Open Questions of Chemically Powered Nano- and Micromotors

Motion control of chemically powered colloidal motors

Chemically powered colloidal motors can convert chemical energy into directional mechanical movement, making them promising for applications such as targeted drug delivery, environmental decontamination, and precision disease treatment. However, their self-propulsion is constantly disrupted by random Brownian motion, making precise control under low Reynolds number conditions highly challenging. This review provides a brief overview of the three main propulsion mechanisms of chemically powered colloidal motors. It also summarizes recent advances in motion control, including speed regulation and trajectory navigation. Finally, we discuss future directions for achieving more precise motion control. We hope this review will inspire further research on developing more effective and practical control strategies for colloidal motors.

Fast and Autonomous Mannosylated Nanomotors for Dynamic Cancer Cell Targeting

An attractive strategy in cancer cell therapy is to employ motile nanoparticles that can actively search for their target. Herein, we introduce mannosylated compartmentalized cross-linked enzyme-driven nanomotors (c-CLEnM), which exhibit specific and efficient targeting of Hep G2 cells through elevated autonomous motion. In this design, we constructed biodegradable bowl-shaped stomatocytes encapsulating the enzymes glucose oxidase (GOx) and catalase (CAT) within their nanocavity. A subsequent enzyme crosslinking reaction was performed to guarantee their stability. Furthermore, the c-CLEnM were surface modified with a mannose-functional glycopolymer, enabling binding with receptors expressed on Hep G2 cells. Interestingly, the targeting ligands on the nanomotors not only improved their specificity toward cancer cells but also enhanced motility. Compared to the non-mannosylated nanomotors, mannosylated c-CLEnM exhibited enhanced motion and higher targeting efficiency to cells in glucose-containing ionic environments. The unexpected acceleration in speed resulted from the surface modification of these nanomotors with a glycopolymer layer, which increased the zeta potential and created a shielding effect that mitigated the influence of the surrounding ions. This nanomotor design highlights the synergistic effect of functional glycopolymer modification on cellular uptake, adding an additional level of control to nanomotors for application in cancer therapy.

Anti-biopassivated Reticular Micromotors for Bladder Cancer Therapy

The limited lifespan of enzyme-powered micro/nanomotors (MNMs) hinders their biomedical applications due to the easy deactivation in tumor microenvironments. In this study, by taking advantage of hydrogen bond-rich metal-organic frameworks (MOFs), we design anti-biopassivated urease-powered MOF motors (Ur-MOFtors) with sustained motility for bladder cancer therapy. Such reticular Ur-MOFtors exhibited an exceptionally long locomotion lifespan exceeding 90 min in highly concentrated urea, which was an 18-fold enhancement compared with urease-adsorbed MOFs, resulting in excellent anti-biopassivation of MOFtors. The underlying molecular mechanism of persistent motion involves hydrogen bonding interaction between the MOF skeleton and the catalytic product, as identified by in situ infrared spectroscopy and density functional theory. Based on the preserved enzymatic activity comparable to native urease, the self-propulsion pathway of Ur-MOFtors is driven by ionic self-diffusiophoresis with the positive chemotactic motion toward urea. Benefiting from the persistent motion of Ur-MOFtors in physiological urea, a rapid bladder cancer therapy was achieved with few instillation sessions and short treatment cycles during intravesical administration. This hydrogen bond-rich framework presents a promising anti-biopassivated approach to overcoming the short lifespan and easy deactivation of enzymatic motors for advanced therapeutic robotics.

Single-Atom Colloidal Nanorobotics Enhanced Stem Cell Therapy for Corneal Injury Repair

Corneal repair using mesenchymal stem cell therapy faces challenges due to long-term cell survival issues. Here, we design cerium oxide with gold single-atom-based nanorobots (CeSAN-bots) for treating corneal damage in a synergistic combination with stem cells. Powered by glucose, CeSAN-bots exhibit enhanced diffusion and active motion due to the cascade reaction catalyzed by gold and cerium oxide. CeSAN-bots demonstrate a two-fold increase in cellular uptake efficiency into mesenchymal stem cells compared to passive uptake. CeSAN-bots possess intrinsic antioxidant and immunomodulatory properties, promoting corneal regeneration. Validation in a mouse corneal alkali burn model reveals an improvement in corneal clarity restoration when stem cells are incorporated with CeSAN-bots. This work presents a strategy for developing glucose-driven, enzyme-free, single-atom-based ultrasmall nanorobots with promising applications in targeted intracellular delivery in diverse biological environments.

Chemically active colloidal superstructures

Mimicking biological systems, artificial active colloidal motors that continuously dissipate energy can dynamically self-assemble to form active colloidal superstructures with specific spatial configurations and complex functionalities, which offers a promising pathway for developing new active soft matter materials with adaptability, self-repair, and reconfigurability. Beyond merely propelling their own motion, chemically driven colloidal motors can also induce phoretic effects and osmotic flows to affect the motion of neighboring colloidal motors through local fluid fields generated by chemical reactions, thereby achieving spontaneous chemical communication and promoting dynamic self-assembly between motors. This review summarizes the latest progress in the dynamic self-assembly of chemically driven colloidal motors, ranging from single chemically driven colloidal motors to chemically driven colloidal motors with passive colloidal particles and then to different chemically driven colloidal motors, ultimately forming active colloidal superstructures with complex dynamic behaviors. Not only are the interactions between chemically driven colloidal motors with different self-propulsion mechanisms and passive colloidal particles focused on, but also the communication behaviors between chemically driven colloidal motors are explored. We explain the fundamental physicochemical mechanisms that regulate the assembly behavior of chemically driven colloidal motors, propose general strategies for the controlled construction of active colloidal superstructures, and discuss the potential applications that may emerge from the directed dynamic self-assembly of these superstructures.

Liquid Metal Amplified Charge Separation in Photocatalytic Micro/Nanomotors for Antibacterial Therapy

Photocatalytic micro/nanomotors (MNMs) driven by electrophoresis have attracted considerable attention by virtue of their active mobility and versatile functionality. However, the rapid recombination of photogenerated electron-hole pairs on light illumination severely compromises the involvement of charge species in the catalytic redox reactions of fuels, thus hindering both the propulsion and the application performance of photocatalytic MNMs. Herein, we report a facile strategy to amplify charge separation by incorporating liquid metal (LM) into the construction of photocatalytic MNMs, thereby strengthening the electrophoretic propulsion of MNMs and promoting the generation of reactive oxygen species (ROS) for antibacterial application. The MNMs are constructed with a gallium (Ga) LM core, coated with abundant graphite-phase carbon nitride (g-C3N4) nanosheets and half covered by a thin platinum layer. These MNMs exhibit self-propulsion in hydrogen peroxide (H2O2) solution, with their motion dynamics further enhanced by light irradiation. Theoretical calculations and simulations reveal that the composition between Ga and g-C3N4 forms an ohmic junction in the electronic energy band structure, which effectively improves the charge separation efficiency of electron-hole pairs. These results align well with the experimental electrochemical tests and consequently intensify the catalytic redox reactions of H2O2, as well as accelerate the charge migration across MNMs, contributing to the enhancement of their propulsion performance. Simultaneously, the amplified separation of electrons facilitates increased ROS generation, empowering the MNMs with motion-enhanced antibacterial activity against Escherichia coli. Finally, an in vivo wound healing experiment is conducted, verifying the superior antibacterial therapeutic performance of photocatalytic MNMs. This work not only provides insights into the role of charge species in phoretic motion of MNMs but also gives inspiration for developing photocatalytic MNMs with advanced biomedical applications.

Ionic Diffusiophoresis of Active Colloids via Galvanic Exchange Reactions

In order to move toward realistic applications by extending active matter propulsion reactions beyond the classical catalytic hydrogen peroxide decomposition, we investigate the self-propulsion mechanism of Janus particles. To address the influences of ionic species, we investigate Janus particles driven by a galvanic exchange reaction that consumes and produces ions on one hemisphere. Our galvanophoretic experiments in the regime of thin Debye layers confirm that even the simplest models in active matter are still full of important surprises. We find a logarithmic speed dependence on the fuel concentration, which cannot be explained using the classic ionic self-diffusiophoretic framework. Instead, an approach based on the Poisson-Nernst-Planck equations yields a better agreement with the experiments. We attribute the discrepancy between the two models to the breakdown of two key hypotheses of the ionic self-diffusiophoretic approach.

Reconfigurable Transport and Assembly of Colloidal Particles via Opto-Chemical-Electronic Tweezer (OCET)

Transporting and assembling colloidal particles is key to applications such as drug delivery, the fabrication of functional materials, and microrobotics. As a result, there is intense effort in developing techniques for manipulating colloids at high spatial and temporal resolutions, and in a dynamic, reconfigurable manner. Although optical manipulation provides precise particle control, its application is often limited by high energy requirements and intricate setups. In this study, we present an opto-chemical-electronic tweezer (OCET), a novel particle manipulation strategy that addresses these limitations. The OCET system utilizes a photocatalytic TiO2/Pt film irradiated with perpendicular UV light. An electric field is then generated parallel to the film at the boundary of the patterned UV light, directed from the illuminated region to the dark region. The consequent electrophoresis and electroosmosis work in tandem to move inert colloidal particles (e.g., SiO2 microspheres) at ∼1 μm/s and trap them a few μm inside the illuminated region along the boundary of the light pattern. By dynamically modulating light patterns, the OCET system achieves directional particle transport and reconfigurable colloidal assembly into arbitrary patterns. The OCET system holds promise for applications in optofluidics, micro/nanorobotics, and biomedical systems, setting the stage for further advancements in optical manipulation technologies.

Quantifying and understanding the tilt of a Pt Janus active colloid near solid walls

Active colloids powered by self-generated gradients are influenced by nearby solid boundaries, leading to their reorientation. In this study, the tilt angles (the angle between where an active colloid moves and where it faces) were measured to be 13.3° and -33.9° for 5 μm polystyrene microspheres half coated with 10 nm Pt caps moving in 5% H2O2 along the bottom and top glass wall, respectively, indicating that the colloids moved with their PS (forward) caps tilted slightly toward the wall. The speeds and tilt angles of Pt Janus colloids increased consistently with increasing H2O2 concentration (0.5 to 10 v/v%) and Pt cap thickness (5 to 50 nm). We propose that the tilt results from a balance between gravitational torque (caused by the Pt cap's weight) and chemical activity-induced torque (from self-generated chemical gradients), qualitatively supported by finite element simulations based on self-electrophoresis. Our findings are useful for understanding how chemically active colloids move in, and interact with, their environment.

Colloidal ionogels: Controlled assembly and self-propulsion upon tunable swelling

Active colloids driven out of thermal equilibrium serve as building blocks for smart materials with tunable structures and functions. Using chemical energy to drive colloids is advantageous but requires precise control over chemical release. To address this, we developed colloidal ionogels-polymer microspheres infused with ionic liquids-that show controlled assembly and self-propulsion upon tunable swelling. For example, we synthesized microspheres of polymethylmethacrylate loaded with ionic liquid [Bmim][PF6], which were released from the colloidal ionogel upon swelling in alcohol-water mixtures and dissociated into cations and anions of different diffusivities. The resulting electric field leads to four types of pair-wise colloidal interactions via ionic diffusiophoresis and diffusioosmosis, giving rise to four types of self-assembled superstructures. These interactions were precisely modulated by altering the swelling conditions and the ionic liquids used. Additionally, partially blocking the ionogel's surface induces anisotropic swelling and asymmetric ion release, turning the colloidal ionogel into a self-propelled Janus colloidal motor powered by ionic self-diffusiophoresis, reaching speeds of several µm/s and lasting about 100 s. These findings indicate that colloidal ionogels are smart colloidal building blocks with highly tunable pair-wise interactions, self-assembled structures, and self-propulsion, offering potential applications in biomedical sensing, environmental monitoring, and photonics.

Phosphatidylcholine Liposome Accelerated Platinum Nanomachines (PLANEs) With Enhanced Penetration Capability for Thrombus Mechanotherapy

Thrombotic cardiovascular diseases remain the leading cause of mortality worldwide. However, current thrombolytic therapeutics suffer from limited efficacy and a high risk of severe bleeding. Here, a phosphatidylcholine liposome accelerated platinum nanomachine (PLANE) for thrombus mechanotherapy is designed, constructed by encapsulating platinum nanomotors within isotropic, lubricating phosphatidylcholine (PC) liposomes. The precisely engineered PLANE exhibits superior lubricity and linear motion. Under laser irradiation and hydrogen peroxide treatment, PLANEs achieve significantly higher velocities than conventional platinum nanomotors, facilitating deep penetration into the thrombi. Further functionalization with thrombus-targeting peptides enables the cPLANEs to selectively accumulate at the thrombotic sites in vivo, demonstrating excellent thrombolytic efficacy. This work presents a novel surface modification strategy for optimizing the motion behavior of platinum nanomotors, offering a promising non-pharmaceutic approach for thrombotic disease treatment.

From Autonomous Chemical Micro-/Nanomotors to Rationally Engineered Bio-Interfaces

Developing micro-/nanomotors that convert a chemical energy input into a local gradient field and motion is an appealing but challenging task that holds particular promise for the intersection of materials and nanoengineering. Over the past two decades, remarkable advancements have refined these out-of-equilibrium chemically powered micro-/nanomotors, enabling them to orchestrate in situ chemical transformations that dynamically change local environments. The ionic products, radicals, gases, and electric fields from these active materials reshape the microenvironment, paving the way for ecofriendly disease interventions. This review discusses the state-of-the-art reactions that propel these energy-consuming micro-/nanomotors and elucidates the emerging implications of their products on biological systems. Particular emphasis has been placed on their potential for neural modulation, reactive oxygen species (ROS) regulation, synergistic tumor therapy, antibacterial strategies, and tissue regeneration. Collectively, these sketches provide a landscape of therapeutic modalities, heralding a new era of biomedicine. By harnessing the in situ product field of this active matter, we envision a paradigm shift toward active therapies that transcend conventional approaches, promising breakthroughs in disease diagnosis, treatment, and prevention.

Janus micro/nanomotors for enhanced disease treatment through their deep penetration capability

Nanotherapeutic systems have provided an innovative means for the treatment of a wide range of diseases in modern medicine. However, the limited penetration of nanoparticles into focal tissues still greatly hampered their clinical application. With their unique two-sided structure and superior motility, Janus micro/nanomotors are expected to significantly improve the penetration of nanocarriers into organisms, thereby enhancing the therapeutic effects of diseases. This review introduces Janus micro/nanomotors with different morphologies and focuses on their propulsion mechanisms, including chemical field-driven, external physical field-driven, biologically-driven, and hybrid-driven mechanisms. We explore the research progress of Janus micro/nanomotors in various disease treatment areas (including cancer, cardiovascular diseases, neurological diseases, bacterial/fungal infections, and chronic inflammatory diseases) and elucidate the implementation strategies of Janus micro/nanomotors in facilitating disease therapies. Finally, we discuss the biosafety and biocompatibility of Janus micro/nanomotor, while exploring current challenges and opportunities in the field. We look forward to the Janus micro/nanomotor therapeutic platform demonstrating surprising therapeutic effects in the clinical treatment of diseases. STATEMENT OF SIGNIFICANCE: Micro/nanomotors are the highly promising nanotherapeutic systems due to their self-propelled motion capability. Janus micro/nanomotors possess an asymmetric structure with different physical or chemical properties on both sides. The flexibility of this bifunctional surface allows them to hold promise for improving the penetration of nanotherapeutic systems and enhancing therapeutic efficacy for complex diseases. This review focuses on the latest advancements in Janus micro/nanomotors for enhanced disease treatment, including the structural types and driving mechanisms, the enhancement effect to cope with different disease treatments, the biocompatibility and safety, the current challenges and possible solutions. These insights inform the design of deep-penetrating nanotherapeutic systems and the strategies of enhanced disease treatment.

Self-Driven Janus Ga/Mg Micromotors for Reducing Deep Bacterial Infection in the Treatment of Periodontitis

A self-propulsion Janus gallium (Ga)/magnesium (Mg) bimetallic micromotor is designed with favorable biocompatibility and antimicrobial properties as a therapeutic strategy for periodontitis. The Janus Ga/Mg micromotors are fabricated by microcontact printing technique to asymmetrically modify liquid metallic gallium onto magnesium microspheres. Hydrogen bubbles produced by the magnesium-water reaction can provide the driving performance of up to 31.03 µm s-1 (pH 6.8), prompting the micromotor to actively breakthrough the biological barrier of saliva and gingival crevice fluid (GCF) into the bottom of periodontal pockets. In addition, the Janus Ga/Mg micromotors are effectively converted by degradation into the built-in antimicrobial ion Ga(III) to eliminate deep-seated Porphyromonas gingivalis (P.gingivalis), with bactericidal efficiencies of over 99.8%. The developed Janus Ga/Mg micromotors have demonstrated potent antimicrobial and anti-inflammatory activity both in vitro and in vivo studies. Crucially, it reduces alveolar bone resorption, demonstrating the superior efficacy of liquid metal gallium in treating periodontitis. Therefore, Ga/Mg bimetallic micromotors hold great promise to be an innovative and translational drug delivery system to treat periodontitis or other inflammation-related diseases in the near future.

Characterization of Nonequilibrium Interactions of Catalytic Microswimmers Using Phoretically Responsive Nanotracers

Catalytic microswimmers convert the chemical energy from fuel into motion. They sustain chemical gradients and fluid flows that propel them by phoresis. This leads to unconventional behavior and collective dynamics, such as self-organization into complex structures. Characterizing the nonequilibrium interactions of microswimmers is crucial for advancing our understanding of active systems. However, this remains a challenge owing to the importance of fluctuations at the microscale and the difficulty in disentangling the different contributions to the interactions. Here, we show a massive dependence of the nonequilibrium interactions on the shape of catalytic microswimmers. We perform tracking experiments at high throughput to map interactions between nanocolloidal tracers and dimeric microswimmers of various aspect ratios. Our method leverages dual tracers with differing phoretic mobilities to quantitatively disentangle phoretic motion from hydrodynamic advection. This approach is validated through experiments on single chemically active sites and on immobilized catalytic microswimmers. We further investigate the activity-driven interactions of free microswimmers and directly measure their phoretic interactions. When compared to standard models, our findings highlight the important role of osmotic flows for microswimmers near surfaces and reveal an enhanced contribution of hydrodynamic advection relative to phoretic motion as the size of the microswimmer increases. Our study provides robust measurements of the nonequilibrium interactions from catalytic microswimmers and lays the groundwork for a realistic description of active systems.

Run-and-tumble like motion of a camphor-infused Marangoni swimmer

'Run-and-tumble' (RT) motion has been a subject of intense research for several decades. Many organisms, such as bacteria, perform such motion in the presence or absence of local chemical concentration gradients and it is found to be advantageous in search processes. Although there are previous reports involving the successful design of non-living self-propelled particles exhibiting such motion in the presence of external stimuli (chemical/mechanical), RT motion with 'rest' has not yet been observed for autonomous non-living active particles. We have designed a swimmer that performs motion using a combination of 'run', 'tumble', and 'rest' states with stochastic transitions. In the present scenario, it arises solely due to self-generated local surface tension gradients. We quantify the residence time statistics by analyzing the swimmer trajectories from the experimental data, which suggests that the 'rest' and 'tumble' states are more frequent than 'run'. Then, we quantify the motion properties by computing the mean squared displacement, which shows that the swimmer performs ballistic motion on a short time scale and then slows down due to tumbling and resting. To validate the observed transport properties, we introduce a minimal model of a chiral active Brownian particle, stochastically switching between three internal states. The model parameters were extracted from the experiments, which rendered a good agreement between the experiments and simulations.

Nano-/Microrobots for Environmental Remediation in the Eyes of Nanoarchitectonics: Toward Engineering on a Single-Atomic Scale

Nano-/microrobots have been demonstrated as an efficient solution for environmental remediation. Their strength lies in their propulsion abilities that allow active "on-the-fly" operation, such as pollutant detection, capture, transport, degradation, and disruption. Another advantage is their versatility, which allows the engineering of highly functional solutions for a specific application. However, the latter advantage can bring complexity to applications; versatility in dimensionality, morphology, materials, surface decorations, and other modifications has a crucial effect on the resulting propulsion abilities, compatibility with the environment, and overall functionality. Synergy between morphology, materials, and surface decorations and its projection to the overall functionality is the object of nanoarchitectonics. Here, we scrutinize the engineering of nano-/microrobots with the eyes of nanoarchitectonics: we list general concepts that help to assess the synergy and limitations of individual procedures in the fabrication processes and their projection to the operation at the macroscale. The nanoarchitectonics of nano-/microrobots is approached from microscopic level, focusing on the dimensionality and morphology, through the nanoscopic level, evaluating the influence of the decoration with nanoparticles and quantum dots, and moving to the decorations on molecular and single-atomic level to allow very fine tuning of the resulting functionality. The presented review aims to lay general concepts and provide an overview of the engineering of functional advanced nano-/microrobot for environmental remediation procedures and beyond.

Shape-Directed Dynamic Assembly of Active Colloidal Metamachines

Modularly organizing active micromachines into high-grade metamachines makes a great leap for operating the microscopic world in a biomimetic way. However, modulating the nonreciprocal interactions among different colloidal motors through chemical reactions to achieve the controllable construction of active colloidal metamachines with specific dynamic properties remains challenging. Here, we report the phototactic active colloidal metamachines constructed by shape-directed dynamic self-assembly of chemically driven peanut-shaped TiO2 colloidal motors and Janus spherical Pt/SiO2 colloidal motors. The long-range diffusiophoretic attraction generated by the photocatalytic reaction dominates the sensing and collision of peanut TiO2 motors with Janus Pt/SiO2 motors. The coupling of local chemical concentration gradient fields between the two types of motors generates short-range site-selective interactions, promoting the shape-directed assembly toward active colloidal metamachines with well-defined spatial configurations. Metamachines, made of colloidal motors, exhibit configuration-dependent kinematics. The colloidal metamachines can be reversibly reconstructed by adjusting lighting conditions and can move phototactically along a predetermined path under the structured light field. Such chemically driven colloidal metamachines that integrate multiple active agents provide a significant avenue for fabricating active soft matter materials and intelligent robotic systems with advanced applications.

Single molecule-driven nanomotors reveal the dynamic-disordered chemomechanical transduction of active enzymes

Enzymes facilitate the conversion of chemical energy into mechanical work during biochemical reactions, thereby regulating the dynamic metabolic activity of living systems. However, directly observing the energy release facilitated by fluctuating individual enzymes remains a challenge, leading to a contentious debate regarding the underlying reasons for this phenomenon. Here, we aim to overcome this challenge by developing an oscillating nanomotor powered by a single-molecule enzyme, which allows real-time tracking of energy transduction in enzymatic reactions. Through analysis of the shifts in free energy profiles within the nanomotors, our results unveil not only the heterogeneous energy release patterns of individual enzyme molecules but also the dynamic disorder of a particular enzyme in energy release over extended monitoring periods. By exploring six distinct types of single-molecule enzymatic reactions, we provide the direct evidence supporting the argument that the reaction enthalpy governs the enzymatic energy release. This approach has implications for understanding the mechanism of enzymatic catalysis and developing highly efficient nanomotors.

Self-organization of Janus particles: Impact of hydrodynamic interactions in substrate consumption for structure formation

We show that the formation of active matter structures requires them to modify their surroundings by creating inhomogeneities such as concentration gradients and fluid flow around the structure constituents. This modification is crucial for the stability of the ordered structures. We examine the formation of catalytic Janus particle aggregates at low volumetric fractions in the presence of hydrodynamic interactions (HIs). Our study shows the types of structures formed for various values of the kinetic constant of the catalytic reaction. The presence of HI causes the aggregate particles to have higher mobility than in the case of the absence of such interactions, which is reflected in the behavior of the pair distribution function. Although HI decreases energy conversion efficiency, they play a significant role in the formation of complex structures found in nature. Self-organization of these structures is driven by direct feedback loops between structure formation and the surrounding medium. As the structures alter the medium by consuming substrate and perturbing fluid flow, the substrate concentration, in turn, dictates the kinetics and configuration of the structures.

Ion-exchange induced multiple effects to promote uranium uptake from nonmarine water by micromotors

As the fundamental resource in nuclear energy, uranium is a sword of two sides, due to its radioactive character that could cause severe impact to the environment and living creatures once released by accident. However, limited by the passive ion transport, the currently available uranium adsorbents still suffer from low adsorption kinetics and capacity. Here, we report a self-driven modular micro-reactor composed of magnetizable ion-exchange resin and adsorbents that can be used to dynamically remove uranium from nonmarine waters. Because of the long-range pH gradient and phoretic flow established by the recyclable ion-exchange resin, the micro-reactor shows a fast uranium adsorption rate and reaches a uranium extraction capacity of 629.3 mg g-1 within 10 min in 30 ppm uranium solution, as well as good recyclability in repeated use. Numerical simulation result confirms that the phoretic flow and electric field accelerate uranium transport to the adsorbent. Our work provides a new solution for the removal of radioactive uranium with high efficiency.

Temperature-Sensitive Polymer-Driven Nanomotors for Enhanced Tumor Penetration and Photothermal Therapy

Self-propelled nanomotors possess strong propulsion and penetration abilities, which can increase the efficiency of cellular uptake of nanoparticles and enhance their cytotoxicity against tumor cells, opening a new path for treating major diseases. In this study, the concept of driving nanomotors by alternately stretching and contracting a temperature-sensitive polymer (TS-P) chain is proposed. The TS-Ps are successfully linked to one side of Cu2-xSe@Au (CS@Au) nanoparticles to form a Janus structure, which is designated as Cu2-xSe@Au-polymer (CS@Au-P) nanomotors. Under near-infrared (NIR) light irradiation, Cu2-xSe nanoparticles generate photothermal effects that change the system temperature, triggering the alternation of the TS-P structure to generate a mechanical force that propels the motion of CS@Au-P nanomotors. The nanomotor significantly improved the cellular uptake of nanoparticles and enhanced their penetration and accumulation in tumor. Furthermore, the exceptional photothermal conversion efficiency of CS@Au-P nanomotors suggests their potential as nanomaterials for photothermal therapy (PTT). The prepared material exhibited good biocompatibility and anti-tumor effects both in vivo and in vitro, providing new research insights into the design and application of nanomotors in tumor therapy.

Recent advances in the development of tumor microenvironment-activatable nanomotors for deep tumor penetration

Cancer represents a significant threat to human health, with the use of traditional chemotherapy drugs being limited by their harsh side effects. Tumor-targeted nanocarriers have emerged as a promising solution to this problem, as they can deliver drugs directly to the tumor site, improving drug effectiveness and reducing adverse effects. However, the efficacy of most nanomedicines is hindered by poor penetration into solid tumors. Nanomotors, capable of converting various forms of energy into mechanical energy for self-propelled movement, offer a potential solution for enhancing drug delivery to deep tumor regions. External force-driven nanomotors, such as those powered by magnetic fields or ultrasound, provide precise control but often necessitate bulky and costly external equipment. Bio-driven nanomotors, propelled by sperm, macrophages, or bacteria, utilize biological molecules for self-propulsion and are well-suited to the physiological environment. However, they are constrained by limited lifespan, inadequate speed, and potential immune responses. To address these issues, nanomotors have been engineered to propel themselves forward by catalyzing intrinsic "fuel" in the tumor microenvironment. This mechanism facilitates their penetration through biological barriers, allowing them to reach deep tumor regions for targeted drug delivery. In this regard, this article provides a review of tumor microenvironment-activatable nanomotors (fueled by hydrogen peroxide, urea, arginine), and discusses their prospects and challenges in clinical translation, aiming to offer new insights for safe, efficient, and precise treatment in cancer therapy.

Controlled Surface Textures of Elastomeric Polyurethane Janus Particles: A Comprehensive Review

Colloidal particle research has witnessed significant advancements in the past century, resulting in a plethora of studies, novel applications, and beneficial products. This review article presents a cost-effective and low-tech method for producing Janus elastomeric particles of varied geometries, including planar films, spherical particles, and cylindrical fibers, utilizing a single elastomeric material and easily accessible chemicals. Different surface textures are attained through strain application or solvent-induced swelling, featuring well-defined wavelengths ranging from sub-microns to millimeters and offering easy adjustability. Such versatility renders these particles potentially invaluable for medical applications, especially in bacterial adhesion studies. The coexistence of "young" regions (smooth, with a small surface area) and "old" regions (wrinkled, with a large surface area) within the same material opens up avenues for biomimetic materials endowed with additional functionalities; for example, a Janus micromanipulator where micro- or nano-sized objects are grasped and transported by an array of wrinkled particles, facilitating precise release at designated locations through wrinkle pattern adjustments. This article underscores the versatility and potential applications of Janus elastomeric particles while highlighting the intriguing prospects of biomimetic materials with controlled surface textures.

Exploring the Synthesis of Self-Organization and Active Motion

Proteins, genetic material, and membranes are fundamental to all known organisms, yet these components alone do not constitute life. Life emerges from the dynamic processes of self-organization, assembly, and active motion, suggesting the existence of similar artificial systems. Against this backdrop, our Perspective explores a variety of chemical phenomena illustrating how nonequilibrium self-organization and micromotors contribute to life-like behavior and functionalities. After explaining key terms, we discuss specific examples including enzymatic motion, diffusiophoretic and bubble-driven self-propulsion, pattern-forming reaction-diffusion systems, self-assembling inorganic aggregates, and hierarchically emergent phenomena. We also provide a roadmap for combining self-organization and active motion and discuss possible outcomes through biological analogs. We suggest that this research direction, deeply rooted in physical chemistry, offers opportunities for further development with broad impacts on related sciences and technologies.

Reconfigurable Assembly of Planar Colloidal Molecules via Chemical Reaction and Electric Polarization

Colloidal molecules, ordered structures assembled from micro- and nanoparticles, serve as a valuable model for understanding the behavior of real molecules and for constructing materials with tunable properties. In this work, we introduce a universal strategy for assembling colloidal molecules consisting of a central active particle surrounded by several passive particles as ligands. During the assembly process, active particles attract the surrounding passive particles through phoresis and osmosis resulting from the chemical reactions on the surface of the active particles, while passive particles repel each other due to the electric polarization induced by an alternating current (AC) electric field. By carefully selecting particles of varying structures and sizes, we have assembled colloidal molecules of symmetric and asymmetric dimers, trimers, and multimers. Furthermore, the coordination number of these colloidal molecules can be regulated in real time and in situ by tuning the interaction forces between the constituent particles. Brownian dynamics simulations reproduced the formation of the colloidal molecules and validated that the self-assembly arises from chemically induced attraction and electrical dipolar repulsion. This strategy for reconfigurable colloidal assemblies poses the potential for designing adaptive micro-nanomachines.