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Optical nano- and microactuation
Published in John P. Dakin, Robert G. W. Brown, Handbook of Optoelectronics, 2017
Another photomechanical effect has been observed in ChG when the material absorbs polarized light (Stuchlik et al. 2001, 2004). Reversible photoinduced anisotropy was the first reported by Krecmer et al. (1997) who showed that when a thin amorphous film of As50Se50 deposited on a clamped atomic force microscope cantilever was exposed to polarized irradiation it would exhibit reversible nanocontraction movement. To demonstrate the effect, the research team performed measurements on a 200 μm cantilever beam with a thickness of 0.6 μm. The surface of the beam was covered with a thin 250 nm As50Se50 film. When exposed to polarized light, the beam bent approximately ±1 μm (Stuchlik et al. 2001). Upon irradiation with polarized light, a very small movement in the ChG was measured parallel to the direction of the electric field of the light and a very small expansion was also observed along the axis orthogonal to the electric field.
Perspectives on Light-Driven Micromachines
Published in George K. Knopf, Kenji Uchino, Light Driven Micromachines, 2018
In addition to invention, serendipity, and inspiration, it is imperative that the creative engineer also have the materials and fabrication tools necessary to move the design concepts forward into reality. The impact of novel photo-responsive materials on light-driven machines and systems cannot be overstated. One group of custom designed photo-responsive polymers that show great deal of promise is the shape changing polymers that incorporate azo compounds (Section 5.3). The reversible shape changing photomechanical effect is directly induced by the adsorption of specific wavelengths of light and not the result of any photothermal process. For example, liquid crystalline elastomers with azobenzene are able to exhibit a wide variety of switching behavior, from altering optical properties to surface energy changes to evoking bulk material phase changes (Mahimwalla et al. 2012). These soft azobenzene polymers also have the potential to help create tiny light responsive actuators that mimic the behavior of human muscles (e.g., contraction and extension). By switching between visible and ultraviolet (UV) light it is possible to create artificial cilia to push fluid along a microchannel or form millipede-like legs that propel a “smart sensor” along a surface. Actuation in both cases is achieved by directing a beam of light with a specific wavelength onto the microscale device and not generating an electric field or thermal gradient that may negatively impact the immediate environment. Although a small variety of “proof-of-principle” prototypes have been described in the literature, these engineered material-based systems still require creative engineering and reliable micro-fabrication methodologies to move the technology beyond the current state of basic science.
User-centred design approach with misidentified end-users: case study for smart composite structures
Published in Journal of Engineering Design, 2022
In this paper, a smart composite structure is given as an example of technological module. In order to define what a smart composite structure is, it is essential to first define what a smart structure is. As proposed by D.J. Leo, ‘smart materials are those that exhibit coupling between multiple physical domains’ (Leo 2007). As presented in Figure 1, to obtain smart materials or, by extension, smart structures, lots of physical couplings can be used such as magnetic field and viscosity to obtain magnetorheological effect or light and deformation to obtain a photomechanical effect. A bi-directional response/behavior can be provided by specific couplings such as converse and direct piezoelectric effects.