In modern society, technology associated with smart sensors made from flexible materials is rapidly evolving. As a core component in the field of wearable smart devices (or ‘smart wearables’), flexible sensors have the advantages of excellent flexibility, ductility, free folding properties, and more. When choosing materials for the development of sensors, reduced weight, elasticity, and wearer’s convenience are considered as advantages, and are suitable for electronic skin, monitoring of health-related issues, biomedicine, human–computer interactions, and other fields of biotechnology. The idea behind wearable sensory devices is to enable their easy integration into everyday life. This review discusses the concepts of sensory mechanism, detected object, and contact form of flexible sensors, and expounds the preparation materials and their applicability. This is with the purpose of providing a reference for the further development of flexible sensors suitable for wearable devices.

Heap bioleaching is a microbial technology that catalyzes the decomposition of ore without grinding. The crushed ore is stacked on the liner, and the microbial solution flows through the heap from top to bottom. Under the oxidation action of Fe³⁺, valuable metals in sulfide enter the liquid phase as ions, which are then recovered from the subsequent process. The main function of microorganisms are the regeneration of Fe³⁺. This technology has the advantages of low cost, environment friendliness, simple requirements, and suitability for the treatment of low-grade ore. It has been applied to industrial production. However, the technology is still evolving because there are still many problems that are not well explained, such as synergistic effect between microorganisms, the role of extracellular polymeric substances, passivation phenomenon, galvanic interaction between minerals, mode of ore treatment and heap running, the impact of the natural environment, reasonable disposal of tailings, etc. This paper adequately discusses these aspects based on plentiful excellent researches, including the latest ideas, which can provide a comprehensive and in-depth knowledge of heap bioleaching for the readers. Besides, commercial process data, effective improvement measures, environmental protection ways, laboratory research, and optimization methods were reviewed. Based on the comparative analysis of these knowledges, the recommended technical parameters and the remaining challenges are displayed, which can guide a new commercial or pilot-scale heap. Researchers can make new explorations from the potential research directions and methods proposed in this paper, so that heap bioleaching technology can better serve social development.

Secondary copper smelting is an effective means of treating waste resources. During the smelting process, the viscous behavior of the smelting slags is essential for smooth operation. Therefore, the effects of Fe/SiO₂ ratio and Fe₂O₃ contents on the viscous behavior of the FeO−Fe₂O₃−SiO₂−8 wt%CaO−3 wt%MgO−3 wt%Al₂O₃ slag system were investigated. The slag viscosity and activation energy for viscous flow decrease with increasing Fe/SiO₂ from 0.8 to 1.2, and increase as the Fe₂O₃ content increases from 4 wt% to 16 wt% at Fe/SiO₂ ratio of 1.2. However, under the conditions of Fe/SiO₂ of 0.8 and 1.0, the viscosity and activation energy for viscous flow show a minimum value at Fe₂O₃ content of 12 wt%. Fe₂O₃ exhibits amphoteric properties. In addition, the increase in Fe₂O₃ content raises the breaking temperature of the slag, while the Fe/SiO₂ ratio has the opposite effect. Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy show that increases in Fe/SiO₂ ratio lead to simplification of the silicate network structure, while increases in Fe₂O₃ content improves the formability of the network. This study provides theoretical support for the related research and application of secondary copper smelting.

With the rapid development of wearable technology, multifunctional sensors have demonstrated immense application potential. However, the limitations of traditional rigid materials restrict the flexibility and widespread adoption of such sensors. Hydrogels, as flexible materials, provide an effective solution to this challenge due to their excellent stretchability, biocompatibility, and adaptability. This study developed a multifunctional flexible sensor based on a composite hydrogel of polyvinyl alcohol (PVA) and sodium alginate (SA), using poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate (PEDOT:PSS) as the conductive material to achieve multifunctional detection of strain, temperature, and physiological signals. The sensor features a simple fabrication process, low cost, and low impedance. Experimental results show that the prepared hydrogel exhibits outstanding mechanical properties and conductivity, with a strength of 118.8 kPa, an elongation of 334%, and a conductivity of 256 mS/m. In strain sensing, the sensor demonstrates a rapid response to minor strains (4%), high sensitivity (gauge factors of 0.39 for 0–120% and 0.73 for 120–200% strain ranges), short response time (2.2 s), low hysteresis, and excellent cyclic stability (over 500 cycles). For temperature sensing, the sensor achieves high sensitivities of −27.43 Ω/K (resistance mode) and 0.729 mV/K (voltage mode), along with stable performance across varying temperature ranges. Furthermore, the sensor has been successfully applied to monitor human motion (e.g., finger bending, wrist movement) and physiological signals such as electrocardiogram (ECG), electromyogram (EMG), and electroencephalogram (EEG), highlighting its significant potential in wearable health monitoring. By employing a simple and efficient fabrication method, this study presents a high-performance multifunctional flexible sensor, offering novel insights and technical support for the advancement of wearable devices.