A Light-Powered Liquid Crystal Elastomer Spring Oscillator with Self-Shading Coatings

Abstract

The self-oscillating systems based on stimuli-responsive materials, without complex controllers and additional batteries, have great application prospects in the fields of intelligent machines, soft robotics, and light-powered motors. Recently, the periodic oscillation of an LCE fiber with a mass block under periodic illumination was reported. This system requires periodic illumination, which limits the application of self-sustained systems. In this paper, we creatively proposed a light-powered liquid crystal elastomer (LCE) spring oscillator with self-shading coatings, which can self-oscillate continuously under steady illumination. On the basis of the well-established dynamic LCE model, the governing equation of the LCE spring oscillator is formulated, and the self-excited oscillation is studied theoretically. The numerical calculations show that the LCE spring oscillator has two motion modes, static mode and oscillation mode, and the self-oscillation arises from the coupling between the light-driven deformation and its movement. Furthermore, the contraction coefficient, damping coefficient, painting stretch, light intensity, spring constant, and gravitational acceleration all affect the self-excited oscillation of the spring oscillator, and each parameter is a critical value for triggering self-excited oscillation. This work will provide effective help in designing new optically responsive structures for engineering applications.

Self-Jumping of a Liquid Crystal Elastomer Balloon under Steady Illumination

“…where V g = 4 3 πr(t) 3 is the instantaneous gas volume, R is the ideal gas constant, and T is the thermodynamic temperature of the ideal gas.…”

“…Mechanical oscillations are periodic energy conversion between potential energy and kinetic energy, and they usually rely on external alternating excitation to maintain the continuous motion of the system with damping dissipation [ 1 ]. In contrast, self-sustained oscillation is a phenomenon where an object sustains periodic motion upon a constant stimulus; thus, no additional complex human controls and portable batteries are required [ 2 , 3 , 4 ], and its frequency is often determined by its own characteristics [ 5 ]. In addition, self-sustained oscillation generally has good robustness [ 6 ].…”

“…Furthermore, a variety of self-sustained motion modes have been constructed, such as bending [ 23 , 24 , 25 , 26 ], buckling [ 27 , 28 , 29 , 30 ], torsion [ 31 , 32 ], stretching and shrinking [ 33 , 34 ], rolling [ 35 , 36 ], swimming [ 9 ], swinging [ 37 , 38 ], vibration [ 39 , 40 , 41 ], jumping [ 42 , 43 , 44 ], rotation [ 45 ], eversion or inversion [ 46 , 47 ], and even synchronized motion of several coupled self-oscillators [ 48 ]. These self-sustained motions often originate from nonlinear feedback mechanisms including self-shadowing [ 3 , 27 , 28 ], coupling of liquid volatilization and membrane deformation [ 49 ], coupling mechanism among air expansion and liquid column movement [ 50 ], and coupling of plate buckling and chemical reaction [ 18 ].…”

Photothermal Thin Films with Highly Efficient NIR Conversion for Miniaturized Liquid-Crystal Elastomer Actuators

“…In recent years, photo-responsive materials, which convert light energy directly into mechanical work, have attracted significant attention because of their promising applications in light-driven mechanical actuation. Liquid-crystal elastomers (LCEs) have been demonstrated to be some of the most excellent materials for light-driven actuation [ 1 , 2 , 3 , 4 , 5 , 6 ]. LCEs exhibit large and reversible deformations due to the liquid-crystal phase transition induced by heating and cooling cycles [ 7 , 8 , 9 , 10 , 11 , 12 ].…”

Dynamical Behaviors of a Translating Liquid Crystal Elastomer Fiber in a Linear Temperature Field

“…The phenomenon of continuous periodic motion of a system under the influence of a steady external environment stimulation is known as self-excited motion [ 1 , 2 , 3 , 4 ]. To compensate for the energy dissipation consumed by the damping, the periodic motion of self-excited oscillation is maintained by collecting the energy directly from the external environment [ 5 , 6 , 7 ]. This property minimizes the complexity of self-excited oscillation systems, making complicated control system design easier to implement and allowing for high load capacity [ 8 , 9 ].…”