Smart wearable visual sensors are promising in many areas such as motion monitoring and interactive devices. However, the realization of both biocompatible and self-adhesiveness simultaneously for directly wearing remains challenging....

Herein, we coalesced a poly(acrylamide-co-N-Acryloyl phenylalanine)/polyacrylamide double-network (P(AMco-APA)/PAM DN) hydrogel with a photonic crystal array, fabricating a mechanochromic sensor for application in flexible medical instruments by naked eye monitoring. The intensified mechanical properties of the DN hydrogel were proved by the mechanical property tests, which are attributed to the interactions of chemical bonds and hydrogen bonds between the two polymer networks. In the range of stress from 0 to 328 kPa, the reflected light wavelength of this sensor changed from 659 to 480 nm and the color changed from red to blue in response; in the range of pressure from 0 to 85 kPa, the sensor exhibited a spectrum changing from 658 nm to 467 nm, covering almost the whole visible color range. The prepared sensor was incorporated into medical instruments including the femoral artery hemostat and bandage to indicate pressure and tensile stress in practical applications. Within the appropriate pressure for wound recovery, the sensitivity and correlation between the external stimulus of pressure and wavelength of this integrated sensor were 5.58 nm•kPa −1 and over 0.99, respectively. Ultimately, the sensor proved to be tough, sensitive, and durable, showing a broad prospect of a series of future applications.

Mesoporous silica materials have been widely used as gas adsorbents due to their excellent adsorption ability, large specific surface area, simple preparation process, and convenient functionalization. In this study, a core–shell mesoporous material MCM-41@SiO2 was synthesized and functionalized by CoCl2, and subsequently KSCN, to prepare an ammonia adsorbent. The adsorbent was proved to possess high surface area, good sphericity, uniform size, good dispersibility, and high adsorption capability following DLS, SEM, TEM, and a static adsorption study. Moreover, the successful functionalization and thermal stability were confirmed by FT-IR, XPS, and TGA. The material was then used to fabricate a glass tube sensor for the rapid naked-eye detection of ammonia gas. The sensor showed good performance in terms of sensing speed, selectivity, accuracy, and reusability. Within 5 s, NH3 could be detected by the discoloration, and a wide NH3 concentration from 20 to 1000 ppm could be detected. It also showed a good linear relationship between discoloration length and ammonia concentration. A reversible color change from blue to yellow indicated the presence of NH3, which was attributed to the formation and disassembly of ammonia-containing complex [Co(NH3)6(NCS)2]. With fast adsorption, naked-eye sensing properties, and good selectivity, the sensor holds good promise for indoor NH3 sensing and other more complicated situations.