Many emerging industry applications demand electronic systems with reliable operation at temperatures >300 °C. To date, the most promising on‐chip power sources, micro‐supercapacitors (MSCs), can only operate at temperatures up to 250 °C for a short period as limited by the vulnerability of their electrolyte frameworks at high temperatures. Here, a strategy is proposed to use liquids to lock the phase transformations of bassanite microrods for scalable on‐chip printing of interlocking ceramic frameworks with high thermal stability. The robust ceramic frameworks enable simple yet scalable fabrication of MSCs to work at 300 °C with an areal capacitance of up to >60 mF cm −2 and only ≈3% performance degradation after 1000 cycles during a test period of ≈3 h. A large‐scale MSC array, consisting of 20 cells within a footprint area of 4 cm × 8 cm, has been able to supply a power of 7.2 mW at 300 °C. These break through the present limit of 250 °C of almost all high‐temperature energy storage devices and pave the way for on‐chip MSCs for high‐temperature electronics.

Accurate evaluation of electrophysiological and morphological characteristics of the skeletal muscles is critical to establish a comprehensive assessment of the human neuromusculoskeletal function in vivo. However, current technological challenges lie in unsynchronized and unparallel operation of separate acquisition systems such as surface electromyography (sEMG) and ultrasonography. Key problem is the lack of ultrasound transparency of current electrophysiological electrodes. In this work, ultrasound (US) transparent electrode based on cellulose nanofibrils (CNF) substrate are proposed to solve the issue. US transparency of the electrodes are evaluated using a standard US phantom. The effects of nanocellulose type and ion-bond introduction on electrode performance is investigated. Simultaneous US image and sEMG signal acquisition of biceps brachii during isometric muscle contraction are studied. Reliable correlation analysis of the US and sEMG signals is realized which is rarely reported in the previous literatures. Recyclability and biodegradability of the current electrode are evaluated. The reported technology opens up new pathways to provide coupled anatomical and electrical information of the skeletal muscles, enables reliable anatomical and electrical information correlation analysis and largely simplify the sensor integration for assessment of the human neuromusculoskeletal function.

MXene is a promising energy storage material for miniaturized microbatteries and microsupercapacitors (MSCs). Despite its superior electrochemical performance, only a few studies have reported MXene-based ultrahigh-rate (>1000 mV s−1) on-paper MSCs, mainly due to the reduced electrical conductance of MXene films deposited on paper. Herein, ultrahigh-rate metal-free on-paper MSCs based on heterogeneous MXene/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS)-stack electrodes are fabricated through the combination of direct ink writing and femtosecond laser scribing. With a footprint area of only 20 mm2, the on-paper MSCs exhibit excellent high-rate capacitive behavior with an areal capacitance of 5.7 mF cm−2 and long cycle life (>95% capacitance retention after 10,000 cycles) at a high scan rate of 1000 mV s−1, outperforming most of the present on-paper MSCs. Furthermore, the heterogeneous MXene/PEDOT:PSS electrodes can interconnect individual MSCs into metal-free on-paper MSC arrays, which can also be simultaneously charged/discharged at 1000 mV s−1, showing scalable capacitive performance. The heterogeneous MXene/PEDOT:PSS stacks are a promising electrode structure for on-paper MSCs to serve as ultrafast miniaturized energy storage components for emerging paper electronics. 

Self-charging power systems (SCPSs) are envisioned as promising solutions for emerging electronics to mitigate the increasing global concern about battery waste. However, present SCPSs suffer from large form factors, unscalable fabrication, and material complexity. Herein, a type of highly stable, eco-friendly conductive inks based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) are developed for direct ink writing of multiple components in the SCPSs, including electrodes for miniaturized spacer-free triboelectric nanogenerators (TENGs) and microsupercapacitors (MSCs), and interconnects. The principle of “one ink, multiple functions” enables to almost fully print the entire SCPSs on the same paper substrate in a monolithic manner without post-integration. The monolithic fabrication significantly improves the upscaling capability for manufacturing and reduces the form factor of the entire SCPSs (a small footprint area of ≈2 cm × 3 cm and thickness of ≈1 mm). After pressing/releasing the TENGs for ≈79000 cycles, the 3-cell series-connected MSC array can be charged to 1.6 V while the 6-cell array to 3.0 V. On-paper SCPSs are promising to serve as lightweight, thin, sustainable, and low-cost power supplies. 

The rapid development of emerging electronics requires power sources with the advantages of lightweight, high efficiency, and portability. Considering the use of critical raw materials (such as Li, Co, etc.) and the increasing global concern of battery waste, self-charging power systems (SCPSs) integrating energy harvesting, power management, and energy storage devices have been envisioned as promising solutions to replace traditional batteries to avoid the use of toxic materials and the need of frequent recharging/replacement. Up to date, the reported SCPSs still hold the problem of large form factor, unscalable fabrication, noble materials, and material complexity. In our work, a highly stable and eco-friendly organic conductive ink based on poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) has been developed for monolithic fabrication on-paper SCPSs almost fully through a simple direct ink writing (DIW) process. The ink possesses multiple functions and enables to directly print almost all the key components in the SCPSs, including electrodes for triboelectric nanogenerators (TENGs, mechanical energy harvesters), electrodes for micro-supercapacitors (MSCs, energy storage devices), and interconnects, on the same paper substrate in a monolithic manner without the need for “post-integration”. The monolithic printing process exhibits excellent upscaling capability for manufacturing. In particular, the direct patterning merit of the DIW process offers great flexibility in optimizing the system performance through adjusting the cell number, electrode dimension, and thickness of the MSC arrays. By adjusting the cell numbers, the MSC arrays attain high-rate capability up to 50 V/s to match the pulsing electricity produced from the TENGs. For small-size printed SCPSs (~ 2 cm × 3 cm ×1 mm), after continuous press and release of the TENGs for ~79000 cycles, the 3-cell series-connected MSC array can be charged to 1.6 V while 6-cell array to 3.0 V. For a larger-size printed SCPS with 30 MSC cells (~ 7.5 cm × 5 cm ×0.5 mm), after charging through pressing/releasing for 10 min (nearly 1200 cycles), it can light up a LED (~ 4 W) for 5 s. The demo of successfully powering an LED device exhibited its great potential for powering various electronics. The monolithically fabricated on-paper SCPSs have great potential to serve as lightweight, thin, sustainable, eco-friendly, and low-cost power supplies for emerging electronics.

As physical topographical features suggest important effects in bone tissue engineering, an increasing amount of research on surface topographies has been carried out. In this work, melt electrowritten PCL scaffolds (mPCL) with recrystallized surfaces for osteogenic differentiation were constructed. The recrystallized grid PCL scaffolds (rPCL) show strengthened mechanical properties, retained biocompatibility, enhanced expression of alkaline phosphatase, and improved calcium mineralization compared to uncrystallized mPCL scaffolds, thereby confirming the promotion of osteogenic differentiation. In addition, lumbar vertebra-like rPCL scaffolds were successfully printed for precursor osteoblast-like cells to cellularize in the desired pattern. Importantly, the combination of recrystallization method and MEW technology introduced new function into the MEW based tissue engineering scaffolds, presenting the nano/microstructure of PCL on macroscale PCL scaffolds with enhanced osteogenic activities, which especially opens a new facile route for MEW scaffolds to broaden their applications in bone tissue engineering.

Harvesting renewable mechanical energy is envisioned as a promising and sustainable way for power generation. Many recent mechanical energy harvesters are able to produce instantaneous (pulsed) electricity with a high peak voltage of over 100 V. However, directly storing such irregular high-voltage pulse electricity remains a great challenge. The use of extra power management components can boost storage efficiency but increase system complexity. Here utilizing the conducting polymer PEDOT:PSS, high-rate metal-free micro-supercapacitor (MSC) arrays are successfully fabricated for direct high-efficiency storage of high-voltage pulse electricity. Within an area of 2.4 × 3.4 cm2 on various paper substrates, large-scale MSC arrays (comprising up to 100 cells) can be printed to deliver a working voltage window of 160 V at an ultrahigh scan rate up to 30 V s−1. The ultrahigh rate capability enables the MSC arrays to quickly capture and efficiently store the high-voltage (≈150 V) pulse electricity produced by a droplet-based electricity generator at a high efficiency of 62%, significantly higher than that (<2%) of the batteries or capacitors demonstrated in the literature. Moreover, the compact and metal-free features make these MSC arrays excellent candidates for sustainable high-performance energy storage in self-charging power systems.

Major challenges in developing implanted neural stimulation devices are the invasiveness, complexity, and cost of the implantation procedure. Here, we report an injectable, nanofibrous 2D flexible hydrogel sheet-based neural stimulation device that can be non-invasively implanted via syringe injection for optoelectrical and biochemical dual stimulation of neuron. Specifically, methacrylated gelatin (GelMA)/alginate hydrogel nanofibers were mechanically reinforced with a poly(lactide-co-ε-caprolactone) (PLCL) core by coaxial electrospinning. The lubricant hydrogel shell enabled not only injectability, but also facile incorporation of functional nanomaterials and bioactives. The nanofibers loaded with photocatatlytic g-C3N4/GO nanoparticles were capable of stimulating neural cells via blue light, with a significant 36.3 % enhancement in neurite extension. Meanwhile, the nerve growth factor (NGF) loaded nanofibers supported a sustained release of NGF with well-maintained function to biochemically stimulate neural differentiation. We have demonstrated the capability of an injectable, hydrogel nanofibrous, neural stimulation system to support neural stimulation both optoelectrically and biochemically, which represents crucial early steps in a larger effort to create a minimally invasive system for neural stimulation.

The raised demand for portable electronics in high-temperature environments (>150 °C) stimulates the search for solutions to release the temperature constraints of power supply. All-solid-state microsupercapacitors (MSCs) are envisioned as promising on-chip power supply components, but at present, nearly none of them can work at temperature over 200 °C, mainly restricted by the electrolytes which possess either low thermal stability or incompatible fabrication process with on-chip integration. In this work, we have developed a novel process to fabricate highly thermally stable ionic liquid/ceramic composite electrolytes for on-chip integrated MSCs. Remarkably, the electrolytes enable MSCs with graphene-based electrodes to operate at temperatures as high as 250 °C with a high areal capacitance (~72 mF cm⁻² at 5 mV s⁻¹) and good cycling stability (70 % capacitance retention after 1000 cycles at 1.4 mA cm⁻²).

Ever-growing various applications, especially for tissue regeneration, cause a pressing need for novel methods to functionalize melt electrowritten (MEW) microfibrous scaffolds with unique nanomaterials. Here, two novel strategies are proposed to modify MEW polycaprolactone (PCL) grids with ZnO nanoparticles (ZP) or ZnO nanoflakes (ZF) to enhance osteogenic differentiation. The calcium mineralization levels of MC3T3 osteoblasts cultured on PCL/ZP 0.1 scaffolds are ∼3.91-fold higher than those cultured on nonmodified PCL scaffolds, respectively. Due to the nanotopography mimicking bone anatomy, the PCL/ZF scaffolds (∼2.60 times higher in ALP activity compared to PCL/ZP 1 and ∼2.17 times higher in mineralization compared to PCL/ZP 0.1) achieved superior results. Moreover, the flexible feature inherited from PCL grids makes it possible for them to act as a reshapable osteogenic bioscaffold. This study provides new strategies for synthesizing nanomaterials on microscale surfaces, opening up a new route for functionalizing MEW scaffolds to fulfill the growing demand of tissue engineering.