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In this paper, a top-down method is used to partially hydrolyze leather to achieve a leather-based gel electrolyte, and successfully develop a leather-based all-in-one configured flexible supercapacitor. The hierarchical structure of collagen fibers effectively solves the interface problem of flexible supercapacitors, and at the same time endows the gel electrolyte with degradability and reproducibility.

The ability of perceiving external pressures and conducting corresponding signals is one of the important functions of flexible electronics, which has been widely studied in electronic skin, prosthetics, robotics, healthcare, human-machine interfaces, etc. Pressure sensor should not be limited to the detection of unidirectional pressure. Here, a leather-based electronic pressure sensor and corresponding arrays with bidirectional sensing capability are demonstrated. The sensor/arrays consisting of two pieces of stacked leather both modified with acidified carbon nanotubes (a-CNTs) can achieve multi-level response to pressure over a broad working range and sense pulling force opposite to pressure. With polyurethane mixed with ferriferrous oxide (Fe3O4) powder being applied to their upper surface, the resistive sensor/individual units of arrays can also detect the magnetic field because of the contactless pulling force generated by the magnetized Fe3O4. Being able to sense pressure, pulling force and magnetic field, the leather-based electronic bidirectional pressure sensor and corresponding arrays with good performance not only exhibit potential for mass production and their broad application prospects, but also provide a new insight for the development of flexible electronics.

Printing methods are potential strategies to realize the fabrication of flexible electronics on a large scale with low cost, and have been widely adopted to fabricate flexible electronic whiskers (e-whiskers). However, the sensors fabricated by these methods are typically fragile to surface damage as their conductive pattern is exposed on the surface. Here, conductive ink formed by zero-dimensional conductive nanomaterials, is used to write on leather to fabricate a leather-based e-whisker. Owing to the porosity of leather, the ink can permeate into the leather and form a three-dimensional conductive pathway. The good mechanical properties and special structure of leather enable the sensor to have good performance in tape tests, abrasion tests and washing tests. Furthermore, when scanning the surface of a substrate, the leather-based e-whisker is sensitive enough to detect a height difference of 50 μm, which makes it capable of surface texture detection, spatial distribution mapping, and wind mapping, etc.

A high charge overpotential and poor cycle stability are the limiting factors in lithium–oxygen (Li–O2) batteries, causing poor round-trip efficiency and cell failure. Many types of electrocatalyst...

Pressure sensor can be applied in a wide range of fields, such as voice recognition, human motions detection and artificial electronic skin, the sensing of which is greatly influenced by the flexibility and stretchability of substrate materials. Here, based on the piezoresistive effect, new kinds of flexible pressure sensors have been realized from a pair of flexible and biocompatible collagen films: one is coated by silver nanowires (Ag NWs) and the other by interdigital electrode, respectively. The collagen films are regenerated from leather waste and could bring economic benefits to society. The prepared pressure sensors are applied for voice recognition and human motion detection. Graphical abstract A flexible pressure sensor based on two layers of regenerated collagen films coated silver nanowires (Ag NWs) and interdigital electrodes respectively are obtained. The flexible collagen films are prepared by dissolving leather waste into ionic liquid, [BMIM]Cl. The fabricated pressure sensor displays potential applications in voice recognition and human physical motion detection, such as finger and wrist bending-releasing, which are expected to access the training data of athletes, monitor some physical activities of patients synchronously and act as a voice recognition device.

This article presents a leather-based respiration sensor based on the ionic conductivity change of leather, caused by humidity variation during breathing. Leather was applied as a flexible substrate due to its biocompatibility, hydroscopicity, porosity, and ionic conductivity. Printing method was employed to fabricate the sensor, which could convert human respiration to electrical signals. By combining the leather with silver nanowires (AgNWs), data about human respiration rate, respiration depth, and respiration pattern can be acquired easily through a noninvasive way. Such sensor could work tens of hours consecutively due to the unique properties of leather.

Flexible transparent conductive electrodes (FTCEs) are essential components for numerous optoelectronic devices. In this work, we have fabricated the hierarchical metal grids (HMG) FTCEs by a facile and low-cost, near-field photolithography strategy. Compared to normal metal grids (MG), the HMG structure can provide distinctly increased conductivity of the electrode yet without obvious reduction of the optical transmittance. This HMG sample possesses excellent optoelectronic performance and high mechanical flexibility, making it a promising component for practical applications.

Metal-organic frameworks (MOFs) with an ordered channel and porosity show great promise for a myriad of purposes. Unfortunately, the coordination bond of metal ions and organic ligands easily weakens in unfavorable environments, which poses a key problem in expanding the application of MOFs. Herein, we report a general and efficient strategy to enhance the stability and preserve the porosity of MOFs by coating them with reduced graphene oxide (rGO). The prepared hybrid material consisted of MOFs and rGO, as the core and the protective shell, respectively. It is worth noting that the obtained MOFs@rGO composite material maintained a well-defined crystal structure and showed good catalytic activity as well as enhanced stability. Notably, this novel and general method of coating MOFs with a thin protective rGO shell will broaden the application fields of MOFs and open up a new avenue for the research of MOFs.

Electronic skin (e‐skin), an important part toward the realization of artificial intelligence, has been developing through comprehending, mimicking, and eventually outperforming skin in some aspects. Most of the e‐skin substrates are flexible polymers, such as polydimethylsiloxane (PDMS). Although PDMS was found to be biocompatible, it is not suitable for long‐time wearing due to its air impermeability. This study reports a simple and designable leather based e‐skin by merging the natural sophisticated structure and wearing comfort of leather with the multifunctional properties of nanomaterials. The leather based e‐skin could make leather, “the dead skin,” repurposed for its sensing capabilities. This e‐skin can be applied in flexible pressure sensors, displays, user‐interactive devices, etc. It provides a new class of materials for the development of multifunctional e‐skin to mimic or even outshine the functions of real skin.

Developing a cost-effective nanolithography strategy that enables the production of subwavelength features with various shapes over large areas is a long-standing goal in the nanotechnology community. Herein, an inexpensive nanolithographic technique that combines the wafer-scale production capability of photolithography with the subwavelength feature size controllability of near-field photolithography was developed to fabricate centimeter-scale up to wafer-scale sub-100-nm variously shaped nanopatterns on surfaces. The wafer-scale elastomeric trench-based photomasks with subwavelength apertures created at the apexes were compatible with mask aligners, allowing for the production of wafer-scale subwavelength nanopatterns with adjustable feature sizes, shapes, and periodicities. The smallest feature sizes of 50 and 80 nm were achieved on positive tone and negative tone photoresist surfaces, respectively, which could be ascribed to a near-field optical effect. The fabricated centimeter-scale nanopatterns were functionalized to study cell-matrix adhesion and migration. Compared to currently developed nanolithographic methods that approach similar functionalities, this facile nanolithographic strategy combines the merits of low cost, subwavelength feature size, high throughput, and varied feature shapes, making it an affordable approach to be used in academic research for researchers at most institutions.

Cycling instability of catalysts is a persisting challenge in heterogeneous catalysis. In this work, we reported an effective in situ strategy for preparing ZIF-8 supported carbon-stabilized Pd nanoparticles (C@Pd/ZIF-8). The original ZIF-8 structure was well-preserved after the formation of Pd nanoparticles and amorphous carbon. Here, the Pd nanoparticles were encapsulated in the carbon matrix with a good dispersion. The as-prepared catalysts showed a better activity and cycling stability for the hydrogenation of C[double bond, length as m-dash]C containing substrates. C@Pd/ZIF-8 catalysts are reusable without significant loss of activity after 5 cycles, exhibiting higher cycling stability than those prepared from directly supported Pd nanoparticles on ZIF-8 (Pd/ZIF-8).

A new tetraazatetracene derivative, 2,3-[4,4'-bis(N,N-diphenylamino)benzyl]-5,12-bis[(triisopropylsilyl)ethynyl]-1,4,6,11-tetraazatetracene (TPAs-BTTT), displays rewritable multilevel memory behavior, which is probably induced by multielectron intramolecular charge transfer (CT).

Here, a facile strategy is reported to efficiently hybridize metal nanoparticles (MNPs) with typical metal–organic frameworks (MOFs) of ZIF-8 (zeolitic imidazolate framework-8), which employs bovine serum albumin (BSA, a serum albumin protein derived from cows) as the amphiphilic stabilizer to increase the affinity of MNP toward MOFs. For instance, the as-synthesized PdNPs/ZIF-8 composites with diameter from 100 to 200 nm always maintain well-defined crystalline structure, and the PdNPs with small size of ∼2 nm are well-dispersed in the crystal of MOFs without serious aggregations due to the BSA stabilizer. In Suzuki cross-coupling reactions of aryl halide, the PdNPs/ZIF-8 as catalysts have exhibited high activity and satisfied reusability owing to the use of BSA stabilizer as well as the fixing of MOFs matrixes. In addition, the strategy also can be extended to synthesize other kinds of MNPs/MOFs hybrid composites with tunable particle size, which brings more opportunity for functional MOFs hybrid materials.