Recently, several reports have demonstrated that a moving droplet of seawater or ionic solution over monolayer graphene produces an electric power of about 19 nW, and this has been suggested to be a result of the pseudocapacitive effect between graphene and the liquid droplet. Here, we show that the change in the triboelectrification-induced pseudocapacitance between the water droplet and monolayer graphene on polytetrafluoroethylene (PTFE) results in a large power output of about 1.9 μW, which is about 100 times larger than that presented in previous research. During the graphene transfer process, a very strong negative triboelectric potential is generated on the surface of the PTFE. Positive and negative charge accumulation, respectively, occurs on the bottom and the top surfaces of graphene due to the triboelectric potential, and the negative charges that accumulate on the top surface of graphene are driven forward by the moving droplet, charging and discharging at the front and rear of the droplet.

Harvesting human-motion energy for power-integrated wearable electronics could be a promising way to extend the battery-operation time of small low-power-consumption electronics such as various sensors. For this purpose, a fully stretchable triboelectric nanogenerator (S-TENG) that has been fabricated with knitted fabrics and has been integrated with the directly available materials and techniques of the textile industry is introduced. This device has been adapted to cloth movement and can generate electricity under compression and stretching. We investigated plain-, double-, and rib-fabric structures and analyzed their potentials for textile-based energy harvesting. The superior stretchable property of the rib-knitted fabric contributed to a dramatic enhancement of the triboelectric power-generation performance owing to the increased contact surface. The present study shows that, under stretching motions of up to 30%, the S-TENG generates a maximum voltage and a current of 23.50 V and 1.05 μA, respectively, depending on the fabric structures. Under compressions at 3.3 Hz, the S-TENG generated a constant average root-mean square power of up to 60 μW. The results of this work show the feasibility of a cloth-integrated and industrial-ready TENG for the harvesting of energy from human biomechanical movements in cloth and garments.

Three-dimensional (3D), submillimeter-scale constructs of neural cells, known as cortical spheroids, are of rapidly growing importance in biological research because these systems reproduce complex features of the brain in vitro. Despite their great potential for studies of neurodevelopment and neurological disease modeling, 3D living objects cannot be studied easily using conventional approaches to neuromodulation, sensing, and manipulation. Here, we introduce classes of microfabricated 3D frameworks as compliant, multifunctional neural interfaces to spheroids and to assembloids. Electrical, optical, chemical, and thermal interfaces to cortical spheroids demonstrate some of the capabilities. Complex architectures and high-resolution features highlight the design versatility. Detailed studies of the spreading of coordinated bursting events across the surface of an isolated cortical spheroid and of the cascade of processes associated with formation and regrowth of bridging tissues across a pair of such spheroids represent two of the many opportunities in basic neuroscience research enabled by these platforms.

Multi-phase rotation-type triboelectric nanogenerators generate an almost constant direct current output, which overcomes the typical limitation of triboelectric nanogenerators.

Temporary postoperative cardiac pacing requires devices with percutaneous leads and external wired power and control systems. This hardware introduces risks for infection, limitations on patient mobility, and requirements for surgical extraction procedures. Bioresorbable pacemakers mitigate some of these disadvantages, but they demand pairing with external, wired systems and secondary mechanisms for control. We present a transient closed-loop system that combines a time-synchronized, wireless network of skin-integrated devices with an advanced bioresorbable pacemaker to control cardiac rhythms, track cardiopulmonary status, provide multihaptic feedback, and enable transient operation with minimal patient burden. The result provides a range of autonomous, rate-adaptive cardiac pacing capabilities, as demonstrated in rat, canine, and human heart studies. This work establishes an engineering framework for closed-loop temporary electrotherapy using wirelessly linked, body-integrated bioelectronic devices.

Figure 2. a) Schematic diagram showing the fabrication process of fiber-based TENG. SEM images of b) a CNT-coated cotton thread and c) (PTFE) and CNT-coated cotton thread. d) Real image of fiber-based TENG. f) Output current-time curve of a fiber-based TENG with stimulation strains of 0%, 0.54%, 1.08%, 1.61%, and 2.15% at a constant frequency of 5 Hz. g) Output current-time curve of a fiber-based TENG with stimulation frequency of 1.3, 2, 3, 4, and 5 Hz at a constant strain of 2.15 Hz. h) Durability test of fiber-based TENG for 5 h (≈90 000 cycles). Reproduced with permission. [33]

No abstract

Paper‐based electronics has attracted growing interest owing to many advantages of papers including low‐cost, abundance, flexibility, biocompatibility, and environmental friendliness. Despite recent progress in paper electronics, however, development of a high‐performance paper‐based triboelectric nanogenerator (TENG), which is a power‐generating device that converts mechanical energy into electric energy by coupling triboelectrification and electrostatic induction, remains a challenge mainly due to weak electron‐donating tendency of cellulose‐based papers. In this work, highly conductive ferroelectric cellulose composite papers containing silver nanowires and BaTiO3 nanoparticles are fabricated, and their successful application for realizing a large‐area TENG with enhanced electrical output performance is demonstrated. It is found that triboelectric charge generation on the ferroelectric cellulose composite paper can be promoted by simple poling treatment, which significantly enhances TENG performance. The ferroelectric cellulose composite paper–based TENG exhibits an electrical output performance that surpasses those of aluminum‐based and pristine cellulose–based TENGs by more than two times, as well as outstanding output stability without a noticeable degradation in performance during 10 000 cycles of a repeated pushing test. The work demonstrates the great potential of multifunctional cellulose‐based papers for TENG and other self‐powered electronic applications.