Our system integrated multiple 2-electrode sensing units into a signal amplifier circuit connected to light-emitting diode (LED) reporting units. The current generated from electrogenic bacteria in the sensing unit was amplified by the transistor and was transduced into LED illumination. The sensing units incorporated on the paper-based printed circuit boards (PCBs) absorbed bacteria-laden suspensions through capillary action, allowing for a rapid assessment (

Water quality monitoring is becoming an essential part of our lives as increasing human activities continue to spill unknown and unexpected contaminants into our water systems. To ensure the provision of safe and clean water to the public and the ecosystem, the development of rapid and sensitive in situ early warning systems for water toxicity monitoring is crucial. In this work, an entirely paper-based microbial fuel cell sensor utilizing freeze-dried bacteria is demonstrated as a portable and disposable water toxicity sensor. The bacterial cells were preinoculated on the anode reservoir of the device, and they were freeze-dried, making their on-site and on-demand applications possible. Upon rehydration of the bacteria with the water samples, current readings were obtained, and inhibition ratios (IRs) were calculated for different concentrations of formaldehyde as a model toxin. For 0.001, 0.01, and 0.02% of formaldehyde, IRs of 7.88, 16.08, and 23.14% were obtained, respectively. These IRs showed a very good linearity with the formaldehyde concentrations at R2 = 0.995. Additionally, the shelf life of the freeze-dried microbial fuel cell sensor was investigated. Even after 14 days of storage in the desiccator, at 4, and at −20 °C, the performance outputs compared to the new device were all at 96%.

We developed an innovative paper-based platform for high-throughput culturing, trapping, and monitoring of C. elegans. A 96-well array was readily fabricated by placing a nutrient-replenished paper substrate on a micromachined 96-well plastic frame, providing high-throughput 3D culturing environments and in situ analysis of the worms. The paper allows C. elegans to pass through the porous and aquatic paper matrix until the worms grow and reach the next developmental stages with the increased body size comparable to the paper pores. When the diameter of C. elegans becomes larger than the pore size of the paper substrate, the worms are trapped and immobilized for further high-throughput imaging and analysis. This work will offer a simple yet powerful technique for high-throughput sorting and monitoring of C. elegans at a different larval stage by controlling and choosing different pore sizes of paper. Furthermore, we developed another type of 3D culturing system by using paper-like transparent polycarbonate substrates for higher resolution imaging. The device used the multi-laminate structure of the polycarbonate layers as a scaffold to mimic the worm&rsquo, s 3D natural habitats. Since the substrate is thin, mechanically strong, and largely porous, the layered structure allowed C. elegans to move and behave freely in 3D and promoted the efficient growth of both C. elegans and their primary food, E. coli. The transparency of the structure facilitated visualization of the worms under a microscope. Development, fertility, and dynamic behavior of C. elegans in the 3D culture platform outperformed those of the standard 2D cultivation technique.

Microbial extracellular electron transfer (EET) stimulates a plethora of intellectual concepts leading to potential applications that offer environmentally sustainable advances in the fields of biofuels, wastewater treatment, bioremediation, desalination, and biosensing. Despite its vast potential and remarkable research efforts to date, bacterial electrogenicity is arguably the most underdeveloped technology used to confront the aforementioned challenges. Severe limitations are placed in the intrinsic energy and electron transfer processes of naturally occurring microorganisms. Significant boosts in this technology can be achieved with the growth of synthetic biology tools that manipulate microbial electron transfer pathways and improve their electrogenic potential. In particular, electrogenic Pseudomonas aeruginosa has been studied with the utility of its complete genome being sequenced coupled with well-established techniques for genetic manipulation. To optimize power density production, a high-throughput, rapid and highly sensitive test array for measuring the electrogenicity of hundreds of genetically engineered P. aeruginosa mutants is needed. This task is not trivial, as the accurate and parallel quantitative measurements of bacterial electrogenicity require long measurement times (~tens of days), continuous introduction of organic fuels (~tends of milliliters), architecturally complex and often inefficient devices, and labor-intensive operation. The overall objective of this work was to enable rapid ( 100-fold improvement), and high-throughput (>96 wells) characterization of bacterial electrogenicity from a single 5 μL culture suspension. This project used paper as a substratum that inherently produces favorable conditions for easy, rapid, and sensitive control of an electrogenic microbial suspension. From 95 isogenic P. aeruginosa mutant, an hmgA mutant generated the highest power density (39 μW/cm2), which is higher than that of wild-type P. aeruginosa and even the strongly electrogenic organism, Shewanella oneidensis (25 μW/cm2). In summary, this work will serve as a springboard for the development of novel paradigms for genetic networks that will help develop mutations or over-expression and synthetic biology constructs to identify genes in P. aeruginosa and other organisms that enhance electrogenic performance in microbial fuel cells (MFCs).

Biochemical energy harvesting from human sweat is arguably the most underdeveloped because of immature technologies. Nonetheless, excitement is building for scavenging power from sweat, as it is the most suitable energy source for skin-contacting wearable devices. Despite the vast potential and promise of sweat-driven power generation, the technique is limited to unstable and inefficient enzymatic catalysis, which requires fundamental breakthroughs to enable self-sustaining, long-lived power generation. Here, we for the first time demonstrate the ability to generate an innovative, practical, and longstanding power from human sweat by using the metabolisms of human skin-inhabiting bacteria, Staphylococcus epidermidis. Our sweat-powered battery was based on microbial fuel cells (MFCs), exploiting the sweat-eating bacteria as a biocatalyst to transform the chemical energy of sweat into electrical power through bacterial metabolism. A DC/DC booster circuit was connected to the stacked devices to increase the operational voltage (∼500 mV) to a maximum output of >3 V for powering a thermometer.

A high energy-density supercapacitor is currently undergoing exciting development with an entirely new kind of electric power device: a biosupercapacitor in which electric energy is simultaneously acquired and stored. This new hybrid device integrates the energy harvesting function of an electrochemical energy storage device (e.g. bio-solar cells) with the high-power operation of an internal supercapacitor. Manganese oxide/carbon nanotube/poly(3,4-ethylene dioxythiophene):polystyrene sulfonate nanocomposites on carbon cloth were developed as a novel anode for the biosupercapacitor. Cyanobacterial biofilm formed on the anode provided 3-D double-functional electrode concurrently exhibiting solar-driven energy-generating and storing features, generating maximum power and current density of $25.48\mu \mathrm{W}/\text{cm}^{2}$ and $115.81\mu \mathrm{A}/\text{cm}^{2}$ , respectively, which is the highest reported success of any existing biosupercapacitors. The 3-D dual-feature bioanode demonstrated superior capacitive behaviors, electrochemical properties, a high rate of bacterial extracellular electron transfer, and efficient mass transfer to and from the electrode, all of which led to high power generation.

We report a low cost, disposable, paper-based sensing platform for rapid identification and characterization of electroactive microorganisms in human gut. 21 spatially distinct wells of a sensor array parallely characterize microbial extracellular electron transfers of five gut microbes (Staphylococcus aureus, Enterococcus faecalis, Streptococcus agalactiae, Lactobacillus reuteri and Lactobacillus rhamnosus) in a defined, microliter culture volume by directly measuring microbial electricity generation in a novel microbial fuel cell configuration. S. aureus, E. faecalis and S. agalactiae showed distinct electrogenic capabilities. The electrogenic potential of gut microbes will be harnessed to act as a biocatalyst and produce a sufficient electrical current for practical applications.

Electroactive bacteria with in-situ biogenic palladium nanoparticles increased power density of a microbial fuel cell (MFC) by 75%. The palladium nanoparticles were biosynthesized through bioelectrochemical reduction by the bacteria and remained bound to the cell membrane, facilitating bacterial extracellular electron transfer at the cell-electrode interface. This work revolutionizes knowledge of how bacteria biosynthesize metallic nanoparticles during microbial metabolism and introduces a novel bottom-up approach to fabricate a microbial electrochemical device for renewable energy production in a more eco-friendly and cost-effective way.

Human access to safe water has become a major problem in many parts of the world as increasing human activities continue to spill contaminants into our water systems. To guarantee the protection of the public as well as the environment, a rapid and sensitive way to detect contaminants is required. In this work, a paper-based microbial fuel cell was developed to act as a portable, single-use, on-site water quality sensor. The sensor was fabricated by combining two layers of paper for a simple, low-cost, and disposable design. To facilitate the use of the sensor for on-site applications, the bacterial cells were pre-inoculated onto the device by air-drying. To eliminate any variations, the voltage generated by the microorganism before and after the air-drying process was measured and calculated as an inhibition ratio. Upon the addition of different formaldehyde concentrations (0%, 0.001%, 0.005%, and 0.02%), the inhibition ratios obtained were 5.9 &plusmn, 0.7%, 6.9 &plusmn, 0.7%, 8.2 &plusmn, 0.6%, and 10.6 &plusmn, 0.2%, respectively. The inhibition ratio showed a good linearity with the formaldehyde concentrations at R2 = 0.931. Our new sensor holds great promise in monitoring water quality as a portable, low-cost, and on-site sensor.

We demonstrate that fabricating low-cost microbial fuel cells (MFCs) can be done efficiently by using a paper substrate and origami techniques. A 3-D MFC was developed from a 2-D sheet of paper by integrating the anode, reservoir, cation exchange membrane (CEM) and air-cathode. The cell was easily formed by folding the paper along pre-defined creases. The entirely paper-based all-printed MFC developed in this work rapidly generated power with a small amount of bacteria-containing liquid through rapid adsorption and instant attachment of the bacteria cells to the anode. A graphite-polymer composite and graphite ink with activated carbon were readily applicable as novel anodic materials on paper and enhanced performance better than a conventional graphite ink or gold anode. The hydrophobic wax-based CEM was readily built with a commercially available wax printer and using heat to control how deep the wax penetrated the paper. This work will create a novel platform for paper-based power source, stepping toward batch-fabricable flexible papertronics.

A microbial fuel cell is created that uses a bacterium's natural ability to revive from dormancy to provide on-demand power for next-generation wearable applications. In adverse conditions, Bacillus subtilis responds by becoming endospores that serve as a dormant biocatalyst embedded in a skin-mountable paper-based microbial fuel cell. When activated by nutrient-rich human sweat, the germinating bacteria produce enough electricity to operate small devices, such as the calculator that we operated to test our methodology. The spore germination is artificially accelerated by nutritious germinants, which are pre-loaded on the skin-contacting bottom layer of the device, absorb the released sweat, and deliver a mixture of the dissolved germinants and sweat to the spores. When the skin-mountable device is applied to the arm of a sweating volunteer, it can generate a maximum power density of 16.6 μW/cm2 through bacterial respiratory activity. A potential risk of bacteria leakage from the device is minimized by packaging with a small pore size paper so that bacterial spores and germinated cells cannot pass through. When three serially connected devices are integrated into a single on-chip platform and energized by sweat, a significantly enhanced power density of 56.6 μW/cm2 is generated, powering an electrical calculator. After three weeks of dormant storage, the device exhibits no significant decrease in electrical output when activated by sweat. After use, the device is easily incinerated without risking bacterial infection. This work demonstrates the promising potential of the spore-forming microbial fuel cell as a disposable and long storage life power source for next-generation wearable applications.