Fig. 1. Schematic diagram of a rod-like molecule of a typical thermotropic liquid crystal nematic phase. The average orientation n of the molecules is indicated by the arrow along the molecular long axis.

Fig. 2. Schematic diagram of the pointing deformation pattern in a nematic liquid crystal

Fig. 3. （a） Fabrication process of LC based optical sensor for ammonia detection； （b） Experimental response time versus binding energy correlation of 5CB anchored to various metal salts upon exposure to DMMP； （c） Schematic of the experimental system for optimizing liquid crystal chemosensors based on machine learning.

Fig. 4. （a） Scanning electron microscope image of a polymer micropillar substrate used to fabricate a liquid crystal-based sensor； （b） Schematic diagram of the arrangement of liquid crystal molecules on the gold-plated substrate； （c） Schematic diagram of the change in the molecular structure of the interface in the presence of nitrogen dioxide； （d） Sensing image showing a bright state under the orthogonal polarized microscope； （e） Dark state of the sensing image under the orthogonal polarized microscope in the presence of nitrogen dioxide.

Fig. 5. （a） Schematic of the polymer liquid crystal fiber sensing preparation process； （b） Schematic of the principle of quantitative VOC sensing using liquid crystal functionalized electrospun fibers.

Fig. 6. Polarized optical microscopy images of liquid crystal droplet patterns formed by （a） applying 1 µL of ethanol solution containing 1% （volume fraction） 5CB on piranha-treated glass slides and （b） applying heptane solution containing 10% （volume fraction） 5CB on octyltrichlorosilane （OTS）-treated glass slides. Polarized light microscopy images of liquid crystal droplet patterns on octyltrichlorosilane-treated glass： （c） in a room environment， （d） after 5 s in a heptane vapor environment， （e） immediately exposed to a room environment， and （f） exposed to a heptane vapor for 5 s.

Fig. 7. Schematic diagram of CNT-PDLC gas sensor. （a） Prepared CNT-PDLC sensing device； （b） Orientation of liquid crystals and carbon nanotubes in the absence of NO₂ gas； （c） Liquid crystals and carbon nanotubes reorganized within the droplet in response to NO₂ gas. Corresponding enlarged views are shown in （b1） and （c1）.

Fig. 8. （a） Helical arrangement of cholesteric liquid crystal molecules； （b） Characteristic selective reflectance spectra of cholesteric liquid crystal.

Fig. 9. （a） Chemical structures of reactive monomers and chiral dopants； （b） Cyclic response cycles of bi-responsive liquid crystal films in air and SO₂ gas.

Fig. 10. Structural changes of self-assembled ionic liquid/liquid crystal droplets during exposure to （a） chloroform gas and subsequent recovery； Corresponding signals extracted from POM and video analysis under （b） chloroform gas and （c） ethanol gas stimulation.

Fig. 11. （a） Schematic diagram of the experimental system for optical fiber gas sensing based on cholesteric liquid crystals； （b） Schematic diagram of the interaction mechanism between the alcohol molecule and CLC； （c） Schematic diagram of the polymer network with Ag⁺ and chitosan chains complexed and crosslinked.

Fig. 12. （a） Preparation scheme of cellulose fluorescent liquid crystal membrane； （b） Schematic diagram of the liquid crystal membrane gas detection device and dual-response behavior of the cellulose liquid crystal membrane； （c） Schematic diagram of the principle of colorimetric gas sensing in two-dimensional code prepared by cellulose liquid crystal ink.

Fig. 13. （a） Hydrogen sulfide gas sensor with polymerizable diacetylene side-chain liquid crystals； （b） Schematic of liquid crystal droplets immobilized on a cell for ammonia sensing， where ammonia released from the cell leads to a radial transition to a bipolar structure of E7_PBA encapsulated in a polymer microcapsule.