ABSTRACT
Mimicking natural botanical/zoological systems has revolutionarily inspired four-dimensional (4D) hydrogel robotics, interactive actuators/machines, automatic biomedical devices, and self-adaptive photonics. The controllable high-freedom shape reconfiguration holds the key to satisfying the ever-increasing demands. However, miniaturized biocompatible 4D hydrogels remain rigorously stifled due to current approach/material limits. In this research, we spatiotemporally program micro/nano (µ/n) hydrogels through a heterojunction geometric strategy in femtosecond laser direct writing (fsLDW). Polyethylene incorporated N-isopropylacrylamide as programmable interactive materials here. Dynamic chiral torsion, site-specific mutation, anisotropic deformation, selective structural coloration of hydrogel nanowire, and spontaneous self-repairing as reusable µ/n robotics were identified. Hydrogel-materialized monolayer nanowires operate as the most fundamental block at nanometric accuracy to promise high freedom reconfiguration and high force-to-weight ratio/bending curvature under tight topological control. Taking use of this biomimetic fsLDW, we spatiotemporally constructed several in/out-plane self-driven hydrogel grippers, diverse 2D-to-3D transforming from the same monolayer shape, responsive photonic crystal, and self-clenched fists at µ/n scale. Predictably, the geometry-modulable hydrogels would open new access to massively-reproducible robotics, actuators/sensors for microenvironments, or lab-on-chip devices.
ABSTRACT
By taking into account the dynamic thermophysical and optical properties, the ultrafast thermoelastic response of thin copper film irradiated by femtosecond lasers has been researched. The temperature and stress fields of copper film irradiated by femtosecond lasers are analyzed in this work. The simulation results reveal that the degree of thermomechanical response is much underestimated, especially with higher laser fluence and smaller pulse duration. It is necessary to employ dynamic properties in ultrafast thermoelastic simulation for accuracy.
ABSTRACT
A strongly coupled finite element model of the optical breakdown during femtosecond laser pulse interaction, with different morphology of aluminum nanoparticles in water, was developed. This model provided new insight into the optical breakdown dependence on the nanoparticles' morphology and assembly. This model was used to theoretically investigate a 300 fs laser pulse interaction with uncoupled and plasmon coupled aluminum coated silica shell nanoparticles. This study revealed how the nanoparticles' one-dimensional assembly affected the optical breakdown threshold of its surrounding mediums. The optical breakdown threshold had much stronger dependence on the optical near-field enhancement than on the nanostructure's extinction cross-section. The maximum electric field that is outside of the aluminum nanoparticles, with 2 nm silica shell and 2 nm gap, was more than 4 times greater to the one inside of the aluminum nanoparticles. For dimer and trimer configuration, the calculated lattice cross-section temperatures at each breakdown threshold were below their melting point. It is suggested that water could be ionized by aluminum/silica (core/shell) nanostructure during femtosecond laser exposures without nanoparticles consumption. This model could increase understanding of the aluminum nanoparticle-mediated optical breakdown in water.
ABSTRACT
A set of optical models associated with blood cells are introduced in this paper. All of these models are made up of different parts possessing symmetries. The wrapped phase images as well as the unwrapped ones from two orthogonal directions related to some of these models are obtained by simulation technique. Because the phase mutation occurs on the boundary between nucleus and cytoplasm as well as on the boundary between cytoplasm and environment medium, the equation of inflexion curve is introduced to describe the size, morphology, and substructure of the nuclear cell based on the analysis of the phase features of the model. Furthermore, a mononuclear cell model is discussed as an example to verify this method. The simulation result shows that characterization with inflexion curve based on orthogonal phase images could describe the substructure of the cells availably, which may provide a new way to identify the typical biological cells quickly without scanning.
