All-optical driven soft crawler with complexmotion capabilities

The emergence of millimeter-scale soft actuators has signifi-cantly expanded the potential applications in areas such as search and rescue,drug delivery,and human assistance,due to their high flexibility.Despite these advancements,achieving precise control over the intricate movements of soft crawlers poses a significant challenge.In this study,we have developed an all-optical approach that enables manipulation of propul-sive forces by simultaneously modifying the magnitude and direction of friction forces,thereby enabling complex motions of soft actuators.Importantly,the approach is not constrained by specific actuator shapes,and theoretically,any elongated photothermal actuator can be employed.The actuator was designed with an isosceles trapezoid shape,featuring a top width of 2mm,a bottom width of 4 mm,and a length of 8 mm.Through our,manipulation approach,we showcase a proof-of-concept for complex soft robotic motions,including crawling(achieving speeds of up to 2.25 body lengths per minute),turning,avoiding obstacles,handling and trans-ferring objects approximately twice its own weight,and navi-gating narrow spaces along programmed paths.Our results showcasethis all-optical manipulationapproach as a promising,yet unexplored tool for the precision and wireless control for the development of advanced soft actuators.

Three-dimensional chiral microstructures fabricated by structured optical vortices in isotropic material

Optical vortices,a type of structured beam with helical phase wavefronts and‘doughnut’-shaped intensity distributions,have been used to fabricate chiral structures in metals and spiral patterns in anisotropic polarization-dependent azobenzene polymers.However,in isotropic polymers,the fabricated microstructures are typically confined to non-chiral cylindrical geometry due to the two-dimensional‘doughnut’-shaped intensity profile of the optical vortices.Here we develop a powerful strategy to realize chiral microstructures in isotropic material by coaxial interference of a vortex beam and a plane wave,which produces threedimensional(3D)spiral optical fields.These coaxial interference beams are generated by designing contrivable holograms consisting of an azimuthal phase and an equiphase loaded on a liquid-crystal spatial light modulator.In isotropic polymers,3D chiral microstructures are achieved under illumination using coaxial interference femtosecond laser beams with their chirality controlled by the topological charge.Our further investigation reveals that the spiral lobes and chirality are caused by interfering patterns and helical phase wavefronts,respectively.This technique is simple,stable and easy to perform,and it offers broad applications in optical tweezers,optical communications and fast metamaterial fabrication.

Efficient full-path optical calculation of scalar and vector diffraction using the Bluestein method

Efficient calculation of the light diffraction in free space is of great significance for tracing electromagnetic field propagation and predicting the performance of optical systems such as microscopy,photolithography,and manipulation.However,existing calculation methods suffer from low computational efficiency and poor flexibility.Here,we present a fast and flexible calculation method for computing scalar and vector diffraction in the corresponding optical regimes using the Bluestein method.The computation time can be substantially reduced to the sub-second level,which is 105 faster than that achieved by the direct integration approach(~hours level)and 102 faster than that achieved by the fast Fourier transform method(~minutes level).The high efficiency facilitates the ultrafast evaluation of light propagation in diverse optical systems.Furthermore,the region of interest and the sampling numbers can be arbitrarily chosen,endowing the proposed method with superior flexibility.Based on these results,full-path calculation of a complex optical system is readily demonstrated and verified by experimental results,laying a foundation for real-time light field analysis for realistic optical implementation such as imaging,laser processing,and optical manipulation.

Rapid fabrication of microrings with complex cross section using annular vortex beams

A ring-shaped focus, such as a focused vortex beam, has played an important role in microfabrication and optical tweezers.The shape and diameter of the ring-shaped focus can be easily adjusted by the topological charge of the vortex. However,the flow energy is also related to the topological charge, making the individual control of diameter and flow energy of the vortex beam impossible. Meanwhile, the shape of the focus of the vortex beam remains in the hollow ring. Expanding the shape of focus of structural light broadens the applications of the vortex beam in the field of microfabrication. Here, we proposed a ring-shaped focus with controllable gaps by multiplexing the vortex beam and annular beam. The multiplexed beam has several advantages, such as the diameter and flow energy of the focal point can be individually controlled and are not affected by the zero-order beam, and the gap size and position are controllable.

Reply to Comments on “Efficient full-path optical calculation of scalar and vector diffraction using the Bluestein method”

Dear Editor,In ref.we present an efficient full-path optical calculation by using the Bluestein method.A real optical apparatus for laser processing,imaging,or optical tweezing normally involves diverse optical lenses with different physical and numerical apertures(NA).In such applications,the optical path is usually tortuous and long.To assist in the design,evaluation,and alignment of optical instruments,it is advantageous to retrieve the optical field in an arbitrary position along the entire optical path,which is termed the full-path calculation in our paper,with sufficient accuracy and efficiency.In particular,high flexibility is required to accommodate the mismatch between optical apertures of different components in the optical path.We present a fullpath optical calculation method by adopting the Bluestein method to address this realistic demand.

Multilayered skyscraper microchipsfabricated by hybrid “all-in-one”femtosecond laser processing

Multilayered microfluidic channels integrated with functional microcomponents are the general trend of future biochips,which is similar to the history of Si-integrated circuits from the planer to the three-dimensional(3D)configuration,since they offer miniaturization while increasing the integration degree and diversifying the applications in the reaction,catalysis,and cell cultures.In this paper,an optimized hybrid processing technology is proposed to create true multilayered microchips,by which“all-in-one”3D microchips can be fabricated with a successive procedure of 3D glass micromachining by femtosecond-laser-assisted wet etching(FLAE)and the integration of microcomponents into the fabricated microchannels by two-photon polymerization(TPP).To create the multilayered microchannels at different depths in glass substrates(the top layer was embedded at 200μm below the surface,and the underlying layers were constructed with a 200-μm spacing)with high uniformity and quality,the laser power density(13~16.9 TW/cm^(2))was optimized to fabricate different layers.To simultaneously complete the etching of each layer,which is also important to ensure the high uniformity,the control layers(nonlaser exposed regions)were prepared at the upper ends of the longitudinal channels.Solvents with different dyes were used to verify that each layer was isolated from the others.The high-quality integration was ensured by quantitatively investigating the experimental conditions in TPP,including the prebaking time(18~40 h),laser power density(2.52~3.36 TW/cm2)and developing time(0.8~4 h),all of which were optimized for each channel formed at different depths.Finally,the eightlayered microfluidic channels integrated with polymer microstructures were successfully fabricated to demonstrate the unique capability of this hybrid technique.