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Paper, an inexpensive material with natural biocompatibility, non‐toxicity, and biodegradability, allows for affordable and cost‐effective substrates for unconventional advanced electronics, often called papertronics. On the other hand, polymeric elastomers have shown to be an excellent success for substrates of soft bioelectronics, providing stretchability in skin wearable technology for continuous sensing applications. Although both materials hold their unique advantageous characteristics, merging both material properties into a single electronic substrate reimagines paper‐based bioelectronics for wearable and patchable applications in biosensing, energy generation and storage, soft actuators, and more. Here, a breathable, light‐weighted, biocompatible engineered stretchable paper is reported via coaxial nonwoven microfibers for unconventional bioelectronic substrates. The stretchable papers allow intimate bioconformability without adhesive through coaxial electrospinning of a cellulose acetate polymer (sheath) and a silicone elastomer (core). The fabricated cellulose‐silicone fibers exhibit a greater percent strain than commercially available paper while retaining hydrophilicity, biocompatibility, combustibility, disposable, and other natural characteristics of paper. Moreover, the nonwoven stretchable cellulose‐silicone fibrous mat can adapt conventional printing and fabrication process for paper‐based electronics, an essential aspect of advanced bioelectronic manufacturing.

 

Single‐use paper‐based wearable devices are receiving increasing attention as a novel platform for disposable, inexpensive, noninvasive, and real‐time sweat monitoring. The bidirectional liquid transport nature of paper is the most critical barrier to effectively controlling sweat samples for reliable and accurate sweat analysis. Excessive or additionally released sweat significantly interferes with analysis when mixed with old sweat. Moreover, bio‐receptors pre‐loaded in the sensing areas can backflow and move to another sensing region generating a cross‐talk issue. This work enables effective sweat sampling and delivery in paper by facilitating unidirectional sweat transport from the skin to the sensing reservoir. The design and fabrication of a single‐layered paper membrane to achieve Janus‐type properties, which only allow moisture to flow in one direction is introduced. When the hydrophobic side of the Janus paper is placed on the skin, sweat is unidirectionally self‐pumped from the hydrophobic side to the hydrophilic sensing areas, but not the reverse. The fabrication takes two steps including easy automatic and scalable printing of hydrophobic micropatterns on paper and simple heating of the printed paper for the wax penetration. Quantitative colorimetric assessment of pH, chloride, sodium, and glucose in sweat is simultaneously performed without cross‐talk between the sensing regions.

 

Functioning ingestible capsules offer tremendous promise for a plethora of diagnostic and therapeutic applications. However, the absence of realistic and practical power solutions has greatly hindered the development of ingestible electronics. Microbial fuel cells (MFCs) hold great potential as power sources for such devices as the small intestinal environment maintains a steady internal temperature and a neutral pH. Those conditions and the constant supply of nutrient‐rich organics are a perfect environment to generate long‐lasting power. Although previous small‐scale MFCs have demonstrated many promising applications, little is known about the potential for generating power in the human gut environment. Here, this work reports the design and operation of a microbial biobattery capsule for ingestible applications. DormantBacillus subtilisendospores are a storable anodic biocatalyst that will provide on‐demand power when revived by nutrient‐rich intestinal fluids. A conductive, porous, poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate hydrogel anode enables superior electrical performance in what is the world's smallest MFC. Moreover, an oxygen‐rich cathode maintains its effective cathodic capability even in the oxygen‐deficit intestinal environment. As a proof‐of‐concept demonstration in stimulated intestinal fluid, the biobattery capsule produces a current density of 470 µA cm⁻²and a power density of 98 µW cm⁻², ensuring its practical efficacy as a novel and sole power source for ingestible applications in the small intestine.

 

Electronic waste is a global issue brought about by the short lifespan of electronics. Viable methods to relieve the inundated disposal system by repurposing the enormous amount of electronic waste remain elusive. Inspired by the need for sustainable solutions, this study resulted in a multifaceted approach to upcycling compact discs. The once-ubiquitous plates can be transformed into stretchable and flexible biosensors. Our experiments and advanced prototypes show that effective, innovative biosensors can be developed at a low-cost. An affordable craft-based mechanical cutter allows pre-determined patterns to be scored on the recycled metal, an essential first step for producing stretchable, wearable electronics. The active metal harvested from the compact discs was inert, cytocompatible, and capable of vital biopotential measurements. Additional studies examined the material’s resistive emittance, temperature sensing, real-time metabolite monitoring performance, and moisture-triggered transience. This sustainable approach for upcycling electronic waste provides an advantageous research-based waste stream that does not require cutting-edge microfabrication facilities, expensive materials, and high-caliber engineering skills.

 

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.

 

Bacteria‐powered biobatteries using multiple microbial species under well‐mixed conditions demonstrate a temporary performance enhancement through their cooperative interaction, where one species produces a resource that another species needs but cannot synthesize. Despite excitement about the artificial microbial consortium, those mixed populations cannot be robust to environmental changes and have difficulty generating long‐lasting power because individual species compete with their neighbors for space and resources. In nature, microbial communities are organized spatially as multiple species are separated by a few hundred micrometers to balance their interaction and competition. However, it has been challenging to define a microscale spatial microbial structure in miniature biobatteries. Here, an innovative technique to design microscale spatial structures with microbial multispecies for significant improvement of the biobattery performance is demonstrated. A solid‐state layer‐by‐layer agar‐based culture platform is proposed, where individual microcolonies separately confined in microscale agar layers form a 3‐D spatial structure allowing for the exchange of metabolites without physical contact between the individual species. The optimized microbial co‐cultures are determined from selected hypothesis‐driven naturally‐occurring bacteria. Vertically and horizontally structured 3‐D microbial communities in solid‐state agar‐based microcompartments demonstrate the practicability of the biobattery, generating longer and greater power in a more self‐sustaining manner than monocultures and other mixed populations.

 

Biofuel cells have been in the spotlight for the past century because of their potential and promise as a unique platform for sustainable energy harvesting from the human body and the environment. Because biofuel cells are typically developed in a small platform serving as a primary battery with limited fuel or as a rechargeable battery with repeated refueling, they have been interchangeably named biobatteries. Despite continuous advancements and creative proof-of-concept, however, the technique has been mired in its infancy for the past 100 years, which has provoked increasing doubts about its commercial viability. Low performance, instability, difficulties in operation, and unreliable and inconsistent power generation question the sustainable development of biofuel cells. However, the advancement in bioelectrocatalysis revolutionizes the electricity-producing capability of biofuel cells, promising an attractive, practical technique for specific applications. This perspective article will identify the misconceptions about biofuel cells that have led us in the wrong development direction and revisit their potential applications that can be realizable soon. Then, it will discuss the critical challenges that need to be immediately addressed for the commercialization of the selected applications. Finally, potential solutions will be provided. The article is intended to inspire the community so that fruitful commercial products can be developed soon.