Tannery solid waste-derived cross-scale deformable piezoresistive sensors for monitoring human body motions

Collagen fiber-reinforced, tough and adaptive conductive organohydrogel e-skin for multimodal sensing applications

Conductive hydrogels (CHs) with high sensitivity and multifunctional property are considered as excellent materials for wearable devices and flexible electronics. Surface synapses and internal multilayered structures are key factors for highly sensitive pressure sensors. Nevertheless, current CHs lack environmental adaptability, multifunctional perception, and instrument portability, which seriously hinders their application as sensors. Here, waste collagen fibers (buffing dust of leather), polyvinyl alcohol (PVA) and gelatin (Gel) were used as the basic framework of the hydrogel, loaded with a conductive material (silver nanoparticles (BD-CQDs@AgNPs)) and an anti-freezing moisturizer (glycerol (Gly)), resulting in a multifunctional conductive organohydrogel (BPGC-Gly). As a temperature and humidity sensor, it demonstrated an excellent temperature response range (-20-60 °C) and was capable of rapid response (2.4 s) and recovery (1.6 s) to human breathing. As a strain/pressure sensor, it allowed real-time monitoring of human movement and had a high low-pressure sensitivity (S = 4.26 kPa-1, 0-12.5 kPa). Interestingly, BPGC-Gly could also be used as a portable bioelectrode or the acquisition, monitoring and analysis of EMG/ECG signals. In this work, BPGC-Gly was assembled with wireless transmission to achieve multimodal heath detection, which opens new avenues for multi-responsive CHs, comprehensive human health monitoring and next-generation wearable electronic skin (e-skin).

Functional magnetic alginate/gelatin sponge-based flexible sensor with multi-mode response and discrimination detection properties for human motion monitoring

The functional flexible sensors that can simultaneously detect multiple external excitations have exhibited great potential in the human-machine interaction and wearable electronics. However, it is still a primary challenge to develop a multi-mode sensor that can achieve sensitivity equilibrium towards different stimuli, and effectively recognize external stimulus while in a facile and cost-effective material and methodology. This study presented a functional flexible sensor based on natural polymer sodium alginate and gelatin sponge electrode which could detect both external mechanical and magnetic stimuli with superiorities of outstanding sensing capability and stability. With the optimal multilayered structure, it possessed high magnetic responsive sensitivity of 0.45 T-1, excellent stability and recoverability. Its electrical property variations also displayed high sensitivity and durability under cyclic stretching, bending and compressing stimuli for 1000 cycles. More importantly, the sensor could not only respond to magnetic field and compression stimuli with contrary electrical responses, but also recognize the respective input signals to decouple different stimuli in real time. Furthermore, it was developed as electronic skins and smart sensor arrays for human physiological signals and mechanical-magnetic detection. Based on excellent multifunctional response characteristics, the sensor showed significant potential in next-generation intelligent multifunctional electronic system and artificial intelligence.

Zero waste discharge in tannery industries - An achievable reality? A recent review

In the recent times, more attention is on industrial waste management due to the unaffordable space for dump yards and landfills and the increased charges for waste dumping. Even though the vegan revolution and plant-based meat products are booming, the traditional slaughterhouses and the wastes produced by them continue to be a concern. Waste valorisation is an established procedure striving to create a closed chain process in industries where there is no refuse. Although a highly polluting industry, slaughterhouse industry wastes have been recycled to economically viable leather since ancient times. However, the tannery industry is causing pollution in par with or even more than the slaughterhouses. Effective management of the liquid and solid wastes from the tannery is of utmost concern because of its toxicity. The hazardous wastes generated enter the food chain, causing long term impacts in the ecosystem. Several leather waste transformation processes are widely used in the industries, and they are yielding good products of economic value. However careful exploration into the processes and products of waste valorisation are often ignored as long as the transformed waste product is of higher value than the waste. The most efficient and environmentally friendly waste management technique should convert the refuse into a value-added utilization without any toxic leftovers. Zero waste concept is an extension of the zero liquid discharge concept, where the solid waste is also treated and reused to such an extent that there is no residue to be sent to the landfill. This review initially presents the existing methods for the de-toxification of tannery wastes and examines the possibility of solid waste management within the tannery industry to attain zero waste discharge.