Optical humidity sensing and ultrasound effect for mesoporous silicon one-dimensional photonic crystals

Programmable Color in a Free-Standing Photonic Microgel Film with Ultra-Fast Response

In this work, a free-standing microgel film with programmable and angle-independent structural color is prepared via a simple but effective method. Dried poly(styrene-N-isopropylacrylamide-acrylic acid) (pStNIPAAmAA) microgels were stabilized by inter-microgel crosslinking, and thus, only microgels were used to build the optical hydrogel. The free-standing microgel film displayed tunable structural color by the swelling/deswelling of the microgels under external stimuli, such as temperature, pH, ionic strength, and organic solvent. Moreover, the structural color of the film is angle-independent for the disordered microgel arrays. It is worth noting that programmable color stripes which have the panther chameleon's ability to change skin color are successfully fabricated by patterning microgels with different thermoresponsivities. More importantly, the microgel film has an ultrafast response to temperature (1.41 s from 20 to 40 °C) and pH (2.24 s from pH 8.3 to pH 2.0), much faster than that of most optical materials reported in previous studies.

Photonic crystals for chemical sensing and biosensing

This Review covers photonic crystals (PhCs) and their use for sensing mainly chemical and biochemical parameters, with a particular focus on the materials applied. Specific sections are devoted to a) a lead-in into natural and synthetic photonic nanoarchitectures, b) the various kinds of structures of PhCs, c) reflection and diffraction in PhCs, d) aspects of sensing based on mechanical, thermal, optical, electrical, magnetic, and purely chemical stimuli, e) aspects of biosensing based on biomolecules incorporated into PhCs, and f) current trends and limitations of such sensors.