Electronic skins (e-skins) mimic multimodal sensing capabilities of various tactile receptors in natural skin. Herein, a stretchable chromotropic ionic skin is rationally designed to simultaneously detect and decouple multiple stimuli, including in-plane strain, temperature, and pressure. The mutually discriminating trimodal ionic skin consists of mechanochromic, thermoresistive and triboelectric layers that individually function as strain, temperature and pressure sensors, respectively. These three distinct capabilities are integrated into the ionic skin which demonstrates highly sensitive responses to selective external stimuli while upholding high insensitivity to unwanted ones. The structural colors derived from mechanochromic photonic crystals of magnetic ferroferric oxide-carbon nanoparticles respond to strains by color-switching in the full visible spectrum, exhibiting appealing potential in interactive stress visualization. The temperature detection with an exceptional sensitivity of 20.44% per °C is enabled by the thermoresistive effect of ionic hydrogel, while oriented polymer chains embedded in the hydrogel decouple temperature from extraneous stimuli. The multilayer structure consisting of an ionic hydrogel film, a wrinkle-patterned polydimethylsiloxane (PDMS) film with gradient modulus design and a carbon nanotubes/PDMS electrode displays an extraordinary triboelectric effect with a strain-and temperature-insensitive pressure sensing capability. The chromotropic ionic skin facilitates simultaneously accurate measurements, high discriminability and quantitative mapping of complex stimuli, offering new insights into emerging E-skins.

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In this research, hydroxyapatite (HAp) was synthesized from chicken eggshell waste by hydrothermal method for the development of bio-composite material suitable for biomedical implant. However, since environmental influences on natural materials are unique for different geographical locations in the world, the use of agro wastes from these locations need to be investigated. This work provides the detail results of the potentials of eggshell as HAp source. High-density polyethylene (HDPE)/HAp composites were developed by random dispersion of Hap (10, 20, 30 and 40 wt.%) in HDPE matrix, and were designated as HAC10, HAC20, HAC30, and HAC40. The HAp-filled HDPE composites were developed by a hot compression moulding process. The samples were subjected to tensile, flexural, impact, fracture toughness and wear tests according to ASTM standards in order to establish their structural performance as an implant material. Furthermore, the samples were also tested for hydrophilicity using tap water and simulated body fluid (SBF). X-ray diffraction analysis showed strong peaks of hydroxyapatite phase which established that the influence of the selected processing conditions on the poultry eggshell as a natural source for the biomedical application was suitable for the synthesis of high-quality hydroxyapatite. The mechanical properties of the developed composites were enhanced to the level of the required properties expected of an implant material compared to the control sample except for impact strength. Water absorption characteristics of the developed composite samples also displayed expected behaviour in SBF solution than in tap water thereby promoting the material as a good implant material. From the results, the sample with 40 wt.% HAp possess the highest values in the mechanical properties examined while sample from 20 wt.% had the best fracture toughness. The results revealed that these waste eggshells could be successfully converted into useful biocompatible HAp particles needed for the enhancement of the mechanical properties of polymer composites to meet the structural challenges of bio-composites.

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