Using angle-resolved photoemission spectroscopy (ARPES), we revealed the surface electronic structure and superconducting gap of (Li 0.8 Fe 0.2 )OHFeSe, an intercalated FeSe-derived superconductor without antiferromagnetic phase or Fe-vacancy order in the FeSe layers, and with a superconducting transition temperature (T c ) ∼ 40 K. We found that (Li 0.8 Fe 0.2 )OH layers dope electrons into FeSe layers. The electronic structure of surface FeSe layers in (Li 0.8 Fe 0.2 )OHFeSe resembles that of Rb x Fe 2−y Se 2 except that it only contains half of the carriers due to the polar surface, suggesting similar quasiparticle dynamics between bulk (Li 0.8 Fe 0.2 )OHFeSe and Rb x Fe 2−y Se 2 . Superconducting gap is clearly observed below T c , with an isotropic distribution around the electron Fermi surface. Compared with A x Fe 2−y Se 2 (A=K, Rb, Cs, Tl/K), the higher T c in (Li 0.8 Fe 0.2 )OHFeSe might be attributed to higher homogeneity of FeSe layers or to some unknown roles played by the (Li 0.8 Fe 0.2 )OH layers.

Swarming micro/nanomotors can self-organize into cohesive groups to execute cooperative tasks. To date, research work has focused on the construction of egalitarian microswarms composed of similar individuals. The construction and collective behaviors of hierarchical leaderfollower-like microswarms are demonstrated. By inducing converging electrohydrodynamic flows under an AC electric field, dielectric microparticles with different sizes and dielectric properties can hierarchically self-organize into leader-follower-like microswarms under attractive electrohydrodynamic interactions, and show novel emergent collective behaviors. First, different from immobile single constituents or egalitarian clusters, the hierarchical microswarms autonomously move with tunable speed. Second, they exhibit multimode collective photoresponses emerging from different behaviors of the constituents in response to light signals. With a vertical UV signal, the photoresponsive followers tend to surround the leader and stop the microswarm. In response to sidewise UV signals, the constituents with stronger phototaxis would migrate to the position away from light stimuli, and thus the microswarms reorient parallel/antiparallel to the light direction and perform collective positive/negative phototaxis. Due to differential roles and huge design spaces of constituents, the hierarchical microswarms are envisioned to possess merits of high-efficiency, multiresponsiveness, and multifunctions, and may serve as intelligent micro/nanorobot systems for biomedicine and microengineering.

Micro/nano structures have unique optical, electrical, magnetic, and thermal properties. Studies on the preparation of micro/nano structures are of considerable research value and broad development prospects. Several micro/nano structure preparation techniques have already been developed, such as photolithography, electron beam lithography, focused ion beam techniques, nanoimprint techniques. However, the available geometries directly implemented by those means are limited to the 2D mode. Laser machining, a new technology for micro/nano structural preparation, has received great attention in recent years for its wide application to almost all types of materials through a scalable, one-step method, and its unique 3D processing capabilities, high manufacturing resolution and high designability. In addition, micro/nano structures prepared by laser machining have a wide range of applications in photonics, Surface plasma resonance, optoelectronics, biochemical sensing, micro/nanofluidics, photofluidics, biomedical, and associated fields. In this paper, updated achievements of laser-assisted fabrication of micro/nano structures are reviewed and summarized. It focuses on the researchers’ findings, and analyzes materials, morphology, possible applications and laser machining of micro/nano structures in detail. Seven kinds of materials are generalized, including metal, organics or polymers, semiconductors, glass, oxides, carbon materials, and piezoelectric materials. In the end, further prospects to the future of laser machining are proposed.