Femtosecond Laser Fabrication of Three-Dimensional Bubble-Propelled Microrotors for Multicomponent Mechanical Transmission.

Inspired by the reverse thrust generated by fuel injection, micromachines that are self-propelled by bubble ejection are developed, such as microrods, microtubes, and microspheres. However, controlling bubble ejection sites to build micromachines with programmable actuation and further enabling mechanical transmission remain challenging. Here, bubble-propelled mechanical microsystems are constructed by proposing a multimaterial femtosecond laser processing method, consisting of direct laser writing and selective laser metal reduction. The polymer frame of the microsystems is first printed, followed by the deposition of catalytic platinum into the desired local site of the microsystems by laser reduction. With this method, a variety of designable microrotors with selective bubble ejection sites are realized, which enable excellent mechanical transmission systems composed of single and multiple mechanical components, including a coupler, a crank slider, and a crank rocker system. We believe the presented bubble-propelled mechanical microsystems could be extended to applications in microrobotics, microfluidics, and microsensors.

Rapid and Multimaterial 4D Printing of Shape-Morphing Micromachines for Narrow Micronetworks Traversing.

Micromachines with high environmental adaptability have the potential to deliver targeted drugs in complex biological networks, such as digestive, neural, and vascular networks. However, the low processing efficiency and single processing material of current 4D printing methods often limit the development and application of shape-morphing micromachines (SMMs). Here, two 4D printing strategies are proposed to fabricate SMMs with pH-responsive hydrogels for complex micro-networks traversing. On the one hand, the 3D vortex light single exposure technique can rapidly fabricate a tubular SMM with controllable size and geometry within 0.1 s. On the other hand, the asymmetric multimaterial direct laser writing (DLW) method is used to fabricate SMMs with designable 3D structures composed of hydrogel and platinum nanoparticles (Pt NPs). Based on the presence of ferroferric oxide (Fe3 O4 ) and Pt NPs in the SMMs, efficient magnetic, bubble, and hybrid propulsion modes are achieved. Finally, it is demonstrated that the spatial shape conversion capabilities of these SMMs can be used for narrow micronetworks traversing, which will find potential applications in targeted cargo delivery in microcapillaries.

Light-triggered multi-joint microactuator fabricated by two-in-one femtosecond laser writing.

Inspired by the flexible joints of humans, actuators containing soft joints have been developed for various applications, including soft grippers, artificial muscles, and wearable devices. However, integrating multiple microjoints into soft robots at the micrometer scale to achieve multi-deformation modalities remains challenging. Here, we propose a two-in-one femtosecond laser writing strategy to fabricate microjoints composed of hydrogel and metal nanoparticles, and develop multi-joint microactuators with multi-deformation modalities (>10), requiring short response time (30 ms) and low actuation power (<10 mW) to achieve deformation. Besides, independent joint deformation control and linkage of multi-joint deformation, including co-planar and spatial linkage, enables the microactuator to reconstruct a variety of complex human-like modalities. Finally, as a proof of concept, the collection of multiple microcargos at different locations is achieved by a double-joint micro robotic arm. Our microactuators with multiple modalities will bring many potential application opportunities in microcargo collection, microfluid operation, and cell manipulation.

Robust Helical Dichroism on Microadditively Manufactured Copper Helices via Photonic Orbital Angular Momentum.

Three-dimensional chiral metallic metamaterials have already attracted extensive attention in the wide research fields of chiroptical responses. These artificial chiral micronanostructures, possessing strong chiroptical signals, show huge significance in next-generation photonic devices and chiroptical spectroscopy techniques. However, most of the existing chiral metallic metamaterials are designed for generating chiroptical signals dependent on photonic spin angular momentum (SAM). The chiral metallic metamaterials for generating strong chiroptical responses by photonic orbital angular momentum (OAM) remain unseen. In this work, we fabricate copper microhelices with opposite handedness by additively manufacturing and further examine their OAM-dominated chiroptical response: helical dichroism (HD). The chiral copper microhelices exhibit differential reflection to the opposite OAM states, resulting in a significant HD signal (∼50%). The origin of the HD can be theoretically explained by the difference in photocurrent distribution inside copper microhelices under opposite OAM states. Moreover, the additively manufactured copper microhelices possess an excellent microstructural stability under varying annealing temperatures for robust HD responses. Lower material cost and noble-metal-similar optical properties, accompanied with well thermal stability, render the copper microhelices promising metamaterials in advanced chiroptical spectroscopy and photonic OAM engineering.

Temperature-Regulated Bidirectional Capillary Force Self-Assembly of Femtosecond Laser Printed Micropillars for Switchable Chiral Microstructures.

Bottom-up self-assembly is regarded as an alternative way to manufacture series of microstructures in many fields, especially chiral microstructures, which attract tremendous attention because of their optical micromanipulations and chiroptical spectroscopies. However, most of the self-assembled microstructures cannot be tuned after processing, which largely hinders their broad applications. Here, we demonstrate a promising manufacturing strategy for switchable microstructures by combining the flexibility of femtosecond laser printing induced capillary force self-assembly and the temperature-responsive characteristics of smart hydrogels. Through designing asymmetric cross-link density, the printed microarchitectures can be deformed in the opposite direction and assembled into switchable ordered microstructures driven by capillary forces under different temperatures. Finally, the assembled chiral microstructures with switchable opposite handedness are realized, which shows tunable vortical dichroism. The proposed strategy holds potential applications in the fields of chiral photonics, chiral sensing, and so on.

Enhancing the sensitivity for weak radioactive source detection.

Considering the difficulties of the low signal-to-noise ratio in weak radioactive source detections, this study proposes an abandon Gaussian tails method based on the analysis of the characteristic information denoted by the full-energy peak of the gamma spectrum of a gamma-emitting radioactive source. Based on the study of the signal-to-background ratio and the statistical fluctuations in the signal of the weak radioactive source, a factor ζ, incorporating the statistical fluctuations of signal and background and the signal-to-background ratio, is suggested to characterize the sensitivity of a radioactive source detection. When ζ reaches its maximum value, the optimal counting window around the centroid of the full-energy peak can be obtained. To evaluate the effectiveness of the proposed approach, comparisons between the proposed abandon Gaussian tails, the conventional full-energy counting, and other experiential methods were performed. The results show that the sensitivity can be significantly improved. Further, experiments with different intensity of radiation sources and duplicated experiments were conducted to examine the stability of the proposed method.

Environmentally Adaptive Shape-Morphing Microrobots for Localized Cancer Cell Treatment.

Microrobots have attracted considerable attention due to their extensive applications in microobject manipulation and targeted drug delivery. To realize more complex micro-/nanocargo manipulation (e.g., encapsulation and release) in biological applications, it is highly desirable to endow microrobots with a shape-morphing adaptation to dynamic environments. Here, environmentally adaptive shape-morphing microrobots (SMMRs) have been developed by programmatically encoding different expansion rates in a pH-responsive hydrogel. Due to a combination with magnetic propulsion, a shape-morphing microcrab (SMMC) is able to perform targeted microparticle delivery, including gripping, transporting, and releasing by "opening-closing" of a claw. As a proof-of-concept demonstration, a shape-morphing microfish (SMMF) is designed to encapsulate a drug (doxorubicin (DOX)) by closing its mouth in phosphate-buffered saline (PBS, pH ∼ 7.4) and release the drug by opening its mouth in a slightly acidic solution (pH < 7). Furthermore, localized HeLa cell treatment in an artificial vascular network is realized by "opening-closing" of the SMMF mouth. With the continuous optimization of size, motion control, and imaging technology, these magnetic SMMRs will provide ideal platforms for complex microcargo operations and on-demand drug release.

Downregulation of long noncoding RNA SNHG6 rescued propofol-induced cytotoxicity in human induced pluripotent stem cell-derived cardiomyocytes.

BACKGROUND: Propofol (PPF) overdose is a rare but lethal condition, which may lead to severe cardiac failure. In this study, we established an in vitro PPF-induced cardiac cytotoxicity model, and investigate the functional role of long non-coding RNA (lncRNA) small nucleolar RNA host gene 6 (SNHG6). METHODS: Human induced pluripotent stem cell-derived cardiomyocytes (HiPSC-CMs) were exposed to PPF in vitro. PPF-induced cytotoxic effects were measured. PPF-induced SNHG6 expression change in HiPSC-CMs were monitored by qRT-PCR. SNHG6 was downregulated in HiPSC-CMs to examine its role in PPF-induced cardiac cytotoxicity. The expression of competing endogenous RNA (ceRNA) candidate of SNHG6, human microRNA-186-5p (hsa-miR-186-5p) was also investigated in PPF-exposed HiPSC-CMs. Functions of hsa-miR-186-5p were further investigated in PPF-exposed and SNHG6-downregulated HiPSC-CMs. RESULTS: PPF induced significant cytotoxicity, as well as SNHG6 upregulation in HiPSC-CMs. SNHG6 downregulation had rescuing effects on PPF-induced cardiac cytotoxicity. Dual-luciferase activity assay confirmed that hsa-miR-186-5p was the ceRNA candidate of SNHG6. QRT-PCR showed hsa-miR-186-5p expression was reversely correlated with SNHG6 in PPF-exposed HiPSC-CMs. Suppressing hsa-miR-186-5p reduced the rescuing effects of SNHG6-downregulation on PPF-induced cardiac cytotoxicity. CONCLUSIONS: SNHG6/hsa-miR-186-5p can modulate PPF-induced cardiac cytotoxicity in HiPSC-CMs, and thus may be a future drug target to prevent PPF infusion syndrome.