Mechano-Optical Response Behavior of Polymer-Dispersed Cholesteric Liquid Crystals for Reversible and Highly Sensitive Force Recorders

Abstract

Force recording (mode, intensity, and orientation) is of great importance in medical rehabilitation, military reconnaissance, space exploration, etc. However, sensors with both reversibility and memorability are still challenging. Here, a reversible sensor based on polymer-dispersed cholesteric liquid crystals (CLC) is developed as a force recorder. Based on the microarea mechano-optical response and finite element analysis, it is confirmed that the mechanochromic response is mediated by the shear deformation of the polymer network and neighboring CLC. There is an obvious quantitative relationship between force intensity, mode, orientation, and the microarea optical response. Moreover, the sensing layer with a lower modulus or thickness is advantageous for a more sensitive device with lower starting pressure. Additionally, the excellent sensitivity and accuracy also highlight the potential applications in force analysis, path tracking, or pattern detection.

Progress in Fabrication and Applications of Cholesteric Liquid Crystal Microcapsules

“…This may pave the way for applications of novel mechanosensitive materials, such as strain sensors. Ge et al [122] developed a reversible mechanochromic recorder with a "sandwich" structure in which a conductivetreated polyethylene terephthalate (PET) film serves as the upper transparent sensing layer and the dark supporting layer, while polymer-dispersed CLCs serve as the color storage layer. Upon sufficient pressure, the CLC in the polymer network in color storage layer flows away, causing the CLC molecules to align to the planar state, which reflects the incident light and produces bright structural colors.…”

Preparation and Orthogonal Analysis for Dual-Responsive Electrochromic Polymer Dispersed Liquid Crystal Devices

“…At present, PDLCs demonstrate tremendous potential for a variety of applications including physical and chemical sensors [20][21][22], displays [23,24], time temperature indicators [25], smart windows [26], etc. The electro-optical performance of PDLCs has been improved in various strategies, such as doping guests (e.g., dyes [27] and nanoparticles [14,28]), utilizing LC elastomers [29], and innovating novel modes [30][31][32].…”

Design and multilevel structuring of shape memory polymers for pleochroism control

“…6 An even more interesting mechanical-optical behavior was found in films containing cholesteric liquid crystals dispersed in a polymer. 7 Multicolor films with useful optical properties that respond to various external actions can be commercially produced for optical sensor applications. 8 The optical properties of these sensors are very sensitive to changes in temperature, light polarization, electric field, mechanical stress, or sorption of vapors and liquids.…”

“…Polymeric materials with shape memory effects are used in medicine, [1][2][3][4][5][6] orthopedics, [7][8][9][10][11][12][13] and pharmacology [14][15][16][17][18] for manufacturing endoprostheses [19][20][21] and implants. 22 Fibers and films with shape memory are used as biodegradable sutures and patches pulling together living tissues of the body.…”

“…It has been proven that the penetration of liquid into polymer films made from block copolymers causes the appearance of a reversible structural color 6 . An even more interesting mechanical‐optical behavior was found in films containing cholesteric liquid crystals dispersed in a polymer 7 . Multicolor films with useful optical properties that respond to various external actions can be commercially produced for optical sensor applications 8 .…”