Miniature actuators are utilized in various application fields, from robotics to medical devices, where compact dimensions, precise movements, and cost-effectiveness are crucial factors. Particularly for applications like braille displays, there is a critical demand for lightweight, portable, and affordable actuators to integrate into daily life for visually impaired people. However, existing actuation technologies such as electroactive polymers, electrorheological materials, and piezoelectric elements often do not meet the specific requirements of miniature actuators, especially for braille displays. Therefore, this study investigates the behavior of electrorheological fluids incorporated into polymer matrices of cellulose and proteins for miniature actuators to overcome the primary challenge of sedimentation through the structuring of the liquid. The gel formulations are tested in three distinct setups: the V-shaped, horizontal plates, and valve system. These experiments demonstrated immediate structural changes in the gel formulations, achieving reversible movement. Furthermore, the valve setup even enabled the analysis of the strength of the hardened mixtures by the resistance against applied air pressure. The results demonstrate that incorporating electrorheological fluids into polymer matrices is not only feasible but also preserves the characteristic behavior of electrorheological fluids under electrical field exposure. This behavior validates the applicability and suitability of modified electrorheological fluid mixtures in miniature actuators.

Solvent polarity and crosslinking density govern lyogel swelling and molecular dynamics revealed by NMR relaxometry. High-polarity solvent forms macroporous and slow solvent exchange, while low-polarity solvent induces shrinkage and faster exchange.

Chemoresponsive P(NiPAAm-co-AA) beads (approximately 3 mm radius) were synthesized via UV-light-induced copolymerization of N-isopropylacrylamide (NiPAAm) and acrylic acid (AA) in aqueous droplets suspended in silicone oil. SEM analysis revealed a closed surface for beads with a 3-fold excess of AA; macroporous morphologies appeared for NiPAAm:AA ratios of 1:1 and 3:1. Swelling behavior was mapped across linear alcohols, acids, esters, and their mixtures, revealing a cononsolvency related to ethanol presence. Beads with a 1:1 monomer ratio exhibited the largest swelling difference between ethanol and ethyl acetate or with mixtures of ethyl acetate and ethanol. Their reversible swelling–shrinkage was fitted to two exponential functions. The time constant of the first fast part is on the order of minutes. The extent of shrinkage is negatively correlated with the logarithmic ethanol fraction in ethyl acetate. Beads in a casing were used to halt the flow of ethyl acetate after a switch to ethanol.

Iron(III)-reinforced poly(N-isopropylacrylamide-co-acrylic acid) organogel beads inside a casing give an intrinsic chemo-mechanical valve. The valve was incorporated in a setup with a stirred reactor for the heterogeneously acid-catalyzed esterification of acetic acid and ethanol. A noninvasive gravimetric control loop was used to validate the autonomous modulation of the hydrodynamic residence time in response to the composition of the reaction mixture. Operating at a 1:1 molar feed ratio, the valve restricted the initial outflow to less than 7 mL·min–1 and autonomously ramped up to a steady state flow of 135 mL·min–1 as the esterification approached thermodynamic equilibrium. The valve opening rate was about half of the reaction rate. The ionically reinforced organogel had enough resilience inside the casing for multiple uses. Soft actuators were thus successfully applied for reaching a self-regulating reactor loop driven by intrinsic chemical feedback of a smart material.