Electrically Driven Artificial Muscles Using Novel Polysiloxane Elastomers Modified with Nitroaniline Push–Pull Moieties

Abstract

The synthesis of novel dielectric elastomers that show a muscle-like actuation when exposed to a low electric field represents a major challenge in materials science. Silicone elastomers modified with polar side groups are among the most attractive dielectrics for such a purpose because of their high polarizability over a wide temperature and frequency range. Nitroaniline (NA) has a strong dipole moment, and therefore, its incorporation into silicone networks should allow the formation of elastomers with increased dielectric permittivity. However, incorporation of a large amount of NA into silicone needed to increase the dielectric permittivity is still challenging. In this work, we present the synthesis of polysiloxane elastomers modified with a large fraction of the nitroaniline (NA) polar group, following two different synthetic strategies. Both approaches allowed the formation of homogenous elastomers at the molecular level. These yellowish materials have a dielectric permittivity three times higher as compared to the reported NA-modified silicones. Additionally, they have excellent mechanical properties with low viscoelastic losses and a strain at break reaching 300%. Furthermore, the mechanical properties of these elastomers can be easily tuned by the content of cross-linkers used. The developed elastomers are highly stable in electromechanical tests and show an actuation strain of 8% at unprecedentedly low electric fields of 7.5 V/μm. The combination of properties such as high dielectric permittivity, large strain at break, low viscoelastic losses, fast and reversible actuation, and actuation at low electric fields is crucial for the new generation of dielectric elastomer materials that will find their way in applications ranging from artificial muscles, soft robots, sensors, and haptic displays to electronic skin.

Soft, tough, and fast polyacrylate dielectric elastomer for non-magnetic motor

“…c The stress–strain curves of commercial VHB TM 4910 and BA-S, BA-M, BA-L, BAC2 at a stretch rate of 200 mm min −1 . d Comparison of ultimate strength to modulus among VHB TM 4910, BA-S, BA-M, BA-L, BAC2, dielectric gel 37 , multiblock copolymers 33 , azo-grafted silicone 28 , nitroaniline modified silicone 18 , polyurethane 19 , alkyl thiols grafted silicone 16 and commercial Elastosil@Film 16 . e , Toughness plotted against Young’s modulus for VHB TM 4910, BA-S, BA-M, BA-L, BAC2, dielectric gel 37 , silicones with ionic liquids 17 , acrylic copolymer 25 , nitroaniline modified silicone 18 , nitrile modified silicone 39 , alkyl thiols grafted silicone 16 , 3D printable silicone 40 , and commercial Elastosil@Film 16 ( Supplementary Discussion ).…”

“…Different from the actuators with ferroelectric polymers 11,13 , dielectric elastomer actuator (DEAs), an electrically stimulus-responsive actuator, show great potential for the large strain and superior flexibility 8,12,14,15 . A large variety of commercial elastomers, including silicone rubbers 9,[16][17][18] , polyurethanes 19 , and acrylic elastomers (e.g., VHB TM 4910 from 3 M) 8,20 , have been widely used to assemble DEAs. Among them, acrylic-based elastomers outperform others for composing non-magnetic motors because of their high dielectric constant (~4.4@1 kHz), large area strain (>380%), and high energy density (3.4 MJ m −3 ) 8 .…”

Low‐Voltage Soft Actuators for Interactive Human–Machine Interfaces

“…[195,197,199] In addition, as greater dissimilarity between positive and negative centers of the polymer chains arises, further contributions from atomic polarization improve the dielectric constant. [220] Various polar groups such as cyanoester, [238] azobenzene, [239] sulfonyl, [240] polyethylene glycol, [209] thioether, [241] nitroaniline, [242] and nitrile [203,243,244] have been introduced to the polymer backbone to enhance the dielectric constant. Following this strategy, Perju et al synthesized a silicone elastomer with large amounts of nitroaniline functionalities that raised dielectric constants to 18.7 at 1 kHz.…”

High-permittivity silicone dielectric elastomers compatible with ionic liquid-grafted chloropropyl-silicone oil

“…Dielectric elastomers (DEs) are promising soft electroactive materials [1], which can significantly alter their size or shape in response to an external electrical field [2]. Due to their low weight, low cost, fast response, and high efficiency [3], DEs are widely used in transducers such as artificial muscles [4], energy harvesters [5], and haptic devices [6]. DEs consist of an elastomer film sandwiched between two compliant electrodes, thereby creating a capacitor capable of energy transduction.…”