The large expansion of the robotic field in the last decades has created a growing interest in the research and development of tactile sensing solutions for robot hand and body integration. Piezoresistive composites are one of the most widely employed materials for this purpose, combining simple and low cost preparation with high flexibility and conformability to surfaces, low power consumption, and the use of simple read-out electronics. This work provides a review on the different type of composite materials, classified according to the conduction mechanism and analyzing the physics behind it. In particular piezoresistors, strain gauges, percolative and quantum tunnelling devices are reviewed here, with a perspective overview on the most used filler types and polymeric matrices. A description of the state-of-the-art of the tactile sensor solutions from the point of view of the architecture, the design and the performance is also reviewed, with a perspective outlook on the main promising applications.

Self-healing hydrogels may mimic the behavior of living tissues, which can autonomously repair minor damages, and therefore have a high potential for application in biomedicine. So far, such hydrogels have been processed only via extrusion-based additive manufacturing technology, limited in freedom of design and resolution. Herein, we present 3D-printed hydrogel with self-healing ability, fabricated using only commercially available materials and a commercial Digital Light Processing printer. These hydrogels are based on a semi-interpenetrated polymeric network, enabling self-repair of the printed objects. The autonomous restoration occurs rapidly, at room temperature, and without any external trigger. After rejoining, the samples can withstand deformation and recovered 72% of their initial strength after 12 hours. The proposed approach enables 3D printing of self-healing hydrogels objects with complex architecture, paving the way for future applications in diverse fields, ranging from soft robotics to energy storage.

Amorphous carbon a-C and amorphous hydrogenated carbon a-C:H films were prepared by rf sputtering of a graphite target in argon and argon-plus-hydrogen atmospheres, respectively. The optical-absorption coefficients of these films were measured by a spectrophotometer in the high-absorption range and by photothermal deflection spectroscopy in the low-absorption range. They were also studied by electron-spin-resonance (ESR) measurements. The optical-absorption spectrum is found to have a rather broad peak, in contrast to the sharp rise in absorption near the band gap observed for normal semiconductors. To explain this broad peak, a model density of states (DOS) for these materials is proposed, in accordance with their well-known microstructure. This consists of a pair of broad Gaussian-like distributions lying above and below the Fermi level and separated by about 4 eV, arising out of the π states of the aromatic sixfold rings that comprise the bulk of the graphitic ${\mathit{sp}}^2$ regions, as well as pairs of discrete levels that are about 0.6 eV apart and are produced by fivefold and sevenfold rings present in these regions. The proposed DOS explains the essential features of the optical-absorption spectra and ESR data. The validity of the concept of the optical gap for these materials is also discussed.

The ever‐increasing amount of batteries used in today's society has led to an increase in the demand of lithium in the last few decades. While mining resources of this element have been steadily exploited and are rapidly depleting, water resources constitute an interesting reservoir just out of reach of current technologies. Several techniques are being explored and novel materials engineered. While evaporation is very time‐consuming and has large footprints, ion sieves and supramolecular systems can be suitably tailored and even integrated into membrane and electrochemical techniques. This review gives a comprehensive overview of the available solutions to recover lithium from water resources both by passive and electrically enhanced techniques. Accordingly, this work aims to provide in a single document a rational comparison of outstanding strategies to remove lithium from aqueous sources. To this end, practical figures of merit of both main groups of techniques are provided. An absence of a common experimental protocol and the resulting variability of data and experimental methods are identified. The need for a shared methodology and a common agreement to report performance metrics are underlined.

Amorphous and microcrystalline silicon carbide, undoped and doped, has attracted a great attention for its optical and electrical properties. The introduction of dopant atoms in the network of amorphous films permits the control of electrical properties but it gives rise to a decreasing of the optical gap. Microcrystalline SiC:H films seem to provide films having a wide range of electrical conductivities without drastic change in the optical gap. This paper presents the results of a detailed study on the effects of boron and phosphorus doping on structural, optical, and electrical properties of a‐SiC:H and μc‐SiC:H films. An optical gap as high as 2.1 eV, together with a conductivity of 10⁻³ Ω⁻¹ cm⁻¹, are shown by doped μc‐SiC:H.