South China University of Technology

Since the first design of tactile sensors was proposed by Harmon in 1982, tactile sensors have evolved through four key phases: industrial applications (1980s, basic pressure detection), miniaturization via MEMS (1990s), flexible electronics (2010s, stretchable materials), and intelligent systems (2020s-present, AI-driven multimodal sensing). With the innovation of material, processing techniques, and multimodal fusion of stimuli, the application of tactile sensors has been continuously expanding to a diversity of areas, including but not limited to medical care, aerospace, sports and intelligent robots. Currently, researchers are dedicated to develop tactile sensors with emerging mechanisms and structures, pursuing high-sensitivity, high-resolution, and multimodal characteristics and further constructing tactile systems which imitate and approach the performance of human organs. However, challenges in the combination between the theoretical research and the practical applications are still significant. There is a lack of comprehensive understanding in the state of the art of such knowledge transferring from academic work to technical products. Scaled-up production of laboratory materials faces fatal challenges like high costs, small scale, and inconsistent quality. Ambient factors, such as temperature, humidity, and electromagnetic interference, also impair signal reliability. Moreover, tactile sensors must operate across a wide pressure range (0.1 kPa to several or even dozens of MPa) to meet diverse application needs. Meanwhile, the existing algorithms, data models and sensing systems commonly reveal insufficient precision as well as undesired robustness in data processing, and there is a realistic gap between the designed and the demanded system response speed. In this review, oriented by the design requirements of intelligent tactile sensing systems, we summarize the common sensing mechanisms, inspired structures, key performance, and optimizing strategies, followed by a brief overview of the recent advances in the perspectives of system integration and algorithm implementation, and the possible roadmap of future development of tactile sensors, providing a forward-looking as well as critical discussions in the future industrial applications of flexible tactile sensors.

Surface immobilization of antimicrobial peptides (AMPs) on implants offers promising efficacy against drug-resistant bacterial infections. The cationically amphipathic structure of AMPs, while crucial for their potent antimicrobial activity, poses substantial challenges for achieving scalable coatings on implants and contributes to their cytotoxicity toward normal tissues/cells. Herein, we developed hydrophobicity-to-cationic amphipathicity transformable AMPs (HAT-AMPs) for scalable coating on medical implant, effectively preventing bacterial infections while exhibiting low cytotoxicity to normal tissues. The HAT-AMPs, composed of ionizable and hydrophobic residues, are hydrophobic and electrically neutral at physiological pH condition, making them highly suitable for physical immobilization on titanium surfaces while exhibiting minimal toxicity to normal tissues. In acidic environments during infections, the protonation of ionizable units induces HAT-AMPs to adopt a cationically amphipathic structure, remarkably enhancing their antimicrobial activity by targeting bacterial phospholipid phosphatidylglycerol. When immobilized on titanium implant surface, the coating exhibited a favorable safety profile, and demonstrated strong antibacterial efficacy and promising wound-healing potential in a subcutaneous infection mouse model. This strategy offers an efficient approach for fabricating infection-responsive implant coatings.

As a typical multi-enzymic nanozyme, Prussian blue nanozymes (PBNZs) mimic the catalytic functions of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) enzymes in a pH-dependent manner. Due to their capacity to modulate reactive oxygen species (ROS), PBNZs are considered a promising tool for immune modulation, particularly in the directional regulation of macrophage polarization. However, the biological dynamics of pH-dependent multienzyme activity in cells remain poorly understood. Here, we demonstrate that the intracellular localization of PBNZs is a critical factor in their regulation of ROS and macrophage polarization. Smaller-sized PBNZs (3 nm) efficiently bypass acidic lysosomal environments (pH 4.6) and accumulate in the cytosol (pH 7.4) where they exhibit reduced POD-mimic activity and enhanced CAT- and SOD-mimic functions. Conversely, larger-sized PBNZs (60 nm and 170 nm) predominantly remained in acidic lysosomes (pH 4.6), exhibiting stronger POD-mimic activity but minimal CAT-mimic function. Additionally, we identify hypoxia-inducible factor 1-alpha (HIF-1a) as a potential mediator that senses alterations in intracellular oxygen(O₂) levels induced by PBNZs, thus modulating the transcription of genes involved in macrophage polarization. Moreover, oral administration with 3 nm PBNZs effectively mitigated dextran sodium sulfate (DSS)-induced acute colitis in mice, owing to their great capacity to modulate macrophage function. Our study provides insights into the complex behavior of multi-enzymatic PBNZs within the intracellular milieu, reveals their protective effect in treating colitis, and offers a foundational rationale for the tailored design of multi-enzymic nanozymes with specific macrophage modulatory properties for prophylactic applications.