Large amplitude light-induced motion in high elastic modulus polymer actuators

Abstract

Well-defined gradients in molecular alignment have been used as tools to generate large amplitude, light-induced deformations in stiff polymer networks. These systems are reversible, monolithic and based on a simple one-step self-assembly process. To fabricate the actuators, diacrylate dopants containing azobenzene moieties were blended with liquid crystalline diacrylate hosts and photopolymerized in a twisted configuration. The resulting twisted networks were heavily crosslinked with room temperature elastic moduli on the order of 1 GPa. Regardless of the temperature with respect to the glass transitions, subsequent exposure to UV radiation induced anisotropic expansion/contraction, and simple variations in geometry were used to generate uniaxial bending or helical coiling deformation modes. Because mechanical energy is directly related to elastic modulus, these systems are expected to provide significantly greater work output than contemporary polymer actuator materials.

Bleaching and stimulated recovery of dyes and of photocantilevers

“…Increasing α leads to some increased penetration, without showing the long linear decay in reduced intensity seen in Fig 2. For α = 10 we have βI = 2 at most, a value evidently insufficient to satisfy limit (iii). We do not have a finite initial region for small x where the decay is exponential with d eff given in and below eqn (9). For these values of α and β one would have d eff = 3d t .…”

“…Since light and heat have analogous effects, one expects and indeed finds that optical absorption leads to analogous mechanical strains, both in photo-elastomers [5,6] and in photo-glasses [7]. Such a mechanism of mechanical change offers the possibility of micro-opto-mechanical systems (MOMS) where elements can be optically-induced to bend as elastomeric photo-swimmers [8] or as glassy cantilevers [7,9,10]. The bend arises because the contraction is differential with depth since the optical beam is absorbed and is hence weaker with depth.…”

“…1. It is important in micro-opto-mechanical systems (MOMS) where elements can be optically-induced to bend as elastomeric photo-swimmers [8] or as glassy cantilevers [9,10].…”

Photoswitchable Nanomaterials Based on Hierarchically Organized Siloxane Oligomers

“…[18] Additionally, polymer films with splay-bend configuration, in which LC-mesogens gradually change orientation throughout the film cross-section, have shown to exhibit inherently anisotropic bending as well as achieve significantly faster and larger bending when compared to uniaxially aligned films. [19][20][21] The ability of azobenzene photoisomerization to generate anisotropic dimension change and motion in LC networks typically results from increased molecular disorder caused by bent cis-azobenzene relative to networks with rod-like transazobenzene. Such photocontrol of order/disorder has been used to induce rapid nematic-to-isotropic phase transitions in LC films for applications in optical image storage [22] and holography.…”

Photo-responsive Smart Polymer Materials

“…In the final panel, (f), the film was moved nearer to the UV source in an attempt to show the maximum deformation. 20 90 º 정도의 트위스트 변형 그리고 coiling 변형이 가능한 LCE 를 소개하였다( Figure 6). 20 …”