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1. A YARN-BASED BACTERIA-POWERED BATTERY FOR SMART TEXTILES

   Gao, Y. ; Liu, L. ; Choi, S. ( June 2018 , Technical digest SolidState Sensor Actuator and Microsystems Workshop)

   We report a flexible and wearable bacteria-powered battery in which four functional yarns are placed in parallel for biological energy harvesting. A current collecting yarn is sandwiched between two conductive/hydrophilic active yarns including electricity-generating bacteria while a polymer-passivated cathodic yarn is located next to one of the active yarns to form a biological fuel cell configuration. The device uses Shewanella oneidensis MR-1 as a biocatalyst to produce a maximum power of 17µW/cm3 and current density 327µA/cm3, which are enough to power small-power applications. This yarn-structured biobattery can be potentially woven or knitted into an energy storage fabric to provide a higher power for smart textiles. Furthermore, sweat generated from the human body can be a potential fuel to support bacterial viability, providing the long-term operation of the battery. 

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2. A Paper-Based Biological Solar Cell

   https://doi.org/10.1177/2472630319875403  

   Liu, Lin ; Choi, Seokheun ( September 2019 , SLAS TECHNOLOGY: Translating Life Sciences Innovation)

   A merged system incorporating paperfluidics and papertronics has recently emerged as a simple, single-use, low-cost paradigm for disposable point-of-care (POC) diagnostic applications. Stand-alone and self-sustained paper-based systems are essential to providing effective and lifesaving treatments in resource-constrained environments. Therefore, a realistic and accessible power source is required for actual paper-based POC systems as their diagnostic performance and portability rely significantly on power availability. Among many paper-based batteries and energy storage devices, paper-based microbial fuel cells have attracted much attention because bacteria can harvest electricity from any type of organic matter that is readily available in those challenging regions. However, the promise of this technology has not been translated into practical power applications because of its short power duration, which is not enough to fully operate those systems for a relatively long period. In this work, we for the first time demonstrate a simple and long-lasting paper-based biological solar cell that uses photosynthetic bacteria as biocatalysts. The bacterial photosynthesis and respiration continuously and self-sustainably generate power by converting light energy into electricity. With a highly porous and conductive anode and an innovative solid-state cathode, the biological solar cell built upon the paper substrates generated the maximum current and power density of 65 µA/cm²and 10.7 µW/cm², respectively, which are considerably greater than those of conventional micro-sized biological solar cells. Furthermore, photosynthetic bacteria in a 3-D volumetric chamber made of a stack of papers provided stable and long-lasting electricity for more than 5 h, while electrical current from the heterotrophic culture on 2-D paper dramatically decreased within several minutes.

    

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3. Sheath-run artificial muscles

   https://doi.org/10.1126/science.aaw2403  

   Jiuke Mu, Mônica Jung ( July 2019 , Science)

   Although guest-filled carbon nanotube yarns provide record performance as torsional and tensile artificial muscles, they are expensive, and only part of the muscle effectively contributes to actuation.We describe a muscle type that provides higher performance, in which the guest that drives actuation is a sheath on a twisted or coiled core that can be an inexpensive yarn. This change from guest-filled to sheath-run artificial muscles increases the maximum work capacity by factors of 1.70 to 2.15 for tensile muscles driven electrothermally or by vapor absorption. A sheath-run electrochemical muscle generates 1.98 watts per gram of average contractile power—40 times that for human muscle and 9.0 times that of the highest power alternative electrochemical muscle.Theory predicts the observed performance advantages of sheath-run muscles. 

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4. MXene‐Based Fibers, Yarns, and Fabrics for Wearable Energy Storage Devices

   https://doi.org/10.1002/adfm.202000739  

   Levitt, Ariana ; Zhang, Jizhen ; Dion, Genevieve ; Gogotsi, Yury ; Razal, Joselito M. ( May 2020 , Advanced Functional Materials)

   Textile devices have benefited from the discovery of new conductive materials and innovations in textile device design. These devices include textile‐based supercapacitors (TSCs), encompassing fiber, yarn, and fabric supercapacitors, which have demonstrated practical value in powering wearable devices. Recent review articles have highlighted the limited energy density of TSCs as an important challenge, demanding new electrode materials with higher electronic conductivity and theoretical capacitance than present materials. Ti₃C₂T_x, a member of the MXene family, is known for its metallic conductivity and high volumetric capacitance in acidic electrolytes due to its pseudocapacitive behavior. Driven by these excellent properties, recent literature has reported promising integration methods of Ti₃C₂T_xinto TSCs with significantly improved areal and volumetric capacitance compared with non‐MXene‐based TSCs. Furthermore, knitted MXene‐based TSCs demonstrated practical application of wearable energy storage devices in textiles. Herein, the techniques used to produce MXene‐based fibers, yarns, and fabrics and the progress in architecture design and performance metrics are highlighted. Challenges regarding the introduction of this new material into fiber/yarn/fabric architectures are discussed, which will inform the development of textile‐based devices beyond energy storage applications. Opportunities surrounding the development of MXene‐based fibers with tunable mechanical, electrical, and electrochemical properties are proposed, which will be the direction of future research efforts.

    

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5. From Microbial Fuel Cells to Biobatteries: Moving toward On‐Demand Micropower Generation for Small‐Scale Single‐Use Applications

   https://doi.org/10.1002/admt.201900079  

   Gao, Yang ; Mohammadifar, Maedeh ; Choi, Seokheun ( March 2019 , Advanced Materials Technologies)

   Microbial fuel cells (MFCs) that generate electricity generation from a broad diversity of biomass and organic substrates through microbial metabolism have attracted considerable research interest as an alternative clean energy technology and energy‐efficient wastewater treatment method. Despite encouraging successes and auspicious pilot‐scale experiments of the MFCs, increasing doubts about their viability for practical large‐scale applications are being raised. Low performance, expensive core parts and materials, energy‐intensive operation, and scaling bottlenecks question a sustainable development. Instead, special MFCs for low‐power battery‐reliant devices might be more applicable and potentially realizable. Such bacteria‐powered biobatteries would enable i) a truly stand‐alone device platform suitable for use in resource‐limited and remote regions, ii) simple, on‐demand power generation within a programmed period of time, and iii) a tracelessly biodegradable battery due to the use of the bacteria used for power generation. The biobattery would be an excellent power solution for small‐scale, on‐demand, single‐use, and disposable electronics. Recent progress of small‐scale MFC‐based biobatteries is critically reviewed with specific attention toward various device platforms. Furthermore, comments and outlook related to the potential directions and challenges of the biobatteries are discussed to offer inspiration to the community and induce fruitful future research.

    

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