Template-Guided Silicon Micromotor Assembly for Enhanced Cell Manipulation.

Light-driven micro/nanorobots (LMNRs) are tiny, untethered machines with great potential in fields like precision medicine, nano manufacturing, and various other domains. However, their practicality hinges on developing light-manipulation strategies that combine versatile functionalities, flexible design options, and precise controllability. Our study introduces an innovative approach to construct micro/nanorobots (MNRs) by utilizing micro/nanomotors as fundamental building blocks. Inspired by silicon Metal-Insulator-Semiconductor (MIS) solar cell principles, we design a new type of optomagnetic hybrid micromotors (OHMs). These OHMs have been skillfully optimized with integrated magnetic constituent, resulting in efficient light propulsion, precise magnetic navigation, and the potential for controlled assembly. One of the key features of the OHMs is their ability to exhibit diverse motion modes influenced by fracture surfaces and interactions with the environment, streamlining cargo conveyance along "micro expressway"-the predesigned microchannels. Further enhancing their versatility, a template-guided assembly strategy facilitates the assembly of these micromotors into functional microrobots, encompassing various configurations such as "V-shaped", "N-shaped", and 3D structured microrobots. The heightened capabilities of these microrobots, underscore the innovative potential inherent in hybrid micromotor design and assembly, which provides a foundational platform for the realization of multi-component microrobots. Our work moves a step toward forthcoming microrobotic entities boasting advanced functionalities.

Super-Assembled Multilayered Mesoporous TiO2 Nanorockets for Light-Powered Space-Confined Microfluidic Catalysis.

In the field of sustainable chemistry, it is still a significant challenge to realize efficient light-powered space-confined catalysis and propulsion due to the limited solar absorption efficiency and the low mass and heat transfer efficiency. Here, novel semiconductor TiO2 nanorockets with asymmetric, hollow, mesoporous, and double-layer structures are successfully constructed through a facile interfacial superassembly strategy. The high concentration of defects and unique topological features improve light scattering and reduce the distance for charge migration and directed charge separation, resulting in enhanced light harvesting in the confined nanospace and resulting in enhanced catalysis and self-propulsion. The movement velocity of double-layered nanorockets can reach up to 10.5 µm s-1 under visible light, which is approximately 57 and 119% higher than that of asymmetric single-layered TiO2 and isotropic hollow TiO2 nanospheres, respectively. In addition, the double-layered nanorockets improve the degradation rate of the common pollutant methylene blue under sustainable visible light with a 247% rise of first-order rate constant compared to isotropic hollow TiO2 nanospheres. Furthermore, FEA simulations reveal and confirm the double-layered confined-space enhanced catalysis and self-propulsion mechanism.

Triple Hybrid Cellular Nanovesicles Promote Cardiac Repair after Ischemic Reperfusion.

The management of myocardial ischemia/reperfusion (I/R) damage in the context of reperfusion treatment remains a significant hurdle in the field of cardiovascular disorders. The injured lesions exhibit distinctive features, including abnormal accumulation of necrotic cells and subsequent inflammatory response, which further exacerbates the impairment of cardiac function. Here, we report genetically engineered hybrid nanovesicles (hNVs), which contain cell-derived nanovesicles overexpressing high-affinity SIRPα variants (SαV-NVs), exosomes (EXOs) derived from human mesenchymal stem cells (MSCs), and platelet-derived nanovesicles (PLT-NVs), to facilitate the necrotic cell clearance and inhibit the inflammatory responses. Mechanistically, the presence of SαV-NVs suppresses the CD47-SIRPα interaction, leading to the promotion of the macrophage phagocytosis of dead cells, while the component of EXOs aids in alleviating inflammatory responses. Moreover, the PLT-NVs endow hNVs with the capacity to evade immune surveillance and selectively target the infarcted area. In I/R mouse models, coadministration of SαV-NVs and EXOs showed a notable synergistic effect, leading to a significant enhancement in the left ventricular ejection fraction (LVEF) on day 21. These findings highlight that the hNVs possess the ability to alleviate myocardial inflammation, minimize infarct size, and improve cardiac function in I/R models, offering a simple, safe, and robust strategy in boosting cardiac repair after I/R.

Colloidal Self-Assembly: From Passive to Active Systems.

Self-assembly fundamentally implies the organization of small sub-units into large structures or patterns without the intervention of specific local interactions. This process is commonly observed in nature, occurring at various scales ranging from atomic/molecular assembly to the formation of complex biological structures. Colloidal particles may serve as micrometer-scale surrogates for studying assembly, particularly for the poorly understood kinetic and dynamic processes at the atomic scale. Recent advances in colloidal self-assembly have enabled the programmable creation of novel materials with tailored properties. We here provide an overview and comparison of both passive and active colloidal self-assembly, with a discussion on the energy landscape and interactions governing both types. In the realm of passive colloidal assembly, many impressive and important structures have been realized, including colloidal molecules, one-dimensional chains, two-dimensional lattices, and three-dimensional crystals. In contrast, active colloidal self-assembly, driven by optical, electric, chemical, or other fields, involves more intricate dynamic processes, offering more flexibility and potential new applications. A comparative analysis underscores the critical distinctions between passive and active colloidal assemblies, highlighting the unique collective behaviors emerging in active systems. These behaviors encompass collective motion, motility-induced phase segregation, and exotic properties arising from out-of-equilibrium thermodynamics. Through this comparison, we aim to identify the future opportunities in active assembly research, which may suggest new application domains.

Magnetically Manipulated Optoelectronic Hybrid Microrobots for Optically Targeted Non-Genetic Neuromodulation.

Optically controlled neuromodulation is a promising approach for basic research of neural circuits and the clinical treatment of neurological diseases. However, developing a non-invasive and well-controllable system to deliver accurate and effective neural stimulation is challenging. Micro/nanorobots have shown great potential in various biomedical applications because of their precise controllability. Here, a magnetically-manipulated optoelectronic hybrid microrobot (MOHR) is presented for optically targeted non-genetic neuromodulation. By integrating the magnetic component into the metal-insulator-semiconductor junction design, the MOHR has excellent magnetic controllability and optoelectronic properties. The MOHR displays a variety of magnetic manipulation modes that enables precise and efficient navigation in different biofluids. Furthermore, the MOHR could achieve precision neuromodulation at the single-cell level because of its accurate targeting ability. This neuromodulation is achieved by the MOHR's photoelectric response to visible light irradiation, which enhances the excitability of the targeted cells. Finally, it is shown that the well-controllable MOHRs effectively restore neuronal activity in neurons damaged by ß-amyloid, a pathogenic agent of Alzheimer's disease. By coupling precise controllability with efficient optoelectronic properties, the hybrid microrobot system is a promising strategy for targeted on-demand optical neuromodulation.

Tunable Self-Thermophoretic Nanomotors with Polymeric Coating.

Thermophoretic micro/nanomotors (MNMs) generate self-propulsion without a chemical reaction. Intrinsically, this promises excellent biocompatibility and is thus suitable for biomedical applications. However, their propulsion efficiency is severely limited due to the poor understanding of the thermophoretic process, which dominates the conversion from thermal energy into mechanical movement. We here developed a series of self-thermophoresis light-powered MNMs with variable surface coatings and discovered obvious self-thermophoresis propulsion enhancement of the polymeric layer. An intrinsically negative self-thermophoretic movement is also observed for the first time in the MNM system. We propose that enthalpic contributions from polymer-solvent interactions should play a fundamental role in the self-thermophoretic MNMs. Quantitative microcalorimetry and molecular dynamics simulations are performed to support our hypothesis. The polymer solvation enthalpy and coating thickness influences on self-thermophoresis are investigated, further highlighting the essential enthalpy contributions to thermophoresis. Our work indicates that surface grafting would be important in designing high-efficiency thermally driven nanorobotic systems for biomedical applications.

Photochromism from wavelength-selective colloidal phase segregation.

Phase segregation is ubiquitously observed in immiscible mixtures, such as oil and water, in which the mixing entropy is overcome by the segregation enthalpy1-3. In monodispersed colloidal systems, however, the colloidal-colloidal interactions are usually non-specific and short-ranged, which leads to negligible segregation enthalpy4. The recently developed photoactive colloidal particles show long-range phoretic interactions, which can be readily tuned with incident light, suggesting an ideal model for studying phase behaviour and structure evolution kinetics5,6. In this work, we design a simple spectral selective active colloidal system, in which TiO2 colloidal species were coded with spectral distinctive dyes to form a photochromic colloidal swarm. In this system, the particle-particle interactions can be programmed by combining incident light with various wavelengths and intensities to enable controllable colloidal gelation and segregation. Furthermore, by mixing the cyan, magenta and yellow colloids, a dynamic photochromic colloidal swarm is formulated. On illumination of coloured light, the colloidal swarm adapts the appearance of incident light due to layered phase segregation, presenting a facile approach towards coloured electronic paper and self-powered optical camouflage.

Activity-assisted barrier crossing of self-propelled colloids over parallel microgrooves.

We report a systematic study of the dynamics of self-propelled particles (SPPs) over a one-dimensional periodic potential landscape U_{0}(x), which is fabricated on a microgroove-patterned polydimethylsiloxane (PDMS) substrate. From the measured nonequilibrium probability density function P(x;F_{0}) of the SPPs, we find that the escape dynamics of the slow rotating SPPs across the potential landscape can be described by an effective potential U_{eff}(x;F_{0}), once the self-propulsion force F_{0} is included into the potential under the fixed angle approximation. This work demonstrates that the parallel microgrooves provide a versatile platform for a quantitative understanding of the interplay among the self-propulsion force F_{0}, spatial confinement by U_{0}(x), and thermal noise, as well as its effects on activity-assisted escape dynamics and transport of the SPPs.

Self-driven magnetorobots for recyclable and scalable micro/nanoplastic removal from nonmarine waters.

Micro/nanoplastic (MNP) contamination in nonmarine waters has evolved into a notable ecotoxicological threat to the global ecosystem. However, existing strategies for MNP removal are typically limited to chemical flocculation or physical filtering that often fails to decontaminate plastic particulates with ultrasmall sizes or ultralow concentrations. Here, we report a self-driven magnetorobot comprising magnetizable ion-exchange resin sphere that can be used to dynamically remove or separate MNPs from nonmarine waters. As a result of the long-range electrophoretic attraction established by recyclable ion-exchange resin, the magnetorobot shows sustainable removal efficiency of >90% over 100 treatment cycles, with verified broad applicability to varying plastic compositions, sizes, and shapes as well as nonmarine water samples. Our work may facilitate industry-scale MNP removal with affordable cost and minimal secondary pollution and suggests an appealing strategy based on self-propelled micro/nanorobots to sample and assess nanoplastics in aqueous environment.

A decoy microrobot that removes SARS-CoV-2 and its variants in wastewater.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which can persist in wastewater for several days, has a risk of waterborne-human transmission. The emergence of SARS-CoV-2 variants with increased infection capacity further highlights the need to remove the virus and restrict its spread in wastewater. Here, we report a decoy microrobot created by camouflaging algae with cell membranes displaying angiotensin-converting enzyme 2 (ACE2) for effective elimination of SARS-CoV-2 and its variants. The decoy microrobots show fast self-propulsion (>85 µm/s), allowing for successful "on-the-fly" elimination of SARS-CoV-2 spike proteins and pseudovirus in wastewater. Moreover, relying on the robust binding between ACE2 and SARS-CoV-2 variants, the decoy microrobots exhibit a broad-spectrum elimination of virus with a high efficiency of 95% for the wild-type strain, 92% for the Delta variant, and 93% for the Omicron variant, respectively. Our work presents a simple and safe decoy microrobot aimed toward eliminating viruses and other environmental hazards from wastewater.

Light-responsive self-strained organic semiconductor for large flexible OFET sensing array.

With the wide application of organic semiconductors (OSCs), researchers are now grappling with a new challenge: design and synthesize OSCs materials with specific functions to satisfy the requirements of high-performance semiconductor devices. Strain engineering is an effective method to improve the semiconductor material's carrier mobility, which is fundamentally originated from the rearrangement of the atomic packing model of materials under mechanic stress. Here, we design and synthesize a new OSC material named AZO-BTBT-8 based on high-mobility benzo[b]benzo[4,5]thieno[2,3-d]thiophene (BTBT) as the semiconductor backbone. Octane is employed to increase molecular flexibility and solubility, and azobenzene at the other end of the BTBT backbone provides photoisomerization properties and structural balance. Notably, the AZO-BTBT-8 photoisomerization leads to lattice strain in thin-film devices, where exceptional device performance enhancement is realized. On this basis, a large-scale flexible organic field-effect transistor (OFET) device array is fabricated and realizes high-resolution UV imaging with reversible light response.

Binary Phases and Crystals Assembled from Active and Passive Colloids.

Classic binary materials, ranging from polymer blends to table salts, contain equilibrium phases or crystals of two interacting components. Here, we report on the construction of binary colloidal materials out of equilibrium by employing active particles and passive particles that dynamically interact and organize. Key to our scheme is the introduction of photoactive microspheres whose activity can be precisely tuned. This allows us to leverage the complex nonequilibrium interplay between the constituent components for dynamic coassembly. A wide variety of binary structures have thus been realized, including the liquid-crystal phases and crystal-crystal phases via phase separation and, counterintuitively, the binary crystalline compounds. The obtained structures are validated by computer simulations, which reveal unexpected kinetic pathways that are unique for active systems. With these findings, our strategy could facilitate the design and fabrication of multicomponent materials beyond equilibrium.

Kinetics-Controlled Super-Assembly of Asymmetric Porous and Hollow Carbon Nanoparticles as Light-Sensitive Smart Nanovehicles.

The rational design and controllable synthesis of hollow nanoparticles with both a mesoporous shell and an asymmetric architecture are crucially desired yet still significant challenges. In this work, a kinetics-controlled interfacial super-assembly strategy is developed, which is capable of preparing asymmetric porous and hollow carbon (APHC) nanoparticles through the precise regulation of polymerization and assembly rates of two kinds of precursors. In this method, Janus resin and silica hybrid (RSH) nanoparticles are first fabricated through the kinetics-controlled competitive nucleation and assembly of two precursors. Specifically, silica nanoparticles are initially formed, and the resin nanoparticles are subsequently formed on one side of the silica nanoparticles, followed by the co-assembly of silica and resin on the other side of the silica nanoparticles. The APHC nanoparticles are finally obtained via high-temperature carbonization of RSH nanoparticles and elimination of silica. The erratic asymmetrical, hierarchical porous and hollow structure and excellent photothermal performance under 980 nm near-infrared (NIR) light endow the APHC nanoparticles with the ability to serve as fuel-free nanomotors with NIR-light-driven propulsion. Upon illumination by NIR light, the photothermal effect of the APHC shell causes both self-thermophoresis and jet driving forces, which propel the APHC nanomotor. Furthermore, with the assistance of phase change materials, such APHC nanoparticles can be employed as smart vehicles that can achieve on-demand release of drugs with a 980 nm NIR laser. As a proof of concept, we apply this APHC-based therapeutic system in cancer treatment, which shows improved anticancer performance due to the synergy of photothermal therapy and chemotherapy. In brief, this kinetics-controlled approach may put forward new insight into the design and synthesis of functional materials with unique structures, properties, and applications by adjusting the assembly rates of multiple precursors in a reaction system.

Kinetics-Regulated Interfacial Selective Superassembly of Asymmetric Smart Nanovehicles with Tailored Topological Hollow Architectures.

Hollow nanoparticles featuring tunable structures with spatial and chemical specificity are of fundamental interest. However, it remains a significant challenge to design and synthesize asymmetric nanoparticles with controllable topological hollow architecture. Here, a versatile kinetics-regulated cooperative polymerization induced interfacial selective superassembly strategy is demonstrated to construct a series of asymmetric hollow porous composites (AHPCs) with tunable diameters, architectures and components. The size and number of patches on Janus nanoparticles can be precisely manipulated by the precursor and catalyst content. Notably, AHPCs exhibit excellent photothermal conversion performance under the irradiation of a near infrared (NIR) laser. Thus, AHPCs are utilized as NIR light-triggered nanovehicles and cargos can be controllably released. In brief, this versatile superassembly approach offers a streamlined and powerful toolset to design diverse asymmetric hollow porous composites.

Interfacial Super-Assembly of Ordered Mesoporous Carbon-Silica/AAO Hybrid Membrane with Enhanced Permselectivity for Temperature- and pH-Sensitive Smart Ion Transport.

Nanofluidic devices have been widely used for diode-like ion transport and salinity gradients energy conversion. Emerging reverse electrodialysis (RED) nanofluidic systems based on nanochannel membrane display great superiority in salinity gradient energy harvesting. However, the imbalance between permeability and selectivity limits their practical application. Here, a new mesoporous carbon-silica/anodized aluminum (MCS/AAO) nanofluidic device with enhanced permselectivity for temperature- and pH-regulated energy generation was obtained by interfacial super-assembly method. A maximum power density of 5.04 W m-2 is achieved, and a higher performance can be obtained by regulating temperature and pH. Theoretical calculations are further implemented to reveal the mechanism for ion rectification, ion selectivity and energy conversion. Results show that the MCS/AAO hybrid membrane has great superiority in diode-like ion transport, temperature- and pH-regulated salinity gradient energy conversion.

An AIE-Active Ultrathin Polymeric Self-Assembled Monolayer Sensor for Trace Volatile Explosive Detection.

This work has prepared polymeric self-assembled monolayer (SAM) sensors for the detection of trace volatile nitroaromatic compound (NAC) explosives by fluorescence quenching. A typical aggregation-induced emission (AIE) luminogen 1,1,2,2-tetraphenylethene (TPE) polymerizes into PTPE to increase the fluorescence intensity in the SAMs, and the phosphoric acid acts as the anchor group to form stable covalent bonds with the Al2 O3 substrate. This design takes advantage of the high sensitivity and good stability of SAMs, and high fluorescence intensity, and "wire effect" of the conjugated polymers. The polymeric SAM sensors are prepared on the Al2 O3 silicon wafer and testing paper. Both of them show good response speed, reversibility, selectivity, and sensitivity. The detection limits down to 0.07, 0.35, and 4.11 ppm for TNT, DNB, and NB, respectively, are achieved on the inorganic testing paper. Furthermore, due to the higher fluorescence intensity by interlacing and overlapping of fibers, the detection of the paper can be distinguished by naked eyes even with a low-power handheld UV lamp, which provides an experimental basis for the development of cheap and easy trace NAC explosive sensors.

Active, Yet Little Mobility: Asymmetric Decomposition of H2O2 Is Not Sufficient in Propelling Catalytic Micromotors.

A popular principle in designing chemical micromachines is to take advantage of asymmetric chemical reactions such as the catalytic decomposition of H2O2. Contrary to intuition, we use Janus micromotors half-coated with platinum (Pt) or catalase as an example to show that this ingredient is not sufficient in powering a micromotor into self-propulsion. In particular, by annealing a thin Pt film on a SiO2 microsphere, the resulting microsphere half-decorated with discrete Pt nanoparticles swims ∼80% more slowly than its unannealed counterpart in H2O2, even though they both catalytically produce comparable amounts of oxygen. Similarly, SiO2 microspheres half-functionalized with the enzyme catalase show negligible self-propulsion despite high catalytic activity toward decomposing H2O2. In addition to highlighting how surface morphology of a catalytic cap enables/disables a chemical micromotor, this study offers a refreshed perspective in understanding how chemistry powers nano- and microscopic objects (or not): our results are consistent with a self-electrophoresis mechanism that emphasizes the electrochemical decomposition of H2O2 over nonelectrochemical pathways. More broadly, our finding is a critical piece of the puzzle in understanding and designing nano- and micromachines, in developing capable model systems of active colloids, and in relating enzymes to active matter.

Ligand-Mediated Spatially Controllable Superassembly of Asymmetric Hollow Nanotadpoles with Fine-Tunable Cavity as Smart H2O2-Sensitive Nanoswimmers.

Ligand-mediated interface control has been broadly applied as a powerful tool in constructing sophisticated nanocomposites. However, the resultant morphologies are usually limited to solid structures. Now, a facile spatially controllable ligand-mediated superassembly strategy is explored to construct monodispersed, asymmetric, hollow, open Au-silica (SiO2) nanotadpoles (AHOASTs). By manipulating the spatial density of ligands, the degree of diffusion of silica can be precisely modulated; thus the diameters of the cavity can be continuously tuned. Due to their highly anisotropic, hollow, open morphologies, we construct a multicompartment nanocontainer with enzymes held and isolated inside the cavity. Furthermore, the resulting enzyme-AHOASTs are used as biocompatible smart H2O2-sensitive nanoswimmers and demonstrate a higher diffusion coefficient than other nanoscaled swimmers. We believe that this strategy is critical not only in designing sophisticated hollow nanosystem but also in providing great opportunities for applications in nanomaterial assembly, catalysis, sensors, and nanoreactors.

A Formaldehyde Sensor Based on Self-Assembled Monolayers of Oxidized Thiophene Derivatives.

High-performance formaldehyde sensors play an important role in air quality assessment. Herein, a self-assembled monolayer (SAM) sensor for trace formaldehyde (FA) is fabricated based on the fluorescence enhancement of oxidized thiophene derivatives. In the primary SAM molecules, the functional backbone trithiophene (3T) links to the anchor through an n-propyl group. The anchor with an active Si-Cl bond can form a covalent bond with the SiO2 substrate by solution incubation, which ensures good stability against organic solvents and high sensitivity via monolayer structures. With the alkyl chain's leading, a dense 3T SAM can be obtained on SiO2. Upon exposure to UV light in the presence of oxygen, 3T can be oxidized into a nonfluorescent but coordination-active product with abundant carbonyl groups, which can be doped with FA and induce a blueshifted fluorescence. With this mechanism, we proposed an SAM-based FA sensor by detecting the enhancement of the blueshifted fluorescence. Reliable reversibility, selectivity, stability, and detection limit lower than 1 ppm are achieved in this system. The work provides an experimental basis for developing a cheap, efficient, and flexible sensor for trace FA detection.

Design of an AIE-Active Flexible Self-Assembled Monolayer Probe for Trace Nitroaromatic Compound Explosive Detection.

In this work, a series of molecules TPE-PA-n (n = 3-11) were designed with classic aggregation-induced emission (AIE) 1,1,2,2-tetraphenylethene (TPE) for self-assembled monolayers (SAMs), which are applied for the detection of trace nitroaromatic compound (NAC) explosives. Phosphoric acid that acts as an anchor is used to connect with TPE through alkyl chains of various lengths. It is found that the alkyl chains play a role in pulling TPE luminogens to aggregate for light emission, which can affect the fluorescence and sensing performance of the SAMs. Ulteriorly, a model is built to explore the influence of the alkyl chain length on the device performance, which is determined by the three effects of the alkyl chain: flexibility, the coupling effect, and the odd-even effect. By comparison, the functional molecules with the chain length of 8 were finally selected and further applied for NAC sensors. By means of fluorescence spectra, the SAM sensor was proved to have good stability, reversibility, selectivity, and sensitivity, and its detection limits for trinitrotoluene, dinitrotoluene, and nitrobenzene were 1.2, 6.0, and 35.7 ppm, respectively. This work provides new ideas for the design and preparation of flexible sensors for trace NAC detection with high performance, low cost, and easy operation.