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Cross-scale self-similar hierarchical micro–nano structures in living systems often provide unique features on surfaces and serve as inspiration sources for artificial materials or devices. For instance, a highly self-similar structure often has a higher fractal dimension and, consequently, a larger active surface area; hence, it would have a super surface performance compared to its peer. However, artificial self-similar surfaces with hierarchical micro–nano structures and their application development have not yet received enough attention. Here, by introducing solvent-assisted UV-lasering, we establish an elegant approach to fabricate self-similar hierarchical micro–nano structures on silicon. The self-similar structure exhibits a super hydrophilicity, a high light absorbance (>90%) in an ultra-broad spectrum (200–2500 nm), and an extraordinarily high efficiency in heat transfer. Through further combinations with other techniques, such surfaces can be used for capillary assembling soft electronics, surface self-cleaning, and so on. Furthermore, such an approach can be transferred to other materials with minor modifications. For instance, by doping carbon in polymer matrix, a silicone surface with hierarchical micro–nano structures can be obtained. By selectively patterning such hierarchical structures, we obtained an ultra-high sensitivity bending sensor. We believe that such a fabrication technique of self-similar hierarchical micro–nano structures may encourage researchers to deeply explore the unique features of functional surfaces with such structures and to further discover their potentials in various applications in diverse directions.

Micro/nano hierarchical structures could endow materials with various surface functions. However, the multilayer and multiscale characteristics of micro/nano hierarchical structures bring difficulties for their one step and controllable fabrication. Accordingly, based on tip-based fabrication techniques, this study proposed a micro-amplitude vibration-assisted scratching method by introducing a periodic backward displacement into the conventional scratching process, which enabled the synchronous creation of the microscale V-groove and nanoscale ripples, i.e. a typical micro/nano hierarchical structure. The experiments and finite element modeling were employed to explore the formation process and mechanism of the micro/nano hierarchical structures. Being different from conventional cutting, this method was mainly based on the plow mechanism, and it could accurately replicate the shape of the indenter on the material surface. The microscale V-groove was formed due to the scratching action, and the nanoscale ripple was formed due to the extrusion action of the indenter on the microscale V-groove’s surface. Furthermore, the relationships between the processing parameters and the dimensions of the micro/nano hierarchical structures were established through experiments, and optimized processing parameters were determined to achieve regular micro/nano hierarchical structures. By this method, complex patterns constructed by various micro/nano hierarchical structures were fabricated on both flat and curved surfaces, achieving diverse surface structural colors. A micro-amplitude vibration-assisted scratching method was proposed. One step and controllable fabrication of microscale V-groove and nanoscale ripples was achieved. The effects of processing parameters on the resultant structures were explored. Relationships between processing parameters and dimensions of the resultant structures were established. Complex patterns were fabricated on flat and curved surfaces, achieving various structural colors.

The failure of orthopedic and dental implants is mainly caused by biomaterial-associated infections and poor osseointegration. Surface modification of biomedical materials plays a significant role in enhancing osseointegration and anti-bacterial infection. In this work, a non-linear relationship between the micro/nano surface structures and the femtosecond laser processing parameters was successfully established based on an artificial neural network. Then a controllable functional surface with silver nanoparticles (AgNPs) to was produced to improve the cytocompatibility and antibacterial properties of biomedical titanium alloy. The surface topography, wettability, and Ag + release were carefully investigated. The effects of these characteristics on antibacterial activity and cytocompatibilty were also evaluated. Results show that the prepared surface is hydrophobic, which can prevent the burst release of Ag + in the initial stage. The prepared surface also shows both good cytocompatibility toward the murine calvarial preosteoblasts MC3T3-E1 cells (derived from Mus musculus (mouse) calvaria) and good antibacterial effects against Gram-negative ( E. coli ) and Gram-positive ( S. aureus ) bacteria, which is caused by the combined effect of appropriate micro/nano-structured feature and reasonable Ag + release rate. We do not only clarify the antibacterial mechanism but also demonstrate the possibility of balancing the antibacterial and osteointegration-promoting properties by micro/nano-structures. The reported method offers an effective strategy for the patterned surface modification of implants. Graphical Abstract

Flexible enzyme-free glucose sensors have attracted widespread attention due to their importance and potential applications in clinical diagnosis, flexible wearable devices, and implanted devices in vivo. At present, there are still major problems in fabricating flexible enzyme-free glucose sensors with low detection limits, high stability, and high sensitivity at low cost, hindering their practical application. Here, we report a facile strategy for the fabrication of flexible non-enzymatic glucose sensors using ginkgo leaf as a template. NiO film and PEDOT:PSS composite film were deposited on the surface of the ginkgo leaf induced micro-nano hierarchical structure as a sensitive layer and a conductive layer, respectively. The as-prepared, flexible, enzyme-free glucose sensor exhibited excellent electrochemical performance toward glucose oxidation with a sensitivity of 0.7413 mA·mM−1/cm−2, an operating voltage of 0.55 V, a detection limit of 0.329 μM, and good anti-interference. Due to the simple fabrication process and performance reliability, the novel flexible enzyme-free glucose sensor is an attractive candidate for next generation wearable and implantable non-enzymatic glucose diagnostic devices.

Broadband antireflective surface technology constitutes a crucial technique in optoelectronic devices, playing a key role in reducing optical losses. Ultrafast laser processing provides a flexible route for fabricating micro-nano structures on metallic surfaces because it enables efficient fabrication, high spatial resolution, and minimal chemical consumption. This study uses a variable-angle scanning strategy to texture the copper surface, produce a series of antireflection arrayed micro-nano structures, and study the spectral reflectance characteristics of the copper surface. The results exhibit that 90° orthogonal scanning favors the formation of an arrayed microcone structure, which shows lower reflectance than the non-orthogonal scanning strategies in the 200–1300 nm band, with a minimum reflectance of 0.94%. The 60° and 45° cross-scanning based on the non-orthogonal strategy favors the formation of microcavity structures, and shows low reflectance in the 1300–2500 nm band, with the maximum reflectance remaining below 5%. Laser-induced periodic surface structures (LIPSS) are observed on the structures fabricated by all strategies. This work demonstrates that the scanning angle itself can be used to switch the dominant surface morphology and thereby tailor the spectral antireflection response, and lies in establishing a clear processing–structure–spectral response relationship for copper surfaces, which provides a designable route for wavelength-selective optical absorption in photothermal conversion, infrared detection, and sensing applications.

An easy-to-implement method by which to fabricate superhydrophobic surfaces inspired taro leaf was successfully applied on 316L stainless steel via combining nanosecond laser (NL) processing and spin-coating techniques. The laser-textured surface composed of microscale frameworks and central bumps was fabricated by NL processing based on properly designed biomimetic patterns, and a layer of nanoscale carbon black/polydimethylsiloxane (CB/PDMS) particles was covered on it by spin-coating. The effect of pattern parameters (i.e., the inscribed circle radius of framework and the radius of central bump) on wettability of biomimetic surface was investigated. All as-prepared biomimetic surfaces with micro-nano hierarchical structures showed excellent superhydrophobicity with the water contact angle of ∼155° and contact angle hysteresis of ∼2°. By comparing the untreated surface, the wetting behavior and evaporation mode of the biomimetic surface occurred an obvious transformation. Meanwhile, experiments indicated that the biomimetic surface not only had liquid-repelling and self-cleaning functions, but also maintained remarkable mechanical robustness and superhydrophobic durability. The method is efficient for fabricating biomimetic superhydrophobic surfaces applied to liquid-repelling, evaporation-transforming and self-cleaning fields.

Mitigating the optical reflection of aluminum alloy over a broad spectral range from 0.45 μ m to 15 μ m is vital for many applications. This can be realized by introducing efficient light-absorbing textured surfaces via femtosecond laser surface processing. However, a clear analysis of antireflection performance has not been reported yet. This paper proposes a numerical model of anti-reflective structures is proposed based on SEM and EDS characterization. Multiple anti-reflective mechanisms were revealed intuitively through FDTD simulation.

Surface topography acts as an irreplaceable role in the long‐term success of intraosseous implants. In this study, we prepared the hierarchical micro/nano topography using selective laser melting combined with alkali heat treatment (SLM‐AHT) and explored the underlying mechanism of SLM‐AHT surface‐elicited osteogenesis. Our results show that cells cultured on SLM‐AHT surface possess the largest number of mature FAs and exhibit a cytoskeleton reorganization compared with control groups. SLM‐AHT surface could also significantly upregulate the expression of the cell adhesion‐related molecule p‐FAK, the osteogenic differentiation‐related molecules RUNX2 and OCN as well as the mTORC2 signalling pathway key molecule Rictor. Notably, after the knocked‐down of Rictor, there were no longer significant differences in the gene expression levels of the cell adhesion‐related molecules and osteogenic differentiation‐related molecules among the three titanium surfaces, and the cells on SLM‐AHT surface failed to trigger cytoskeleton reorganization. In conclusion, the results suggest that mTORC2 can regulate the hierarchical micro/nano topography‐mediated osteogenesis via cell adhesion and cytoskeletal reorganization.

A large number of studies have attempted to fabricate superhydrophobic surface with micro-nano hierarchical structure on the surface of polytetrafluoroethylene (PTFE). However, the tough crystalline structure and extremely high viscosity of PTFE bring great challenges in the practical processing and industries application. In this study, we aim to fabricate superhydrophobic surface with micro-nano hierarchical structure on PTFE/graphite composite surface using hot embossing process. The as-fabricated superhydrophobic surface possesses micro-scale protrusion, nano-scale structures, and submicron fibers between the protrusions. The formation mechanism of the micro-nano hierarchical structure was analyzed numerically, and the superhydrophobicity of the embossed surfaces under different conditions was investigated experimentally. The superhydrophobic performance is fully realized at the process condition of temperature range of 210 ~ 250℃ and an embossing time of above 5 min. The impact of hot embossing process conditions on the height of protrusion and static contact angle was also analyzed. The maximum static contact angle was measured as 160.7°. Subsequently, by comparing the impact dynamics of droplets on PTFE and PTFE/ graphite composite surfaces, it is verified that PTFE/ graphite composite shows superior hydrophobicity.

Learning hydrophobic phenomena from nature is always a promising approach to design the superhydrophobic surface. Purple orchid leaf which processes superhydrophobicity is an ideal plant model, and through mimicking its structure, the surface with excellent hydrophobicity is able to be obtained. However, the unclear of the diversity in wettability during the different vegetation stages and the absence of its relation to the surface morphology limits the further enhancement of the inspired structure. Here, we analyze the wettability difference as the leaf grows from tender to mature and then to senescent. Combining with the variation of surface morphology and chemical composition, the well-developed micro-scale basic unit bumps with dense nano-scale waxy layer on the surface are proven to be responsible for the best hydrophobicity of the mature leaf. The presence of the undeveloped or damaged micro-nano hierarchical structure reduces the formation of air pockets at the interface, leading to the decrease of the wettability for leaves at other stages. Moreover, by fabricating artificial leaves, the nano-waxy layer is proved to be more effective than that of the micro-bumps on the surface wettability. The results of study are of a great significance for guiding the design and fabrication of plant-inspired bionic superhydrophobic surface.