Pick up and dispose of pollutants from water via temperature-responsive micellar copolymers on magnetite nanorobots

Milliscale Shape-Programmable Magnetic Machines Based on Modular Janus Disks

Through billions of years of evolution, small and microorganisms have come to possess distinctive shape-morphing abilities to live in complex fluid environments. However, fabricating milliscale programmable machines with shape-morphing ability often involves complicated architectures requiring arduous fabrication processes and multiple external stimuli. Here, milliscale programmable machines with reconfigurable structures and extensible sizes are proposed based on the sequential assembly of simple Janus disks at liquid surfaces. The modular machines consist of magnetic Janus disks that are assembled into expected chain shapes in turn. Based on the modular structures with programmable shapes, multiple locomotion modes are developed according to their structural characteristics. Their multifunctionality in manipulating and delivering objects through contacting or noncontacting ways based on the programmable structures is demonstrated. The shape-programmable behaviors of the machines open up a new way toward constructing reconfigurable soft microrobots and understanding complex assembly mechanisms.

Sol-gel transition effect based on konjac glucomannan thermosensitive hydrogel for photo-assisted uranium extraction

Exploiting the intelligent photocatalysts capable of phase separation provides a promising solution to the removal of uranium, which is expected to solve the difficulty in separation and the poor selectivity of traditional photocatalysts in carbonate-containing uranium wastewater. In this paper, the γ-FeOOH/konjac glucomannan grafted with phenolic hydroxyl groups/poly-N-isopropylacrylamide (γ-FeOOH/KGM(Ga)/PNIPAM) thermosensitive hydrogel is proposed as the photocatalysts for extracting uranium from carbonate-containing uranium wastewater. The dynamic phase transformation is demonstrated to confirm the arbitrary transition of γ-FeOOH/KGM(Ga)/PNIPAM thermosensitive hydrogel from a dispersed state with a high specific surface area at low temperatures to a stable aggregated state at high temperatures. Notably, the γ-FeOOH/KGM(Ga)/PNIPAM thermosensitive hydrogel achieves a remarkably high rate of 92.3% in the removal of uranium from the wastewater containing carbonates and maintains the efficiency of uranium removal from uranium mine wastewater at over 90%. Relying on electron spin resonance and free radical capture experiment, we reveal the adsorption-reduction-nucleation-crystallization mechanism of uranium on γ-FeOOH/KGM(Ga)/PNIPAM thermosensitive hydrogel. Overall, this strategy provides a promising solution to treating uranium-contaminated wastewater, showing a massive potential in water purification.

Advanced materials for micro/nanorobotics

Autonomous micro/nanorobots capable of performing programmed missions are at the forefront of next-generation micromachinery. These small robotic systems are predominantly constructed using functional components sourced from micro- and nanoscale materials; therefore, combining them with various advanced materials represents a pivotal direction toward achieving a higher level of intelligence and multifunctionality. This review provides a comprehensive overview of advanced materials for innovative micro/nanorobotics, focusing on the five families of materials that have witnessed the most rapid advancements over the last decade: two-dimensional materials, metal-organic frameworks, semiconductors, polymers, and biological cells. Their unique physicochemical, mechanical, optical, and biological properties have been integrated into micro/nanorobots to achieve greater maneuverability, programmability, intelligence, and multifunctionality in collective behaviors. The design and fabrication methods for hybrid robotic systems are discussed based on the material categories. In addition, their promising potential for powering motion and/or (multi-)functionality is described and the fundamental principles underlying them are explained. Finally, their extensive use in a variety of applications, including environmental remediation, (bio)sensing, therapeutics, etc., and remaining challenges and perspectives for future research are discussed.

On-the-Fly Monitoring of the Capture and Removal of Nanoplastics with Nanorobots

Nanoplastics are considered an emerging organic persistent pollutant with possible severe long-term implications for the environment and human health; therefore, their remediation is of paramount importance. However, detecting and determining the concentration of nanoparticles in water is challenging and time-consuming due to their small size. In this work, we present a universal yet simple method for the detection and quantification of nanoplastics to monitor their removal from water using magnetic nanorobots. Nanoplastics were stained with a hydrophobic fluorescent dye to enable the use of photoluminescence techniques for their detection and quantification. Magnetic nanorobotic tools were employed to capture and subsequently remove the nanoplastics from contaminated waters. We demonstrated that nanorobots can capture and remove more than 90% of the nanoplastics from an aqueous solution within 120 min. This work shows that easy-to-use common fluorescent dyes combined with photoluminescence spectroscopy methods can be used as an alternative method for the detection and quantification of nanoplastics in water environments and swarming magnetic nanorobots for efficient capture and removal. These methods hold great potential for future research to improve the quantification and removal of nanoplastics in water, and it will ultimately reduce their harmful impact on the environment and human health.

Photoexcitation-induced efficient detoxification and removal of arsenite in contaminated water by a layered double hydroxide-supported polyacrylate stabilized ferrous sulfide composite

The effective detoxification and removal of arsenite (As(III)) has been widely concerned because of its strong toxicity and migration ability. In this study, we designed a layered double hydroxide-supported polyacrylate stabilized ferrous sulfide composite (PAA/FeS@LDH) and coupled it with UV excitation to purify As(III)-polluted water. The removal efficiency of As(III) under UV irradiation reached almost 100% in 120 min, and the first-order kinetic constant was 3.12 orders of magnitude higher than under dark. UV irradiation significantly accelerated the oxidation and detoxification of As(III) at the interface of PAA/FeS@LDH and treatment solution. It is attributable to the generation of reactive oxygen species (ROS) intermediates, including .O2-, .OH, and SO4.- under UV irradiation, because of the presence of the photogenerated electron-hole pairs and iron valence states cycles. Importantly, .O2- may be rapidly captured and oxidized to 1O2 on the surface of PAA/FeS@LDH that is also an important contributor to the oxidation removal of As(III). Noticeably, As(III) concentrations in the real water were rapidly reduced to below the guideline limitation of drinking water (10 μg/L) within 20 min under UV irradiation. Our outcomes provide a novel photoexcitation treatment system for the efficient detoxification and removal of As from actual wastewater.

Modulating nanostructures with polyvinylpyrrolidone: Design and development of a porous, biocompatible, and pH-Stable core-shell magnetic microrobot for demonstrating drug absorption from wastewater

Increased antineoplastic drug concentrations in wastewater stem from ineffective treatment plants and increased usage. Although microrobots are promising for pollutant removal, they face hurdles in developing a superstructure with superior adsorption capabilities, biocompatibility, porosity, and pH stability. This study focused on adjusting the PVP concentration from 0.05 to 0.375 mM during synthesis to create a favorable CMOC structure for drug absorption. Lower PVP concentrations (0.05 mM) yielded a three-dimensional nanoflower structure of CaMoO4 and CuS nanostructures, whereas five-fold concentrations (0.25 mM) produced a porous structure with a dense CuS core encased in a transparent CaMoO4 shell. The magnetically movable and pH-stable COF@CMOC microrobot, achieved by attaching CMOC to cobalt ferrite (CoF) NPs, captured doxorubicin efficiently, with up to 57 % efficiency at 200 ng/mL concentration for 30 min, facilitated by electrostatic interaction, hydrogen bonding, and pore filling of DOX. The results demonstrated that DOX removal through magnetic motion showed superior performance, with an estimated improvement of 57% compared to stirring conditions (17 %). A prototype PDMS microchannel system was developed to study drug absorption and microrobot recovery. The CaMoO4 shell of the microrobots exhibited remarkable robustness, ensuring long-lasting functionality in harsh wastewater environments and improving biocompatibility while safeguarding the CuS core from degradation. Therefore, microrobots are a promising eco-friendly solution for drug extraction. These microrobots show promise for the selective removal of doxorubicin from contaminated wastewater.

Bimetallic Photo-Activated and Steerable Janus Micromotors as Active Microcleaners for Wastewater

Photoactive colloidal motors whose motion can be controlled and even programed via external magnetic fields have significant potential in practical applications extending from biomedical fields to environmental remediation. Herein, we report a "three in one" strategy in a Co/Zn-TPM (3-trimethoxysilyl propyl methacrylate) bimetallic Janus colloidal micromotor (BMT-micromotor) which can be controlled by an optical field, chemical fuel, and magnetic field. The speed of the micromotors can be tuned by light intensity and with the concentration of the chemical fuel of H2O2, while it could be steered and programed through magnetic field due to the presence of Co in the bimetallic part. Finally, the BMT-micromotors were employed to effectively remove rubidium metal ions and organic dyes (methylene blue and rhodamine b). Benefited of excellent mobility, multiple active sites, and hierarchical morphology, the micromotors exhibit excellent adsorption capacity of 103 mg·g-1 to Rb metal ions and high photodegradation efficiency toward organic dyes in the presence of a lower concentration of H2O2. The experimental characterizations and DFT calculations confirmed the strong interaction of Rb metal ions on the surface of BMT-micromotors and the excellent decomposition of H2O2 which enhanced the photodegradation process. We expect the combination of light and fuel sensitivity with magnetic controllability to unlock an excess of opportunities for the application of BMT-micromotors in water treatments.

Recent advances of copolymer for water treatment

Increasing water pollution due to anthropogenic activities prompts the quest for an effective water treatment method. Polymeric materials have gained attention as adsorbents for water purification. Membranes are majorly made from homopolymeric materials. However, recent studies have focused on using copolymeric materials for improved performance. In this review, the basics of copolymerization including various types of copolymers, synthetic approaches, and their applications in various water pollutants removal are discussed in detail. Advances in water treatment technology using copolymeric materials as adsorbent/membranes in the last 4 years are covered with insights into the future outlook and areas of improvement in terms of copolymer composites for water treatment. Studies from the literature did not only reveal effectiveness of copolymer as a flocculant/antifouling materials and in removal of selective toxic metals, oil, and microbes but also demonstrated recyclability of the copolymer sorbents/membrane. Full exploration of unique copolymer textural and structural properties could lead to great advancement in water treatment process. PRACTITIONER POINTS: The copolymer types and synthetic methods are discussed. Application of copolymer as adsorbent/membranes for water treatment is presented. Recent advances show good pollutants removal for toxic metals, oil, and organics. Copolymer composites have great potential as adsorbent/membranes for future use in water treatment processes.

Nanocrystal Assemblies: Current Advances and Open Problems

We explore the potential of nanocrystals (a term used equivalently to nanoparticles) as building blocks for nanomaterials, and the current advances and open challenges for fundamental science developments and applications. Nanocrystal assemblies are inherently multiscale, and the generation of revolutionary material properties requires a precise understanding of the relationship between structure and function, the former being determined by classical effects and the latter often by quantum effects. With an emphasis on theory and computation, we discuss challenges that hamper current assembly strategies and to what extent nanocrystal assemblies represent thermodynamic equilibrium or kinetically trapped metastable states. We also examine dynamic effects and optimization of assembly protocols. Finally, we discuss promising material functions and examples of their realization with nanocrystal assemblies.

Review of carbon dot-hydrogel composite material as a future water-environmental regulator

As water pollution and scarcity pose severe threats to the sustainable progress of human society, it is important to develop a method or materials that can accurately and efficiently detect pollutants and purify aquatic environments or exploit marine resources. The compositing of photoluminescent and hydrophilic carbon dots (CDs) with hydrogels bearing three-dimensional networks to form CD-hydrogel composites to protect aquatic environments is a "win-win" strategy. Herein, the feasibility of the aforementioned method has been demonstrated. This paper reviews the recent progress of CD-hydrogel materials used in aquatic environments. First, the synthesis methods for these composites are discussed, and then, the composites are categorized according to different methods of combining the raw materials. Thereafter, the progress in research on CD-hydrogel materials in the field of water quality detection and purification is reviewed in terms of the application of the mechanisms. Finally, the current challenges and prospects of CD-hydrogel materials are described. These results are expected to provide insights into the development of CD-hydrogel composites for researchers in this field.

Methamphetamine Removal from Aquatic Environments by Magnetic Microrobots with Cyclodextrin Chiral Recognition Elements

The growing consumption of drugs of abuse together with the inefficiency of the current wastewater treatment plants toward their presence has resulted in an emergent class of pollutants. Thus, the development of alternative approaches to remediate this environmental threat is urgently needed. Microrobots, combining autonomous motion with great tunability for the development of specific tasks, have turned into promising candidates to take on the challenge. Here, hybrid urchin-like hematite (α-Fe2O3) microparticles carrying magnetite (Fe3O4) nanoparticles and surface functionalization with organic β-cyclodextrin (CD) molecules are prepared with the aim of on-the-fly encapsulation of illicit drugs into the linked CD cavities of moving microrobots. The resulting mag-CD microrobots are tested against methamphetamine (MA), proving their ability for the removal of this psychoactive substance. A dramatically enhanced capture of MA from water with active magnetically powered microrobots when compared with static passive CD-modified particles is demonstrated. This work shows the advantages of enhanced mass transfer provided by the externally controlled magnetic navigation in microrobots that together with the versatility of their design is an efficient strategy to clean polluted waters.

Magnetic Microrobot Swarms with Polymeric Hands Catching Bacteria and Microplastics in Water

The forefront of micro- and nanorobot research involves the development of smart swimming micromachines emulating the complexity of natural systems, such as the swarming and collective behaviors typically observed in animals and microorganisms, for efficient task execution. This study introduces magnetically controlled microrobots that possess polymeric sequestrant "hands" decorating a magnetic core. Under the influence of external magnetic fields, the functionalized magnetic beads dynamically self-assemble from individual microparticles into well-defined rotating planes of diverse dimensions, allowing modulation of their propulsion speed, and exhibiting a collective motion. These mobile microrobotic swarms can actively capture free-swimming bacteria and dispersed microplastics "on-the-fly", thereby cleaning aquatic environments. Unlike conventional methods, these microrobots can be collected from the complex media and can release the captured contaminants in a second vessel in a controllable manner, that is, using ultrasound, offering a sustainable solution for repeated use in decontamination processes. Additionally, the residual water is subjected to UV irradiation to eliminate any remaining bacteria, providing a comprehensive cleaning solution. In summary, this study shows a swarming microrobot design for water decontamination processes.

Dual-Responsive Nanorobot-Based Marsupial Robotic System for Intracranial Cross-Scale Targeting Drug Delivery

Nanorobots capable of active movement are an exciting technology for targeted therapeutic intervention. However, the extensive motion range and hindrance of the blood-brain barrier impeded their clinical translation in glioblastoma therapy. Here, a marsupial robotic system constructed by integrating chemical/magnetic hybrid nanorobots (child robots) with a miniature magnetic continuum robot (mother robot) for intracranial cross-scale targeting drug delivery is reported. For primary targeting on macroscale, the continuum robot enters the cranial cavity through a minimally invasive channel (e.g., Ommaya device) in the skull and transports the nanorobots to pathogenic regions. Upon circumventing the blood-brain barrier, the released nanorobots perform secondary targeting on microscale to further enhance the spatial resolution of drug delivery. In vitro experiments against primary glioblastoma cells derived from different patients are conducted for personalized treatment guidance. The operation feasibility within organisms is shown in ex vivo swine brain experiments. The biosafety of the treatment system is suggested in in vivo experiments. Owing to the hierarchical targeting method, the targeting rate, targeting accuracy, and treatment efficacy have improved greatly. The marsupial robotic system offers a novel intracranial local therapeutic strategy and constitutes a key milestone in the development of glioblastoma treatment platforms.

Innovations in chemical degradation technologies for the removal of micro/nano-plastics in water: A comprehensive review

Micro/nanoplastics (M/NPs) in water have raised global concern due to their potential environmental risks. To reestablish a M/NPs free world, enormous attempts have been made toward employing chemical technologies for their removal in water. This review comprehensively summarizes the advances in chemical degradation approaches for M/NPs elimination. It details and discusses promising techniques, including photo-based technologies, Fenton-based reaction, electrochemical oxidation, and novel micro/nanomotors approaches. Subsequently, critical influence factors, such as properties of M/NPs and operating factors, are analyzed in this review specifically. Finally, it concludes by addressing the current challenges and future perspectives in chemical degradation. This review will provide guidance for scientists to further explore novel strategies and develop feasible chemical methods for the improved control and remediation of M/NPs in the future.

Hierarchical hollow α-Fe2O3/ZnFe2O4/Mn2O3 Janus micromotors as dynamic and efficient microcleaners for enhanced photo-Fenton elimination of organic pollutants

Micro/nanomotors that can promote mass transport have attracted more and more research concern in the photocatalysis field. Here we first report a newly-designed hierarchical α-Fe2O3/ZnFe2O4/Mn2O3 magnetic micromotor as a heterogeneous photocatalyst for the degradation of cationic dye methylene blue (MB) from wastewater. The resulting three-dimensional (3D) flower-like hollow Janus micromotors are fabricated through a green and scalable strategy, in which each component has different functions. ZnFe2O4 microspheres serve as a magnetic scaffold for the nucleation and growth of α-Fe2O3 nanosheets and for the recycling of the micromachine. α-Fe2O3 nanosheets have shown great potential as an ideal semiconductor material for the photocatalytic decontamination of pollutants. Mn2O3 nanoparticles are mainly utilized as a catalyst to produce O2 bubbles to propel the autonomic movement of the micromotors in the presence of H2O2 fuel and also as a Fenton-like catalyst to decompose H2O2 to generate reactive oxygen species. Furthermore, the resultant micromotors exhibited linear-like motion form with an average speed of 189.1 μm s-1 in 5 wt% H2O2 solution. Moreover, the self-driven micromotors exhibited a superior catalytic degradation property toward MB, which was attributed to the synergistic effect of heterogeneous photocatalyst and the boosted micro-mixing and mass transfer caused by the vigorous motion of the micro-actuator. The possible degradation intermediates and passways of MB by α-Fe2O3/ZnFe2O4/Mn2O3 micromotor were identified with time of flight mass spectroscopy (TOF-MS). The 3D Janus micromotors have the potential to be used as a high-efficiency and active heterogeneous photocatalyst for the degradation of organic pollutants.

Designing self-triggered micro/milli devices for gastrointestinal tract drug delivery

INTRODUCTION

Self-triggered micro-/milli-devices (STMDs), which are artificial devices capable of responding to the surrounding environment and transferring external energy into kinetic energy, thus realizing autonomous movement, have come to the forefront as a powerful tool in cargo delivery via gastrointestinal tract. Urgent needs have been raised to overview the development of this area.

AREAS COVERED

We summarize the advancement of designing STMDs for delivery via gastrointestinal tract. We first give a brief overview on the opportunities and challenges of delivery via gastrointestinal tract involving gastric barriers and intestinal barriers. Then, emphasis is laid on the design and applications of STMDs for delivery via gastrointestinal tract. We focus on their morphological characteristics and function design, expounding their working mechanisms in the complex gastrointestinal tract.

EXPERT OPINION

Although with much progress in STMDs, there is still a huge gap between laboratory researches and clinical applications due to some limitations including latent digestive burden, sophisticated fabrication, unstable delivery, and so on. We give a discussion on the potential, challenges, and prospects of developing STMDs for delivery via gastrointestinal tract.

Sunlight propelled two-dimensional nanorobots with enhanced mechanical damage of bacterial membrane

Bacterial pollution in water sources poses a serious threat to human health and causes a water crisis. To treat it efficiently and ecologically, many studies have explored the antibacterial properties of two-dimensional nanomaterials in water, but their static antibacterial modes limit their effectiveness. In this work, we designed a facile and effective antibacterial nanorobots by loading super small gold nanorods (sAuNR) onto the surface of MXene nanosheets (MXene@sAuNR). The plasmon resonance effect of sAuNR can enhance the optical absorption cross section of the nanorobots, thereby improving their motion ability under irradiation and then causing cell membrane mechanical damage to bacteria. Our research proved that nanorobots with good optical driving characteristics displayed gratifying antibacterial properties even at ultra-low concentration as 5 µg/mL within 30 min. Furthermore, the nanorobots showed satisfactory antibacterial efficiency in real river samples under sunlight irradiation. These nanorobots presented in this study provides valuable insights towards designing self-energy collection and self-driving antibacterial materials that overcome the shortcomings of conventional static antibacterial methods. As sunlight is the cheapest and natural light source, these nanorobots have opened an effective and sustainable way for large-scale treatment of bacterial pollution in water.

From Nanoscopic to Macroscopic Materials by Stimuli-Responsive Nanoparticle Aggregation

Stimuli-responsive nanoparticle (NP) aggregation plays an increasingly important role in regulating NP assembly into microscopic superstructures, macroscopic 2D, and 3D functional materials. Diverse external stimuli are widely used to adjust the aggregation of responsive NPs, such as light, temperature, pH, electric, and magnetic fields. Many unique structures based on responsive NPs are constructed including disordered aggregates, ordered superlattices, structural droplets, colloidosomes, and bulk solids. In this review, the strategies for NP aggregation by external stimuli, and their recent progress ranging from nanoscale aggregates, microscale superstructures to macroscale bulk materials along the length scales as well as their applications are summarized. The future opportunities and challenges for designing functional materials through NP aggregation at different length scales are also discussed.

Fish-like magnetic microrobots for microparts transporting at liquid surfaces

Magnetic microrobots have tremendous potential applications due to their wireless actuation and fast response in confined spaces. Herein, inspired by fish, a magnetic microrobot working at liquid surfaces was proposed in order to transport microparts effectively. Different from other fish-like robots propelled by flexible caudal fins, the microrobot is designed as a simple sheet structure with a streamlined shape. It is fabricated monolithically utilizing polydimethylsiloxane doped with magnetic particles. The unequal thicknesses of different parts of the fish shape enable the microrobot to move faster via a liquid level difference around the body under an oscillating magnetic field. The propulsion mechanism is investigated through theoretical analysis and simulations. The motion performance characteristics are further characterized through experiments. It is interesting to find that the microrobot moves in a head-forward mode when the vertical magnetic field component is upward, whereas it moves in a tail-forward mode when the component is downward. Relying on the modulation of capillary forces, the microrobot is able to capture and deliver microballs along a given path. The maximum transporting speed can reach 1.2 mm s^-1, which is about three times the microball diameter per second. It is also found that the transporting speed with the microball is much higher than that of the microrobot alone. The reason for this is that when the micropart and microrobot combine, the increased asymmetry of the liquid surfaces caused by the forward movement of the gravity center can increase the forward driving force. The proposed microrobot and the transporting method are expected to have more applications in micromanipulation fields.

A Dual-Biomineralized Yeast Micro-/Nanorobot with Self-Driving Penetration for Gastritis Therapy and Motility Recovery

Micro-/nanorobots have attracted great interest in the field of drug delivery and treatment, while preparations for biocompatible robots are extremely challenging. Here, a self-driving yeast micro-/nanorobot (Cur@CaY-robot) is designed via dual biomineralization and acid catalysis of calcium carbonate (CaCO₃). Inner nano-CaCO₃ inside yeast cells (CaY) is biomineralized through cell respiration and provides nanoscaffolds for highly encapsulating curcumin (Cur). Meanwhile, the CaCO₃ crystals outside yeast cells (outer-CaCO₃) through uniaxial growth offer an asymmetric power source for self-propelled motility. The Cur@CaY-robot displays an efficient motion in gastric acid, with the potential for deep penetration to the thick gastric mucus, which significantly improves the accumulation of drug agents in the stomach wall tissue for robust gastritis therapy. More importantly, Ca²⁺ cations released from the Cur@CaY-robot also synergistically repair the gastric motility of gastritis mice. Such yeast micro-/nanorobots exhibit desirable biocompatibility and biodegradability with a good loading capacity for drugs. This work provides an idea for the design of micro-/nanorobots through an environmentally friendly biosynthesis strategy for active drug delivery and precise therapy.

Magnetically Driven Self-Degrading Zinc-Containing Cystine Microrobots for Treatment of Prostate Cancer

Prostate cancer is the most commonly diagnosed tumor disease in men, and its treatment is still a big challenge in standard oncology therapy. Magnetically actuated microrobots represent the most promising technology in modern nanomedicine, offering the advantage of wireless guidance, effective cell penetration, and non-invasive actuation. Here, new biodegradable magnetically actuated zinc/cystine-based microrobots for in situ treatment of prostate cancer cells are reported. The microrobots are fabricated via metal-ion-mediated self-assembly of the amino acid cystine encapsulating superparamagnetic Fe₃ O₄ nanoparticles (NPs) during the synthesis, which allows their precise manipulation by a rotating magnetic field. Inside the cells, the typical enzymatic reducing environment favors the disassembly of the aminoacidic chemical structure due to the cleavage of cystine disulfide bonds and disruption of non-covalent interactions with the metal ions, as demonstrated by in vitro experiments with reduced nicotinamide adenine dinucleotide (NADH). In this way, the cystine microrobots served for site-specific delivery of Zn²⁺ ions responsible for tumor cell killing via a "Trojan horse effect". This work presents a new concept of cell internalization exploiting robotic systems' self-degradation, proposing a step forward in non-invasive cancer therapy.

Light-powered swarming phoretic antimony chalcogenide-based microrobots with "on-the-fly" photodegradation abilities

Microrobots are at the forefront of research for biomedical and environmental applications. Whereas a single microrobot exhibits quite low performance in the large-scale environment, swarms of microrobots are representing a powerful tool in biomedical and environmental applications. Here, we fabricated phoretic Sb₂S₃-based microrobots that exhibited swarming behavior under light illumination without any addition of chemical fuel. The microrobots were prepared in an environmentally friendly way by reacting the precursors with bio-originated templates in aqueous solution in a microwave reactor. The crystalline Sb₂S₃ material provided the microrobots with interesting optical and semiconductive properties. Because of the formation of reactive oxygen species (ROS) upon light illumination, the microrobots possessed photocatalytic properties. To demonstrate the photocatalytic abilities, industrially used dyes, quinoline yellow and tartrazine were degraded using microrobots in the "on-the-fly" mode. Overall, this proof-of-concept work showed that Sb₂S₃ photoactive material is suitable for designing swarming microrobots for environmental remediation applications.

Lithographic Microneedle-Motors from Multimodal Microfluidics for Cargo Delivery

Micromotors have led to an unprecedented revolution in the field of cargo delivery. Attempts in this area trend toward enriching their structures and improving their functions to promote their further applications. Herein, novel microneedle-motors (MNMs) for active drug delivery through a flexible multimodal microfluidic lithographic approach are presented. The multimodal microfluidics is composed of a co-flow geometry-derived droplet fluid and an active cargo mixed laminar flow in a triangular microchannel. The MNMs with sharp tips and spherical fuel-loading cavities are obtained continuously from microfluidics with the assistance of flow lithography. The structural parameters of the MNMs could be precisely tailored by simply choosing the flow speed or the shape of the photomask. As the actives are mixed into the phase solution during the generation, the resultant MNMs are loaded with cargoes for direct applications without any extra complex operation. Based on these features, it is demonstrated that with sharp tips and autonomous movement, the MNMs can efficiently penetrate the tissue-like substrates, indicating the potential in overcoming physiological barriers for cargo release. These results indicate that the proposed multimodal microfluidic lithographic MNMs are valuable for practical active cargo delivery in biomedical and other relative areas.

Radiopaque Nanorobots as Magnetically Navigable Contrast Agents for Localized In Vivo Imaging of the Gastrointestinal Tract

Magnetic nanorobots offer wireless navigation capability in hard-to-reach areas of the human body for targeted therapy and diagnosis. Though in vivo imaging is required for guidance of the magnetic nanorobots toward the target areas, most of the imaging techniques are inadequate to reveal the potential locomotion routes. This work proposes the use of radiopaque magnetic nanorobots along with microcomputed tomography (microCT) for localized in vivo imaging applications. The nanorobots consist of a contrast agent, barium sulfate (BaSO₄ ), magnetized by the decoration of magnetite (Fe₃ O₄ ) particles. The magnetic features lead to actuation under rotating magnetic fields and enable precise navigation in a microfluidic channel used to simulate confined spaces of the body. In this channel, the intrinsic radiopacity of the nanorobots also provides the possibility to reveal the internal structures by X-ray contrast. Furthermore, in vitro analysis indicates nontoxicity of the nanorobots. In vivo experiments demonstrate localization of the nanorobots in a specific part of the gastrointestinal (GI) tract upon the influence of the magnetic field, indicating the efficient control even in the presence of natural peristaltic movements. The nanorobots reported here highlight that smart nanorobotic contrast agents can improve the current imaging-based diagnosis techniques by providing untethered controllability in vivo.

Smart Nanoparticle-Based Platforms for Regulating Tumor Microenvironment and Cancer Immunotherapy

Tumor development and metastasis are closely related to the tumor microenvironment (TME). Recently, several studies indicate that modulating TME can enhance cancer immunotherapy. Among various approaches to modulating TME, nanoparticles (NPs) with unique inherent advantages and smart modified characteristics are promising candidates in delivering drugs to cancer cells, amplifying the therapeutic effects, and leading to a cascade of immune responses. In this review, several smart NP-based platforms are briefly introduced, such as responsive NPs, targeting NPs, and the composition of TME, including dendritic cells, macrophages, fibroblasts, endothelial cells, myeloid-derived suppressor cells, and regulatory T cells. Moreover, the recent applications of smart NP-based platforms in regulating TME and cancer immunotherapy are briefly introduced. Last, the advantages and disadvantages of these smart NP-based platforms in potential clinical translation are discussed.

Rotary biomolecular motor-powered supramolecular colloidal motor

Cells orchestrate the motion and force of hundreds of protein motors to perform various mechanical tasks over multiple length scales. However, engineering active biomimetic materials from protein motors that consume energy to propel continuous motion of micrometer-sized assembling systems remains challenging. Here, we report rotary biomolecular motor-powered supramolecular (RBMS) colloidal motors that are hierarchically assembled from a purified chromatophore membrane containing F_OF₁-ATP synthase molecular motors, and an assembled polyelectrolyte microcapsule. The micro-sized RBMS motor with asymmetric distribution of F_OF₁-ATPases can autonomously move under light illumination and is collectively powered by hundreds of rotary biomolecular motors. The propulsive mechanism is that a transmembrane proton gradient generated by a photochemical reaction drives F_OF₁-ATPases to rotate for ATP biosynthesis, which creates a local chemical field for self-diffusiophoretic force. Such an active supramolecular architecture endowed with motility and biosynthesis offers a promising platform for intelligent colloidal motors resembling the propulsive units in swimming bacteria.

Magnetically boosted 1D photoactive microswarm for COVID-19 face mask disruption

The recent COVID-19 pandemic has resulted in the massive discard of pandemic-related plastic wastes, causing serious ecological harm and a high societal burden. Most single-use face masks are made of synthetic plastics, thus their careless disposal poses a direct threat to wildlife as well as potential ecotoxicological effects in the form of microplastics. Here, we introduce a 1D magnetic photoactive microswarm capable of actively navigating, adhering to, and accelerating the degradation of the polypropylene microfiber of COVID-19 face masks. 1D microrobots comprise an anisotropic magnetic core (Fe3O4) and photocatalytic shell (Bi2O3/Ag), which enable wireless magnetic maneuvering and visible-light photocatalysis. The actuation of a programmed rotating magnetic field triggers a fish schooling-like 1D microswarm that allows active interfacial interactions with the microfiber network. The follow-up light illumination accelerates the disruption of the polypropylene microfiber through the photo-oxidative process as corroborated by morphological, compositional, and structural analyses. The active magnetic photocatalyst microswarm suggests an intriguing microrobotic solution to treat various plastic wastes and other environmental pollutants.

Water-Immiscible Coacervate as a Liquid Magnetic Robot for Intravascular Navigation

Developing magnetic ultrasoft robots to navigate through extraordinarily narrow and confined spaces like capillaries in vivo requires synthesizing materials with excessive deformability, responsive actuation, and rapid adaptability, which are difficult to achieve with the current soft polymeric materials, such as elastomers and hydrogels. We report a magnetically actuatable and water-immiscible (MAWI) coacervate based on the assembled magnetic core-shell nanoparticles to function as a liquid robot. The degradable and biocompatible millimeter-sized MAWI coacervate liquid robot can remain stable under changing pH and salt concentrations, release loaded cargoes on demand, squeeze through an artificial capillary network within seconds, and realize intravascular targeting in vivo guided by an external magnetic field. We believe the proposed "coacervate-based liquid robot" can implement demanding tasks beyond the capability of conventional elastomer or hydrogel-based soft robots in the field of biomedicine and represents a distinct design strategy for high-performance ultrasoft robots.

Precisely Navigated Biobot Swarms of Bacteria Magnetospirillum magneticum for Water Decontamination

Hybrid biological robots (biobots) prepared from living cells are at the forefront of micro-/nanomotor research due to their biocompatibility and versatility toward multiple applications. However, their precise maneuverability is essential for practical applications. Magnetotactic bacteria are hybrid biobots that produce magnetosome magnetite crystals, which are more stable than synthesized magnetite and can orient along the direction of earth's magnetic field. Herein, we used Magnetospirillum magneticum strain AMB-1 (M. magneticum AMB-1) for the effective removal of chlorpyrifos (an organophosphate pesticide) in various aqueous solutions by naturally binding with organic matter. Precision control of M. magneticum AMB-1 was achieved by applying a magnetic field. Under a programed clockwise magnetic field, M. magneticum AMB-1 exhibit swarm behavior and move in a circular direction. Consequently, we foresee that M. magneticum AMB-1 can be applied in various environments to remove and retrieve pollutants by directional control magnetic actuation.

Smart micro- and nanorobots for water purification

Less than 1% of Earth's freshwater reserves is accessible. Industrialization, population growth and climate change are further exacerbating clean water shortage. Current water-remediation treatments fail to remove most pollutants completely or release toxic by-products into the environment. The use of self-propelled programmable micro- and nanoscale synthetic robots is a promising alternative way to improve water monitoring and remediation by overcoming diffusion-limited reactions and promoting interactions with target pollutants, including nano- and microplastics, persistent organic pollutants, heavy metals, oils and pathogenic microorganisms. This Review introduces the evolution of passive micro- and nanomaterials through active micro- and nanomotors and into advanced intelligent micro- and nanorobots in terms of motion ability, multifunctionality, adaptive response, swarming and mutual communication. After describing removal and degradation strategies, we present the most relevant improvements in water treatment, highlighting the design aspects necessary to improve remediation efficiency for specific contaminants. Finally, open challenges and future directions are discussed for the real-world application of smart micro- and nanorobots.

Tailoring Functional Micromotors for Sensing

Micromotors are identified as a promising candidate in the field of sensing benefiting from their capacity of autonomous movement. Here, a review on the development of tailoring micromotors for sensing is presented, covering from their propulsion mechanisms and sensing strategies to applications. First, we concisely summarize the propulsion mechanism of micromotors involving fuel-based propulsion and fuel-free propulsion introducing their principles. Then, emphasis is laid to the sensing stratagems of the micromotors including speed-based sensing strategy, fluorescence-based sensing strategy, and other strategies. We listed typical examples of different sensing stratagems. After that, we introduce the applications of micromotors in sensing fields including environmental science, food safety, and biomedical fields. Finally, we discuss the challenges and prospects of the micromotors tailored for sensing. We believe that this comprehensive review can help readers to catch the research frontiers in the field of sensing and thus to burst out new ideas.

Soft Magnetic Microrobots for Photoactive Pollutant Removal

"Soft" robotics based on hydrogels appears as an alternative to the traditional technology of "hard" robotics. Soft microrobots are employed for drug delivery and cell manipulation. This work develops magnetic hydrogel-based microrobots using chitosan (CHI) as the body of the micromotor and Fe₃ O₄ nanoparticles to allow for its magnetic actuation. In addition, ZnO nanoparticles are incorporated inside the CHI body of the microrobot to act as an active component for pollutants photodegradation. CHI@Fe₃ O₄ -ZnO microrobots are used for the efficient photodegradation of persistent organic pollutants (POPs). The high absorption of CHI hydrogel enhances the POP photodegradation, degrading it 75% in just 30 min. The adsorption-degradation and magnetic properties of CHI@Fe₃ O₄ -ZnO microrobots are used in five cycles while maintaining up to 60% photodegradation efficiency. The proof-of-concept present in this work represents a simple way to obtain soft microrobots with magnetic actuation and photodegradation functionalities for several water purification applications.

Self-Propelled Magnetic Dendrite-Shaped Microrobots for Photodynamic Prostate Cancer Therapy

Photocatalytic micromotors that exhibit wireless and controllable motion by light have been extensively explored for cancer treatment by photodynamic therapy (PDT). However, overexpressed glutathione (GSH) in the tumor microenvironment can down-regulate the reactive oxygen species (ROS) level for cancer therapy. Herein, we present dendrite-shaped light-powered hematite microrobots as an effective GSH depletion agent for PDT of prostate cancer cells. These hematite microrobots can display negative phototactic motion under light irradiation and flexible actuation in a defined path controlled by an external magnetic field. Non-contact transportation of micro-sized cells can be achieved by manipulating the microrobot's motion. In addition, the biocompatible microrobots induce GSH depletion and greatly enhance PDT performance. The proposed dendrite-shaped hematite microrobots contribute to developing dual light/magnetic field-powered micromachines for the biomedical field.

Swarming Magnetically Navigated Indigo-Based Hydrophobic Microrobots for Oil Removal

Removal of oil is very important for environmental remediation when considering its negative impacts on living organisms and on the quality of water, groundwater, and soil. Here, we report on the application of hydrophobic magnetic hydrogen-bonded organic pigment-based microrobots for oil removal. The microrobots can be wirelessly navigated in a transversal rotating magnetic field, with full control of their trajectory. In addition, the velocity of magnetic microrobots can be easily controlled by changing the frequency. Due to their hydrophobic nature, the microrobots were able to enter droplets of spilled oil. Consequently, the navigation of the oil droplets was enabled in a magnetic field. Moreover, the microrobots captured within the oil droplets exhibited a swarm-like behavior; they collectively navigated toward further oil droplets that were collected and transferred to a desired location. This concept does not require the use of any additional fuel or surfactants, which is crucial for large-scale oil pollution treatment. Therefore, we believe that these microrobot swarms have great potential in remediating aqueous environments.

Water reuse in industries: analysis of opportunities in the Paraíba do Sul river basin, a case study in Presidente Vargas Plant, Brazil

In recent years, the demand for clean water has been growing all over the world despite the different threats posed, including increasing pollution, increasing deforestation and climate change. Industrial activity is the second largest consumer of water, so highly industrialized regions are more susceptible to water stress. In this sense, reuse strategies have been progressively discussed and used around the world; however, in Brazil there is still place for many advances, whether due to lack of incentives, cultural issues in society, or poor regulation of the subject. The objective of this work was to carry out a diagnosis of raw water uptake by industries in one Hydrographic Region of the state of Rio de Janeiro and to propose a discussion on the adoption of water reuse practices for non-potable purposes from the use of treated effluents. A survey of the theoretical framework on the subject was carried out, as well as an analysis of sustainability indicators and reports of the companies, including the current licensing processes of large undertakings consuming water resources. With this study, it was possible to obtain the average cost of implementing a water reuse unit for an industry in the state of Rio de Janeiro-Brazil, which, despite still being expensive, has a strong tendency to use due to world water shortages. Finally, it was concluded that the state of Rio de Janeiro has a threat of water scarcity that could be aggravated in the coming years, if measures and investments in supply alternatives are not adopted (water reuse), and improvement in all stages of water management water resources.

Hybrid Enzymatic/Photocatalytic Degradation of Antibiotics via Morphologically Programmable Light-Driven ZnO Microrobots

Antibiotics are antimicrobial substances that can be used for preventive and therapeutic purposes in humans and animals. Their overdose usage has led to uncontrolled release to the environment, contributing significantly to the development of antimicrobial resistance phenomena. Here, enzyme-immobilized self-propelled zinc oxide (ZnO) microrobots are proposed to effectively target and degrade the released antibiotics in water bodies. Specifically, the morphology of the microrobots is tailored via the incorporation of Au during the synthetic process to lead the light-controlled motion into having on/off switching abilities. The microrobots are further modified with laccase enzyme by physical adsorption, and the immobilization process is confirmed by enzymatic activity measurements. Oxytetracycline (OTC) is used as a model of veterinary antibiotics to investigate the enzyme-immobilized microrobots for their removal capacities. The results demonstrate that the presence of laccase on the microrobot surfaces can enhance the removal of antibiotics via oxidation. This concept for immobilizing enzymes on self-propelled light-driven microrobots leads to the effective removal of the released antibiotics from water bodies with an environmentally friendly strategy.

Magnetic Biohybrid Robots as Efficient Drug Carrier to Generate Plant Cell Clones

Micro/nanorobots represent a new generation of micromachines that can accomplish various tasks, such as loading and transporting specific targets or pharmaceuticals for a given application. Biohybrid robots consisting of biological cells (bacteria, sperm, and microalgae) combined with inorganic particles to control or propel their movement are of particular interest. The skeleton of these biohybrid robots can be used to load biomolecules. In this work, the authors create biohybrid robots based on tomato plants by coculturing ferromagnetic nanoparticles (Fe₃ O₄ ) with tomato callus cells. The tomato-based biohybrid robots (Tomato-Biobots) containing Fe₃ O₄ nanoparticles  are driven by a transversely rotating magnetic field. In addition, biohybrid robots are used to load vitamin C, to generate clones of tomato cells. It is shown that the presence of Fe₃ O₄  does not affect the growth of tomato callus. This study opens a wide range of possibilities for the use of biohybrid robots@Fe₃ O₄  to deliver conventional agrochemicals, including fertilizers, pesticides, and herbicides, and allows for a gradual and sustained release of nutrients and agrochemicals, leading to precise dosing that reduces the amount of agrochemicals used. This conceptually new type of micromachine with application to plants and agronomy shall find broad use in this field.

Shape-Controlled Self-Assembly of Light-Powered Microrobots into Ordered Microchains for Cells Transport and Water Remediation

Nature presents the collective behavior of living organisms aiming to accomplish complex tasks, inspiring the development of cooperative micro/nanorobots. Herein, the spontaneous assembly of hematite-based microrobots with different shapes is presented. Autonomous motile light-driven hematite/Pt microrobots with cubic and walnut-like shapes are prepared by hydrothermal synthesis, followed by the deposition of a Pt layer to design Janus structures. Both microrobots show a fuel-free motion ability under light irradiation. Because of the asymmetric orientation of the magnetic dipole moment in the crystal, cubic hematite/Pt microrobots can self-assemble into ordered microchains, contrary to the random aggregation observed for walnut-like microrobots. The microchains exhibit different synchronized motions under light irradiation depending on the mutual orientation of the individual microrobots during the assembly, which allows them to accomplish multiple tasks, including capturing, picking up, and transporting microscale objects, such as yeast cells and suspended matter in water extracted from personal care products, as well as degrading polymeric materials. Such light-powered self-assembled microchains demonstrate an innovative cooperative behavior for small-scale multitasking artificial robotic systems, holding great potential toward cargo capture, transport, and delivery, and wastewater remediation.