Next-generation of smart dressings: Integrating multiplexed sensors and theranostic functions

Non-healing wounds represent a significant burden for healthcare systems and society, giving rise to severe economic and human issues. Currently, the use of dressings and visual assessment represent the primary and standard care for wounds. Conventional dressings, like cotton gauze, provide only passive physical protection. Besides, they end up paradoxically hampering the wound-healing process by producing tissue damage and pain when removed during routine check-ups. In response to these limitations, researchers, engineers, and technologists are developing innovative dressings that incorporate advanced diagnostic and therapeutic functionalities, coined as "smart dressings". Now, the maturation of smart dressing is bringing them closer to real-life applications, leading to an exciting new generation of these devices. The next generation of smart dressings is capable of monitoring in real-time multiple biomarkers while including pro-healing capabilities in a single platform. Such multiplexed and theranostic smart dressings are expected to offer a timely biomarker-directed diagnosis of non-healing wounds while enabling rapid, automated, and personalized treatments of infection and chronicity. Herein, we provide an insightful overview of these advantageous devices, delving into the diverse spectrum of possible engineering strategies. This encompasses the use of electrochemical and optical platforms with diverse multiplexing architectures, such as multi-zone sensing arrays and multi-layered devices. Open or closed-loop theranostic mechanisms using various stimuli-responsive materials that could be internally or externally controlled are also included. Finally, a critical discussion on the main challenges and future directions of smart dressings is also offered.

A hybrid multifunctional physicochemical sensor suite for continuous monitoring of crop health

This work reports a first-of-its-kind hybrid wearable physicochemical sensor suite that we call PlantFit for simultaneous measurement of two key phytohormones, salicylic acid, and ethylene, along with vapor pressure deficit and radial growth of stem in live plants. The sensors are developed using a low-cost and roll-to-roll screen printing technology. A single integrated flexible patch that contains temperature, humidity, salicylic acid, and ethylene sensors, is installed on the leaves of live plants. The strain sensor with in-built pressure correction capability is wrapped around the plant stem to provide pressure-compensated stem diameter measurements. The sensors provide real-time information on plant health under different amounts of water stress conditions. The sensor suite is installed on bell pepper plants for 40 days and measurements of salicylic acid, ethylene, temperature, humidity, and stem diameter are recorded daily. In addition, sensors are installed on different parts of the same plant to investigate the spatiotemporal dynamics of water transport and phytohormone responses. Subsequent correlation and principal component analyses demonstrate the strong association between hormone levels, vapor pressure deficit, and water transport in the plant. Our findings suggest that the mass deployment of PlantFit in agricultural settings will aid growers in detecting water stress/deficiency early and in implementing early intervention measures to reduce stress-induced yield decline.

Metasurfaces for Sensing Applications: Gas, Bio and Chemical

Performance of photonic devices critically depends upon their efficiency on controlling the flow of light therein. In the recent past, the implementation of plasmonics, two-dimensional (2D) materials and metamaterials for enhanced light-matter interaction (through concepts such as sub-wavelength light confinement and dynamic wavefront shape manipulation) led to diverse applications belonging to spectroscopy, imaging and optical sensing etc. While 2D materials such as graphene, MoS₂ etc., are still being explored in optical sensing in last few years, the application of plasmonics and metamaterials is limited owing to the involvement of noble metals having a constant electron density. The capability of competently controlling the electron density of noble metals is very limited. Further, due to absorption characteristics of metals, the plasmonic and metamaterial devices suffer from large optical loss. Hence, the photonic devices (sensors, in particular) require that an efficient dynamic control of light at nanoscale through field (electric or optical) variation using substitute low-loss materials. One such option may be plasmonic metasurfaces. Metasurfaces are arrays of optical antenna-like anisotropic structures (sub-wavelength size), which are designated to control the amplitude and phase of reflected, scattered and transmitted components of incident light radiation. The present review put forth recent development on metamaterial and metastructure-based various sensors.