Photomechanics, i.e., the conversion of light into thermal and mechanical work is of significant importance for energy conversion/reconfigurable technologies. Advantages of such photo-thermal mechanisms for transducers include remote energy transfer, remote controllability, control of actuation using number of photons (intensity) and photon energies (wavelength), fast actuation (milliseconds), low signal to noise ratio, high stored elastic strain energy densities with hyperelastic elastomers and scalability at different length scales using batch fabrication and high-volume semiconductor manufacturing. However, only a few materials exist that can convert light into mechanical work. Azobenzene liquid crystal elastomers were one of the first materials to exhibit the photomechanical effect. However, their application required two different light sources for reversible thermal switching (420 nm and 365 nm) between an extended trans and a shorter cis configuration. In this talk, we will cover how light is used with new materials to create the mechanical effect. New nanomaterials, when mixed with polymeric materials, show the unusual photomechanical effect that can be practically harnessed for real-world application. Straining new 2D nanomaterials such as graphene, MoS2 and others creates a new effect called the coupled straintronic photo-thermic effect enables large light absorption and also increase in mechanical effect. The talk will go through an overview of this new and upcoming area of research based on light-matter interaction in 1D and 2D nanomaterial composites.
The ability to convert photons of different wavelength directly into mechanical motion is of significant interest in many energy conversion and reconfigurable technologies. Using few layer 2H-MoS2 nanosheets, layer by layer process of nanocomposite fabrication, and strain engineering, we demonstrate a reversible and chromatic mechanical response in MoS2-nanocomposites between 405 nm to 808 nm with large stress release. The chromatic mechanical response originates from the d orbitals and is related to the strength of the direct exciton resonance A and B of the few layer 2HMoS2 affecting optical absorption and subsequent mechanical response of the nanocomposite. The unique photomechanical response in 2H-MoS2 based nanocomposites is a result of the rich d electron physics not available to nanocomposites based on sp2 bonded graphene and carbon nanotubes, as well as nanocomposite based on metallic nanoparticles. The reversible strain dependent optical absorption suggest applications in broad range of energy conversion technologies.
In this work, a combined experimental and numerical approach, called Extended Load Confluence Algorithm (ELCA), is presented to effectively improve the accuracy of the dynamic modeling of a structural system through an iterative approach. ELCA reconstructs the full-field dynamic response based on a numerical model of the system, its modal expansion and a few experimental measurements. From an initial guess of the applied loads, the algorithm updates it at each iteration to improve the accuracy in the representation of the dynamic response. Numerical validation cases are presented to show the effectiveness of proposed approach. The convenience of the proposed approach can be considerably beneficial when applied to structures with complex loading conditions in aerospace and mechanical applications.