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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 century, sensational engineering efforts have been performed to develop new synthetic materials, and intensive studies of forces needed to deform those soft materials have examined the use of pneumatic, thermal, electrical, and chemical energy. [11][12][13] The second research stream designs low-profile, sheet-like robots, named "robotic origamis" (or "robogamis") that offer softness and reconfigurability with multiple bending degrees of freedom. [8][9][10] In robogamis, the rigid sheets are connected through soft joints, where 2D patterns can be folded into 3D structures by low profile actuations such as electrostatic forces, shape memory alloys, and pneumatic pressures. [2] Such robogamis can autonomously transform themselves into programmed shapes and perform complex tasks in unpredictable environments. Substantial progress in soft material research has produced achievements that are critical in terms of robogami techniques [2] while soft robotics and origami folding concepts have opened new applications. [9] However, soft robotics and robogamis have historically developed separately, and studies on robogamis with soft matter were unavailable or quite limited even though their integration is expected to generate substantial achievements in terms of cost, fabrication, operation, and performance. Built-in folds made of soft materials have the considerable potential to yield continuum, compliant, and configurable properties for robots.In this work, we introduce a new approach to combine these two robotic techniques by using soft paper substrates and a waterresponsive origami technique. The capillary action of sprayed water molecules is constrained by hydrophilic channels on paper, whose number and size are carefully defined by double-sided printing and the asymmetrical penetration of wax. In particular, a bilayered single sheet of paper that uses wax and water can lead to programmed deformations from different swelling and shrinking properties of the layers. A wax-water pattern on paper develops a folding actuation with a specific degree and shape and unfolding with evaporation without being mechanically manipulated by external forces or moments. The 2D sheet of paper can be controllably self-folded into various 3D structures, demonstrating self-folding actuation, low-weight object manipulation, and biomimetic locomotion through bending and relaxation. Although a couple of paper-based robotic concepts were partly proposed before, [14,15] no technique has yet emerged as a simple print-and-fold actuator powered by environmental humidity or water for comprehensive robotic functions including self-folding, Soft robotics driven by origami can fundamentally advance robotic functionalities by significantly improving continuum, compliance, and configurability. Here, a new field is proposed, "paper robotics," which is based on moistureresponsive self-folding of paper substrates into functional 3D machines using origami-inspired techniques. By properly designing a hydrophobic wax layer and a hygro-expandable hydrophilic ...

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