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Background: Electrospun (e-spun) nanofibers for wound dressing have attracted wide attention due to its large specific surface area, large porosity and breathability. Compared with solution electrospinning (e-spinning), melt e-spinning is more bio-friendly without toxic solvent participation, which provides the possibility of in situ e-spinning on wounds directly. However, previously reported melt e-spinning devices were usually bulky and cumbersome due to their necessary heating unit, and different components were separated to avoid electrostatic interference. Results: In this article, we report on a self-powered hand-held melt e-spinning gun which can work without any external power supply (outdoors). The problem of electrostatic interference for this integrated device was solved by using a special high heat transfer insulation unit. The apparatus is easy and safe to operate by a single hand due to its small volume (24 × 6 × 13 cm 3) and light weight (about 450 g). Some biodegradable polymers, for example, polycaprolactone (PCL) fibers were successful e-spun onto wounds directly by using this dressing gun. Conclusions: PCL fibrous membrane has good biocompatibility and can be in situ electrospun to wound surface as a wound dressing by the portable melt e-spinning gun. Besides wound dressing, this hand-held melt e-spinning gun may be used in 3D printing and experimental teaching demonstration aids.

In this paper, we report an interesting bubble melt electrospinning (e-spinning) to produce polymer microfibers. Usually, melt e-spinning for fabricating ultrafine fibers needs “Taylor cone”, which is formed on the tip of the spinneret. The spinneret is also the bottleneck for mass production in melt e-spinning. In this work, a metal needle-free method was tried in the melt e-spinning process. The “Taylor cone” was formed on the surface of the broken polymer melt bubble, which was produced by an airflow. With the applied voltage ranging from 18 to 25 kV, the heating temperature was about 210–250 °C, and polyurethane (TPU) and polylactic acid (PLA) microfibers were successfully fabricated by this new melt e-spinning technique. During the melt e-spinning process, polymer melt jets ejected from the burst bubbles could be observed with a high-speed camera. Then, polymer microfibers could be obtained on the grounded collector. The fiber diameter ranged from 45 down to 5 μm. The results indicate that bubble melt e-spinning may be a promising method for needleless production in melt e-spinning.

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A new type of solvent-free electrospinning technique was developed to fabricate micro-fibers.

Microbatteries are indispensable to power emerging miniaturized electronics for medical, environmental, or stealth applications. However, they are usually fabricated by additive printing processes, limiting their sizes and energy densities. Here, we develop a subtractive manufacturing process by slicing assembled thin-film zinc-ion batteries into microcells in batches using optimized preintercalated MnO2 (K0.27MnO2·0.54H2O, KMO) as cathodes. The composite cathode consisting of KMO and reduced graphene oxide (rGO) delivers a high specific capacity of 323.4 mAh g–1 at 0.1 A g–1 with no capacity loss after 750 cycles at 1 A g–1. Such a high performance renders Zn//KMO/rGO solid-state microbatteries with areal energy densities of 0.244 mWh cm–2, which are comparable to those of the state of the art. This microbattery, with an area of 4 × 4 mm2 and a thickness of 0.56 mm, can be modularly arranged on a chip for a stretchable energy-supply circuit, which can be closely attached to human skin.

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