Dual-Responsive Photonic Crystal Sensors Based on Physical Crossing-Linking SF-PNIPAM Dual-Crosslinked Hydrogel

Abstract

Flexible wearable materials have frequently been used in drug delivery, healthcare monitoring, and wearable sensors for decades. As a novel type of artificially designed functional material, photonic crystals (PCs) are sensitive to the changes in the external environment and stimuli signals. However, the rigidity of the PCs limits their application in the field of biometric and optical sensors. This study selects silk fibroin (SF) and poly-N-isopropylacrylamide (PNIPAM) as principal components to prepare the hydrogel with the physical crosslinking agent lithium silicate (LMSH) and is then integrated with PCs to obtain the SF-PNIPAM dual-crosslinked nanocomposite for temperature and strain sensing. The structural colors of the PCs change from blue to orange-red by the variation in temperature or strain. The visual temperature-sensing and adhesion properties enable the SF-PNIPAM dual-crosslinked nanocomposite to be directly attached to the skin in order to monitor the real-time dynamic of human temperature. Based on its excellent optical properties and biocompatibility, the SF-PNIPAM dual-crosslinked nanocomposite can be applied to the field of visual biosensing, wearable display devices, and wound dressing materials.

Bioderived Composite Hydrogel Sensor: Combining Superstretchability, Moisture Retention, and Temperature Resistance for Strain and Temperature Visualization

“…The NIPAM in the bioderived composite hydrogel sensor is a temperature-sensitive monomer, and the phase transition of the NIPAM occurs at the lower critical solution temperature (LCST), which caused the volume shrinkage of the hydrogel with NIPAM, ,− which can reduce the lattice distance of the photonic crystals and result in a blue shift of the structures (Figure a). Therefore, the sensor can also be used for temperature visualization.…”

“…Based on their unique optical properties and stimulus responsiveness, − the photonic crystals are combined with hydrogels or elastomers for the visualization of physical, − chemical, − and biological stimuli. − Park and Chang designed an all-solid-state electrically tuned photonic crystal sensor with flexibility, and the lattice distance decreased with the increase in voltage and resulted in the blue shift of the structural color, which was attached to the 3D structure for verifying its flexible electrochromic performance. Pan et al prepared a biomimetic Janus structured color film with stable electrical sensing and visual optical sensing performance, which met the needs of flexible stretchable electronic products.…”

Stimuli‐responsive active materials for dynamic control of light field

“…The resulting TCSs exhibited programmable thermochromic responses with excellent cyclic stability. Zheng et al [73] . prepared a nanocomposite for temperature sensing by combining a hydrogel composed of silk fibroin and poly‐ N ‐isopropyl acrylamide with a colloidal photonic crystal template.…”

Naked-Eye Visual Thermometer Based on Glycerol─Nonclose-Packed Photonic Crystals for Real-Time Temperature Sensing and Monitoring

“…Thermochromic hydrogels based on the PCs can sense temperature changes through their structural colors, which was the result of lattice distance tuning with temperature, and the tuning ranges of reflection peak was mostly within 100 nm (Table S1). − To enhance the effect of visualization, thermochromic hydrogels based on inverse opal PCs were proposed. The decrease of lattice distance and the effective refractive index were combined to get a greater blueshift of the PBG (Table S2), − which achieved temperature visual sensing in all the wavelength range.…”