Scientists have developed an ingenious way of responding to light by converting light into energy. This can be useful in harnessing the energy used in soft-spoken robots and micro-electromechanical system (MEMS) devices. Many ingenious things have been done successfully to replicate the most common responsive behaviors in nature such as Venus flytrap, pine cone, Mimosa pudica leaf (a plant that says ‘do not touch me’), or sunflower that is constantly trying to counteract the Sun. The Venus flytrap closes its ciliated leaves when the deer is nearby.
Liquid crystal polymer (LCNs) networks are one such smart thing. In thermal application, an equally aligned LCN film undergoes a 2 or 3-dimensional reversible change caused by the LC liquid phase transition. By changing the intermediate shape of the LC molecule-shaped molecules, various aging processes such as bending, folding, and even the formation of curved ribbons have been achieved in the past.
However, earlier devices needed additional layers of film-turning film to achieve bi-directional actuation — converting external forces into motion. As a solution to this problem, in a joint study, researchers at the Nano and Soft Matter Sciences (CeNS) institute, Bengaluru, an independent institute of the Department of Science and Technology (DST), and the Department of Mechanical Engineering, IIT. Madras, made LCN’s Splay-deformed (spread out) LCN films, by combining a mixture of mono-functional and bi-functional liquid crystal masogens (chemical compounds). Two types of liquid crystalline meses combine a single-cell unit to absorb light, respectively, and combine a near-red dye (NIR) – that is active in the system. The film N-LAser-based NIR causes a significant increase in local temperature, and subsequent change-order changes lead to changes in macroscopic form or, in other words, thermo-mechanical function. The study was published in the journal Soft Matter.
Drs. DivyaJayoti (currently in IIT Madras) and Prof. S. Krishna Prasad pointed out that a larger, faster, and more direct action can be achieved by carefully adjusting the geometric parameters and elements of the film. Drs. Ratna Kumar Annabattula and Mr. Akhil R. Peeketi at IIT Madras did modeling and imitating thermal performance. Further expansion of the work has shown that the films also perform much better under solar renewal, suggesting that they can be used to harness solar power to use inexpensive robots and MEMS devices.
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