Anisotropic and Reversible Deformation of Mesopores and Mesostructures in Silica-Based Films under Mechanical Stimuli toward Adaptive Optical Components

Abstract

Deformation of the mesostructures in surfactant/silica hybrid films and mesoporous silica films prepared on bulky elastomeric substrates is investigated by compressing the substrates along an in-plane direction of the films. The mesostructure in the surfactant/silica hybrid film consists of organized micelles and a silica matrix. The micelles are removed in the mesoporous silica films to leave mesopores. A grazing-incidence small-angle X-ray scattering investigation reveals that the mesostructures with C2mm symmetry anisotropically change under a compressive strain of 6% in both films; shrinkage of the lattice parameters is along the direction of compression and extension in the normal direction. Deformation is reversible below a strain as high as 6%. Anisotropic deformation of the mesostructures results in an anisotropic change of the refractive indices normal and parallel to the direction of the compression. Compression of the surfactant/silica hybrid film induces a decrease of the refractive index parallel to the surface and an increase normal to the surface on the order of 10 −3 , while an opposite result is observed for the mesoporous silica film. The present finding gives us fundamental insight into the development of adaptive optical components for sensing, attenuation, switching, modulation, shutters, filters, and others in soft-material-based devices.

Mesoporous ordered films via self-assembly: trends and perspectives

“…On the other hand, the stress-strain deformation induced in the mesoporous films can also be used to design the material properties as a function of the required application; for instance, the thermoelectric properties of mesoporous ZnO thin films have been found to depend on the stress-strain in the material 62 . Another example is the anisotropic and reversible deformation observed in mesoporous films deposited on elastomeric substrates 63 (Figure 7). The effect of the mechanically induced stress on the optical properties of a mesoporous silica film has been measured by transferring the film onto an elastomeric poly(dimethylsiloxane) PDMS substrate.…”

“…On the other hand, the stress-strain deformation induced in the mesoporous lms can also be used to design the material properties as a function of the required application; for instance, the thermoelectric properties of mesoporous ZnO thin lms have been found to depend on the stress-strain in the material. 62 Another example is the anisotropic and reversible deformation observed in mesoporous lms deposited on elastomeric substrates 63 (Fig. 7).…”

Lithographically Formed Fine Wavy Surface Morphology for Universal Alignment Control of Mesochannels in Mesostructured Silica Films

“…Fine structural control of the films of mesostructured materials, prepared through self-assembly of surfactants, has expanded their applicability into various fields such as optics and electronics. − Mesostructured films with a connectivity in the thickness direction have widely been investigated, and several promising applications have been proposed using their specific mass/charge transfer properties. − On the other hand, anisotropic mesostructured films, wherein the internal structure is controlled in the plane of the film over macroscopic scales, allow development of anisotropic properties such as polarized absorption/fluorescence − and birefringence …”

In Situ Small-Angle Neutron Scattering Investigation of Adsorption-Induced Deformation in Silica with Hierarchical Porosity

“…Adsorption-induced deformation describes the effect that porous materials tend to mechanically deform upon the adsorption of a fluid . This might have implications for the mechanical integrity of the materials, in particular, for highly porous materials such as aerogels , or compliant polymers, and possible applications of this effect for actuators have been proposed. − In mesoporous materials, this effect is determined by the interplay of expansive disjoining pressure due to solid–liquid interfacial energy changes (often called “Bangham effect”), and compressive capillary pressure due to curved liquid–gas interfaces. Capillary condensation in mesoporous materials separates the sample strain measured as a function of relative gas pressure p / p 0 (i.e., the “strain isotherm”) typically into two regimes, a film regime and a filled pore regime with a discontinuous behavior at the transition and a hysteresis between adsorption and desorption.…”