Femtosecond laser writing of lithium niobate ferroelectric nanodomains.

Lithium niobate (LiNbO3) is viewed as a promising material for optical communications and quantum photonic chips1,2. Recent breakthroughs in LiNbO3 nanophotonics have considerably boosted the development of high-speed electro-optic modulators3-5, frequency combs6,7 and broadband spectrometers8. However, the traditional method of electrical poling for ferroelectric domain engineering in optic9-13, acoustic14-17 and electronic applications18,19 is limited to two-dimensional space and micrometre-scale resolution. Here we demonstrate a non-reciprocal near-infrared laser-writing technique for reconfigurable three-dimensional ferroelectric domain engineering in LiNbO3 with nanoscale resolution. The proposed method is based on a laser-induced electric field that can either write or erase domain structures in the crystal, depending on the laser-writing direction. This approach offers a pathway for controllable nanoscale domain engineering in LiNbO3 and other transparent ferroelectric crystals, which has potential applications in high-efficiency frequency mixing20,21, high-frequency acoustic resonators14-17 and high-capacity non-volatile ferroelectric memory19,22.

Large Field-of-View Nonlinear Holography in Lithium Niobate.

A nonlinear holographic technique is capable of processing optical information in the newly generated optical frequencies, enabling fascinating functions in laser display, security storage, and image recognition. One popular nonlinear hologram is based on a periodically poled lithium niobate (LN) crystal. However, due to the limitations of traditional fabrication techniques, the pixel size of the LN hologram is typically several micrometers, resulting in a limited field-of-voew (FOV) of several degrees. Here, we experimentally demonstrate an ultra-high-resolution LN hologram by using the laser poling technique. The minimal pixel size reaches 200 nm, and the FOV is extended above 120° in our experiments. The image distortions at large view angles are effectively suppressed through the Fourier transform. The FOV is further improved by combining multiple diffraction orders of SH fields. The ultimate FOV under our configuration is decided by a Fresnel transmission. Our results pave the way for expanding the applications of nonlinear holography to wide-view imaging and display.

Tip-induced nanoscale domain engineering in x-cut lithium niobate on insulator.

Nanodomain engineering in lithium niobate on insulator (LNOI) is critical to realize advanced photonic circuits. Here, we investigate the tip-induced nanodomain formation in x-cut LNOI. The effective electric field exhibits a mirror symmetry, which can be divided into preceding and sequential halves according to the tip movement. Under our configuration, the preceding electric field plays a decisive role rather than the sequential one as in previous reports. The mechanism is attributed to the screening field formed by the preceding field counteracting the effect of the subsequent one. In experiment, we successfully fabricate nanodomain dots, lines, and periodic arrays. Our work offers a useful approach for nanoscale domain engineering in x-cut LNOI, which has potential applications in integrated optoelectronic devices.

Fabrication of 100-nm-period domain structure in lithium niobate on insulator.

Lithium niobate on insulator (LNOI) is a powerful platform for integrated photonic circuits. Recently, advanced applications in nonlinear and quantum optics require to controllably fabricate nano-resolution domain structures in LNOI. Here, we report on the fabrication of stable domain structures with sub-100 nm feature size through piezoelectric force microscopy (PFM) tip poling in a z-cut LNOI. In experiment, the domain dot with an initial diameter of 80 nm and the domain line with an initial width of 50 nm can survive after a storage of more than 3 months. Particularly, we demonstrate the successful fabrication of 1D stable domain array with a period down to 100 nm and a duty cycle of ∼50%. Our method paves the way to precisely manipulate frequency conversion and quantum entanglement on an LNOI chip.

Reconfigurable, Reversible, and Redefinable Deformation of GO Based on Quantum-Confined-Superfluidics Effect.

Graphene oxide (GO) films with natural "quantum-confined-superfluidics" (QSF) channels for moisture actuation have emerged as a smart material for actuators and soft robots. However, programming the deformation of GO by engineering QSF nanochannels around 1 nm is extremely challenging. Herein, we report the reconfigurable, reversible, and redefinable deformation of GO under moisture actuation by tailoring QSF channels via moisture-assisted strain-induced wrinkling (MSW). The shape fixity ratio of a general GO film can reach ∼84% after the MSW process, and the shape recovery ratio is ∼83% at room temperature under moisture actuation. The flexible shaping and deformation abilites, as well as the self-healing property of GO make it possible to fabricate soft robots using GO. Besides, as a proof-of-concept, passive electronics and soft robots capable of crawling, turning, switching circuit, and automatic somersault are demonstrated. With unique shaping and deformation abilities, GO may bring great implications for future soft robotics.

Facile fabrication of flexible graphene FETs by sunlight reduction of graphene oxide.

We reported here a facile fabrication of flexible graphene-based field effect transistors (FETs) by sunlight reduction of graphene oxide (GO) as channel material. As a mask-free and chemical-free method, sunlight photoreduction of GO without the use of any complex equipments is simple and green. The resultant FET demonstrated excellent electrical properties (e.g., an optimized Ion/Ioff ratio of 111, hole mobility of 0.17 cm2 V-1 s-1), revealing great potential for development of flexible microelectrics. Additionally, since the reduced GO channel could be fabricated by sunlight treatment between two pre-patterned electrodes, the process features post-fabrication capability, which makes it possible to integrate graphene-based devices with given device structures.

A high-performance organic thin-film transistor with Parylene/PMMA bilayer insulation based on P3HT.

This work introduces a pioneering approach in the development of organic thin-film transistors (OTFTs), featuring a double-layer dielectric structure that combines poly(para-xylylene)s (Parylene) and poly(methyl methacrylate) (PMMA) to leverage the high insulation properties and high surface polarity of Parylene with the low insulation properties and low surface polarity of PMMA. This combination results in devices that showcase significantly enhanced electrical performance, including superior charge carrier mobility, increased current on/off ratios, and greater transconductance. Utilizing poly(3-hexylthiophene) (P3HT) for the active layer, the study demonstrates the advantage of the dual dielectric layers in minimizing hysteresis in the transfer curve, thereby facilitating the systematic growth of the organic active layer and enhancing electrical conductivity over single-layer alternatives. The superior performance of the Parylene/PMMA double-layer insulating structure opens new avenues for the advancement of organic electronics, presenting methodologies for performance optimization and expanding the application spectrum of OTFTs.

Quantum-Confined-Superfluidics-Enabled Multiresponsive MXene-Based Actuators.

MXene, renowned for its natural "quantum-confined-superfluidic" (QSF) channels, demonstrates superior electrical/thermal conductivity, favorable hydrophilicity, and remarkable mechanical strength, rendering it an ideal candidate for multiresponsive actuators, which are promising for soft electronics and robots. Currently, most MXene-based actuators are mainly prepared by combining an active layer and an inner layer, with only a few utilizing regulated QSF channels. However, tailoring QSF channels for multiresponsive actuators is extremely challenging. Herein, we introduce a multiresponsive graphene oxide (GO)&Fe3O4/MXene actuator that can respond to humidity, light, heat, electricity, and magnetic fields by constructing asymmetric QSF channels. The asymmetric water adsorption, transportation, and desorption behaviors, controlled by the different QSF channels between the GO&Fe3O4 layer and the MXene layer, enable the multiresponsiveness of the actuator. As proof-of-concept demonstrations, several smart devices, such as a bionic crab-like crawler, a transporting flower robot, and a smart gripper, are prepared, holding great potential for advancing future soft robotics.

Dissolving Microneedles Loaded with Gestodene: Fabrication and Characterization In Vitro and In Vivo.

Background: Gestodene (GEST) is widely used in female contraception. It is currently being used as an oral contraceptive. However, unfortunately, oral contraceptives are often associated with several bothersome side effects and poor compliance. Therefore, a sustained delivery system for GEST to overcome these shortcomings is highly desirable. Objectives: The present study successfully developed a kind of novel dissolving microneedles (DMNs) with a potential for sustained release and a minimally invasive intradermal treatment of GEST. Methods: The dissolving microneedles containing GEST were fabricated using polyvinylpyrrolidone as the base material. The characteristics in vitro and pharmacokinetics in vivo of GEST-loaded DMNs were investigated. Results: The results showed that the microneedle could pierce the porcine skin and release the drug at an average dose of 20µg/cm2 daily for seven days. The pharmacokinetic experiment of the microneedles indicated that the plasma level of GEST in rats increased with increasing drug dosage, and the plasma drug concentration-time curves were much flatter compared with subcutaneous injection and oral administration. In addition, no cutaneous irritation was observed. Conclusions: GEST-loaded DMNs may be a promising intradermal sustained delivery system for contraceptive use.

Isolation and characterization of algicidal bacteria from freshwater aquatic environments in China.

Algicidal bacteria can inhibit the growth of algae or lyse algal cells, thus playing roles in shaping aquatic microbial communities and maintaining the functions of aquatic ecosystems. Nevertheless, our understanding of their diversities and distributions remains limited. In this study, we collected water samples from 17 freshwater sites in 14 cities in China and screened a total of 77 algicidal bacterial strains using several prokaryotic cyanobacteria and eukaryotic algae as target strains. According to their target-specificities, these strains were classified into three subgroups, cyanobacterial algicidal bacteria, algal algicidal bacteria, and broad-target algicidal bacteria, each displaying distinctive compositions and geographical distribution patterns. They are assigned to Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes bacterial phyla, of which Pseudomonas and Bacillus are the most abundant gram-negative and gram-positive genus, respectively. A number of bacterial strains, such as Inhella inkyongensis and Massilia eburnean, are suggested as new algicidal bacteria. The diverse taxonomies, algal-inhibiting abilities and distributions of these isolates have suggested that there are rich algicidal bacterial resources in these aquatic environments. Our results provide new microbial resources for algal-bacterial interaction studies, and shed new insights into how algicidal bacteria can be used in the control of harmful algal blooms, as well as in algal biotechnology.

iTRAQ-Based Quantitative Proteomic Analysis of Arthrobacter simplex in Response to Cortisone Acetate and Its Mutants with Improved Δ1-Dehydrogenation Efficiency.

Arthrobacter simplex is extensively used for cortisone acetate (CA) biotransformation in industry, but the Δ1-dehydrogenation molecular fundamental remains unclear. Herein, the comparative proteome revealed several proteins with the potential role in this reaction, which were mainly involved in lipid or amino acid transport and metabolism, energy production and conversion, steroid degradation, and transporter. The influences of six proteins were further confirmed, where pps, MceGA, yrbE4AA, yrbE4BA, and hyp2 showed positive impacts, while hyp1 exhibited a negative effect. Additionally, KsdD5 behaved as the best catalytic enzyme. By the combined manipulation in multiple genes under the control of a stronger promoter, an optimal strain with better catalytic enzyme activity, substrate transportation, and cell stress tolerance was created. After biotechnology optimization, the production peak and productivity were, respectively, boosted by 4.1- and 4.0-fold relative to the initial level. Our work broadens the understanding of the Δ1-dehydrogenation mechanism, also providing effective strategies for excellent steroid-transforming strains.

PPARδ inhibition blocks the induction and function of tumor-induced IL-10+ regulatory B cells and enhances cancer immunotherapy.

IL-10+ regulatory B cells (Bregs) play a significant role in cancer immunotherapy and their presence is an indicator of negative outcome. We found that PPARδ is significantly upregulated in tumor-induced IL-10+ Bregs with a phenotype of CD19+CD24hiIgDlo/-CD38lo or CD19+CD24hiIgDlo/-CD38hi in both mice and humans, and the level of PPARδ expression was correlated with their potential to produce IL-10 and to inhibit T cell activation. Genetic inactivation of PPARδ in B cells impaired the development and function of IL-10+ B cells, and treatment with PPARδ inhibitor diminished the induction of IL-10+ Bregs by tumor and CD40 engagement. Importantly, immunotherapy with anti-CD40 or anti-PD1 antibody achieved a markedly improved outcome in tumor-bearing mice with PPARδ deficiency in B cells or treated with PPARδ inhibitor. This study shows that PPARδ is required for the development and function of IL-10+ Bregs, providing a new and effective target for selectively blocking Bregs and improving antitumor immunotherapy.

Femtosecond-laser-assisted high-aspect-ratio nanolithography in lithium niobate.

We report the successful fabrication of high-aspect-ratio lithium niobate (LN) nanostructures by using femtosecond-laser-assisted chemical etching. In this technique, a 1 kHz femtosecond laser is first used to induce local modifications inside the LN crystal. Then, selective chemical wet etching is conducted using a buffered oxide etch (BOE) solution. The etching rate in the laser-modified area reaches 2 µm h-1, which is enhanced by a factor of ∼660 in comparison to previous reports without laser irradiation. Such high selectivity in chemical etching helps realize high-performance maskless nanolithography in lithium niobate. In the experiment, we have fabricated high-quality LN nanohole arrays. The nanohole size reaches ∼100 nm and its aspect ratio is above 40 : 1. The minimal period of the LN hole array is 300 nm. Our work paves a way to fabricate LN nano-integrated devices for advanced optic and electronic applications.

Laser nanoprinting of 3D nonlinear holograms beyond 25000 pixels-per-inch for inter-wavelength-band information processing.

Nonlinear optics provides a means to bridge between different electromagnetic frequencies, enabling communication between visible, infrared, and terahertz bands through χ(2) and higher-order nonlinear optical processes. However, precisely modulating nonlinear optical waves in 3D space remains a significant challenge, severely limiting the ability to directly manipulate optical information across different wavelength bands. Here, we propose and experimentally demonstrate a three-dimensional (3D) χ(2)-super-pixel hologram with nanometer resolution in lithium niobate crystals, capable of performing advanced processing tasks. In our design, each pixel consists of properly arranged nanodomain structures capable of completely and dynamically manipulating the complex-amplitude of nonlinear waves. Fabricated by femtosecond laser writing, the nonlinear hologram features a pixel diameter of 500 nm and a pixel density of approximately 25000 pixels-per-inch (PPI), reaching far beyond the state of the art. In our experiments, we successfully demonstrate the novel functions of the hologram to process near-infrared (NIR) information at visible wavelengths, including dynamic 3D nonlinear holographic imaging and frequency-up-converted image recognition. Our scheme provides a promising nano-optic platform for high-capacity optical storage and multi-functional information processing across different wavelength ranges.

Heterogeneous self-healing assembly of MXene and graphene oxide enables producing free-standing and self-reparable soft electronics and robots.

Self-healing materials (SHMs) with unique mechanical and electronic properties are promising for self-reparable electronics and robots. However, the self-healing ability of emerging two-dimensional (2D) materials, for instance, MXenes, has not been systematically investigated, which limits their applications in self-healing electronics. Herein, we report the homogeneous self-healing assembly (homo-SHA) of MXene and the heterogeneous self-healing assembly (hetero-SHA) of MXene and graphene oxide (GO) under moisture treatments. The self-healing mechanism has been attributed to the hydration induced interlayer swelling of MXene and GO and the recombination of hydrogen bond networks after water desorption. The multiform hetero-SHA of MXene and GO not only enables facile fabrication of free-standing soft electronics and robots, but also endows the resultant devices with damage-healing properties. As proof-of-concept demonstrations, free-standing soft electronic devices including a generator, a humidity sensor, a pressure sensor, and several robotic devices have been fabricated. The hetero-SHA of MXene and GO is simple yet effective, and it may pioneer a new avenue to develop miniature soft electronics and robots based on 2D materials.

Bioinspired Soft Robots Based on the Moisture-Responsive Graphene Oxide.

Graphene oxide (GO), which has many oxygen functional groups, is a promising candidate for use in moisture-responsive sensors and actuators due to the strong water-GO interaction and the ultrafast transport of water molecules within the stacked GO sheets. In the last 5 years, moisture-responsive actuators based on GO have shown distinct advantages over other stimuli-responsive materials and devices. Particularly, inspired by nature organisms, various moisture-enabled soft robots have been successfully developed via rational assembly of the GO-based actuators. Herein, the milestones in the development of moisture-responsive soft robots based on GO are summarized. In addition, the working mechanisms, design principles, current achievement, and prospects are also comprehensively reviewed. In particular, the GO-based soft robots are at the forefront of the advancement of automatable smart devices.

Quasi-phase-matching-division multiplexing holography in a three-dimensional nonlinear photonic crystal.

Nonlinear holography has recently emerged as a novel tool to reconstruct the encoded information at a new wavelength, which has important applications in optical display and optical encryption. However, this scheme still struggles with low conversion efficiency and ineffective multiplexing. In this work, we demonstrate a quasi-phase-matching (QPM) -division multiplexing holography in a three-dimensional (3D) nonlinear photonic crystal (NPC). 3D NPC works as a nonlinear hologram, in which multiple images are distributed into different Ewald spheres in reciprocal space. The reciprocal vectors locating in a given Ewald sphere are capable of fulfilling the complete QPM conditions for the high-efficiency reconstruction of the target image at the second-harmonic (SH) wave. One can easily switch the reconstructed SH images by changing the QPM condition. The multiplexing capacity is scalable with the period number of 3D NPC. Our work provides a promising strategy to achieve highly efficient nonlinear multiplexing holography for high-security and high-density storage of optical information.

Programmable deformation of patterned bimorph actuator swarm.

Graphene-based actuators featuring fast and reversible deformation under various external stimuli are promising for soft robotics. However, these bimorph actuators are incapable of complex and programmable 3D deformation, which limits their practical application. Here, inspired from the collective coupling and coordination of living cells, we fabricated a moisture-responsive graphene actuator swarm that has programmable shape-changing capability by programming the SU-8 patterns underneath. To get better control over the deformation, we fabricated SU-8 micropattern arrays with specific geometries and orientations on a continuous graphene oxide film, forming a swarm of bimorph actuators. In this way, predictable and complex deformations, including bending, twisting, coiling, asymmetric bending, 3D folding, and combinations of these, have been achieved due to the collective coupling and coordination of the actuator swarm. This work proposes a new way to program the deformation of bilayer actuators, expanding the capabilities of existing bimorph actuators for applications in various smart devices.

Nacre-inspired moisture-responsive graphene actuators with robustness and self-healing properties.

Moisture-responsive actuators based on graphene oxide (GO) have attracted intensive research interest in recent years. However, current GO actuators suffer from low mechanical strength. Inspired by the robustness of nacre's structure, moisture-responsive actuators with high mechanical strength and self-healing properties were successfully developed based on GO and cellulose fiber (CF) hybrids. The hybrid paper demonstrated significantly improved tensile strength, ∼20 times higher than that of pure GO paper, and self-healing properties. A broken paper can be well cured under moist conditions, and the mechanical properties of the self-healed hybrid paper can still maintain similar tensile strength to the pristine one. After controllable ultraviolet light photoreduction treatment, a hybrid paper with a photoreduction gradient along the normal direction was prepared, which can act as a moisture-responsive actuator. A maximum bending curvature of ∼1.48 cm-1 can be achieved under high relative humidity (RH = 97%). As a proof-of-concept, a butterfly-like actuator that can deform itself with moisture actuation was demonstrated. Our approach may pave a new way for designing robust and self-healable graphene actuators.

Quantum-Confined-Superfluidics-Enabled Moisture Actuation Based on Unilaterally Structured Graphene Oxide Papers.

The strong interaction between graphene oxides (GO) and water molecules has trigged enormous research interest in developing GO-based separation films, sensors, and actuators. However, sophisticated control over the ultrafast water transmission among the GO sheets and the consequent deformation of the entire GO film is still challenging. Inspired from the natural "quantum-tunneling-fluidics-effect," here quantum-confined-superfluidics-enabled moisture actuation of GO paper by introducing periodic gratings unilaterally is reported. The folded GO nanosheets that act as quantum-confined-superfluidics channels can significantly promote water adsorption, enabling controllable and sensitive moisture actuation. Water-adsorption-induced expansion along and against the normal direction of a GO paper is investigated both theoretically and experimentally. Featuring state-of-the-art of ultrafast response (1.24 cm-1 s-1 ), large deformation degree, and complex and predictable deformation, the smart GO papers are used for biomimetic mini-robots including a creeping centipede and a smart leaf that can catch a living ladybug. The reported method is simple and universal for 2D materials, revealing great potential for developing graphene-based smart robots.