Rotating-Electric-Field-Induced Carbon-Nanotube-Based Nanomotor in Water: A Molecular Dynamics Study

Acidity-Actuated Polymer/Calcium Phosphate Hybrid Nanomotor (PCaPmotor) for Penetrating Drug Delivery and Synergistic Anticancer Immunotherapy

Tumor acidity-driven nanomotors may offer robust propulsion for tumor-specific penetrating drug delivery. Herein, an acidity-actuated poly(amino acid) calcium phosphate (CaP) hybrid nanomotor (PCaPmotor) was designed, using a mPEG-PAsp-PPhe@THZ531 micelle (Poly@THZ) for CaP mineralization accompanied by αPD-L1 antibody encapsulation. Dissolution of the CaP layer in an acidic tumor environment gave off heat energy to propel the nanomotor to augment the cellular uptake and penetration into deeply seated cancer cells while facilitating αPD-L1 release. THZ531 delivered by the PCaPmotor inhibited CDK12 and its down-streamed phosphorylation of RNAP-II to increase the cancer immunogenicity events such as the DNA damage, cell apoptosis, immunogenic cell death, lysosomal function disturbance, and MHC-I upregulation. THZ531 and αPD-L1 cosupplied by PCaPmotor significantly increased the frequency of DCs maturation and intratumoral infiltration of CTLs, but the two free drugs did not. Consequently, the PCaP@THZ/αPD-L1 nanomotor resulted in synergistic anticancer immunotherapy in mice. This acid-actuated PCaPmotor represented a new paradigm for penetrating drug delivery.

Visualizing Facets Asymmetry Induced Directional Movement of Cadmium Chloride Nanomotor

Nanomotors in solution have many potential applications. However, it has been a significant challenge to realize the directional motion of nanomotors. Here, we report cadmium chloride tetrahydrate (CdCl2·4H2O) nanomotors with remarkable directional movement under electron beam irradiation. Using in situ liquid phase transmission electron microscopy, we show that the CdCl2·4H2O nanoparticle with asymmetric surface facets moves through the liquid with the flat end in the direction of motion. As the nanomotor morphology changes, the speed of movement also changes. Finite element simulation of the electric field and fluid velocity distribution around the nanomotor assists the understanding of ionic self-diffusiophoresis as a driving force for the nanomotor movement; the nanomotor generates its own local ion concentration gradient due to different chemical reactivities on different facets.

Droplet Rolling Transport on Hydrophobic Surfaces Under Rotating Electric Fields: A Molecular Dynamics Study

Driving droplets by electric fields is usually achieved by controlling their wettability, and realizing a flexible operation requires complex electrode designs. Here, we show by molecular dynamics methods the droplet transport on hydrophobic surfaces in a rolling manner under a rotating electric field, which provides a simpler and promising way to manipulate droplets. The droplet internal velocity field shows the rolling mode. When the contact angle on the solid surface is 144.4°, the droplet can be transported steadily at a high velocity under the rotating electric field (E = 0.5 V nm-1, ω = π/20 ps-1). The droplet center-of-mass velocities and trajectories, deformation degrees, dynamic contact angles, and surface energies were analyzed regarding the electric field strength and rotational angular frequency. Droplet transport with a complex trajectory on a two-dimensional surface is achieved by setting the electric field, which reflects the programmability of the driving method. Nonuniform wettability stripes can assist in controlling droplet trajectories. The droplet transport on the three-dimensional surface is studied, and the critical conditions for the droplet passing through the surface corners and the motion law on the curved surface are obtained. Droplet coalescence has been achieved by surface designs.

Multi-Wavelength Light-Responsive Metal-Phenolic Network-Based Microrobots for Reactive Species Scavenging

Light-driven microrobots with different propulsion mechanisms have attracted great attention in microrobot synthesis and applications. However, current systems rely heavily on precious metals, using a complex synthesis process and limited working wavelength. It is therefore of great interest to fabricate microrobots that can be driven by multi-wavelength irradiation and with simple components. Here, metal-phenolic network (MPN)-based microrobots are synthesized using a sacrificial polystyrene bead template and an extra capping is added to regulate their symmetry. The hollow MPN microrobots with different layers of capping are capable of moving under both near-infrared (NIR) irradiation and ultraviolet (UV) irradiation, without fuel. The velocity of the microrobots under irradiation is altered by the thickness of the asymmetric capping and their motion could be manipulated remotely by switching the NIR or UV irradiation on and off. With light-driven mobility, the reactive oxygen and nitrogen species (RONS) scavenging activity of the microrobots is significantly increased. Therefore, this proposed microrobot system provides a synthesis strategy to develop asymmetric light-navigated microrobots for future medical treatment with tunable structure, multi-wavelength light-responsive mobility, and great RONS scavenging capacity.

Nanobots-based advancement in targeted drug delivery and imaging: An update

Manipulation and targeted navigation of nanobots in complex biological conditions can be achieved by chemical reactions, by applying external forces, and via motile cells. Several studies have applied fuel-based and fuel-free propulsion mechanisms for nanobots movements in environmental sciences and robotics. However, their applications in biomedical sciences are still in the budding phase. Therefore, the current review introduces the fundamentals of different propulsion strategies based on the advantageous features of applied nanomaterials or cellular components. Furthermore, the recent developments reported in various literatures on next-generation nanobots, such as Xenobots with applications of in-vitro and in-vivo drug delivery and imaging were also explored in detail. The challenges and the future prospects are also highlighted with corresponding advantages and limitations of nanobots in biomedical applications. This review concludes that with ever booming research enthusiasm in this field and increasing multidisciplinary cooperation, micro-/nanorobots with intelligence and multifunctions will emerge in the near future, which would have a profound impact on the treatment of diseases.

Biosafety, Functionalities, and Applications of Biomedical Micro/nanomotors

Due to their unique ability to actively move, micro/nanomotors offer the possibility of breaking through the limitations of traditional passive drug delivery systems for the treatment of many diseases, and have attracted the increasing attention of researchers. However, at present, the realization of many advantages of micro/nanomotors in disease treatment in vivo is still in its infancy, because of the complexity and particularity of diseases in different parts of human body. In this Minireview, we first focus on the biosafety and functionality of micro/nanomotors as a biomedical treatment system. Then, we address the treatment difficulties of various diseases in vivo (such as ophthalmic disease, orthopedic disease, gastrointestinal disease, cardiovascular disease, and cancer), and then review the research progress of biomedical micro/nanomotors in the past 20 years, Finally, we propose the challenges in this field and possible future development directions.

Helically Intersected Conductive Network Design for Wearable Electronic Devices: From Theory to Application

Flexible and stretchable strain sensors are crucial components for wearable electronics that can detect and quantify the stimuli from the environment and thus realize the rapid feedback and control of smart devices. However, reconciliation of the conflict between resourceful design of conductive networks and large-scale production in the industry still faces a huge challenge. Herein, we present a new flow-manipulated strategy to prepare a wearable strain sensor featuring a helically intersected conductive network, which exhibited easy integration, multidimensional sensibility, and robust mechanical properties. From visualization of simulation and verification of experimental results, the helically intersected conductive network formed in an elastomer ring can simultaneously reflect the static and dynamic mechanical responses with a tunable gauge factor (10.41-31.12), wide linear region (0-40^o), mechanical robustness (σ_s = ∼7 MPa, ε = ∼1400%), and rapid response time (∼300 ms). We further constructed a control system based on smart rings and demonstrated its application in controlling industrial robotic arms and remote-controlled cars. Looking ahead, this kind of a smart ring will be more widely used in space and underwater exploration, intelligent robotics, and human-machine interface technologies.

Towards Performant Design of Carbon-Based Nanomotors for Hydrogen Separation through Molecular Dynamics Simulations

Clean energy technologies represent a hot topic for research communities worldwide. Hydrogen fuel, a prized alternative to fossil fuels, displays weaknesses such as the poisoning by impurities of the precious metal catalyst which controls the reaction involved in its production. Thus, separating H₂ out of the other gases, meaning CH₄, CO, CO₂, N₂, and H₂O is essential. We present a rotating partially double-walled carbon nanotube membrane design for hydrogen separation and evaluate its performance using molecular dynamics simulations by imposing three discrete angular velocities. We provide a nano-perspective of the gas behaviors inside the membrane and extract key insights from the filtration process, pore placement, flux, and permeance of the membrane. We display a very high selectivity case (ω = 180° ps⁻¹) and show that the outcome of Molecular Dynamics (MD) simulations can be both intuitive and counter-intuitive when increasing the ω parameter (ω = 270° ps⁻¹; ω = 360° ps⁻¹). Thus, in the highly selective, ω = 180° ps⁻¹, only H₂ molecules and 1–2 H₂O molecules pass into the filtrate area. In the ω = 270° ps⁻¹, H₂, CO, CH₄, N₂, and H₂O molecules were observed to pass, while, perhaps counter-intuitively, in the third case, with the highest imposed angular velocity of 360° ps⁻¹ only CH₄ and H₂ molecules were able to pass through the pores leading to the filtrate area.

Micro/Nanorobot: A Promising Targeted Drug Delivery System

Micro/nanorobot, as a research field, has attracted interest in recent years. It has great potential in medical treatment, as it can be applied in targeted drug delivery, surgical operation, disease diagnosis, etc. Differently from traditional drug delivery, which relies on blood circulation to reach the target, the designed micro/nanorobots can move autonomously, which makes it possible to deliver drugs to the hard-to-reach areas. Micro/nanorobots were driven by exogenous power (magnetic fields, light energy, acoustic fields, electric fields, etc.) or endogenous power (chemical reaction energy). Cell-based micro/nanorobots and DNA origami without autonomous movement ability were also introduced in this article. Although micro/nanorobots have excellent prospects, the current research is mainly based on in vitro experiments; in vivo research is still in its infancy. Further biological experiments are required to verify in vivo drug delivery effects of micro/nanorobots. This paper mainly discusses the research status, challenges, and future development of micro/nanorobots.

Micro-/Nanomotors toward Biomedical Applications: The Recent Progress in Biocompatibility

Inspired by the highly versatile natural motors, artificial micro-/nanomotors that can convert surrounding energies into mechanical motion and accomplish multiple tasks are devised. In the past few years, micro-/nanomotors have demonstrated significant potential in biomedicine. However, the practical biomedical applications of these small-scale devices are still at an infant stage. For successful bench-to-bed translation, biocompatibility of micro-/nanomotor systems is the central issue to be considered. Herein, the recent progress in micro-/nanomotors in biocompatibility is reviewed, with a special focus on their biomedical applications. Through close collaboration between researches in the nanoengineering, material chemistry, and biomedical fields, it is expected that a promising real-world application platform based on micro-/nanomotors will emerge in the near future.

[Application of self-propelled micro-/nanomotors in active targeted drug delivery]

As a new type of micro-/nanomachines, self-propelled micro-/nanomotors (MNMs) can convert chemical or external energies from the surrounding environment into mechanical forces to produce autonomous motion. The ability of autonomous movement allows these MNMs to move actively to the targeted locations, and thus confers great potentials on the MNMs for applications in biomedicine, especially in drug delivery. MNMs have been shown to effectively load therapeutic payloads for active delivery to the disease site, which greatly improves the therapeutic efficacy and reduces side effects compared with the traditional nanodrugs. In this review, we provide an overview of different propulsion mechanisms of MNMs, including chemical propulsion based on redox reaction and external field propulsion driven by external energy such as light, magnetic field, electric field and ultrasound, followed by a review of the recent progress in active drug delivery based on MNMs in the past decade. We also discuss the current challenges and future perspectives of the application of the MNMs.

Magnetically Powered Annelid-Worm-Like Microswimmers

A bioinspired magnetically powered microswimmer is designed and experimentally demonstrated by mimicking the morphology of annelid worms. The structural parameters of the microswimmer, such as the surface wrinkling, can be controlled by applying prestrain on substrate for the precise fabrication and consistent performance of the microswimmers. The resulting annelid-worm-like microswimmers display efficient propulsion under an oscillating magnetic field, reaching a peak speed of ≈100 µm s^-1 . The speed and directionality of the microswimmer can be readily controlled by changing the parameters of the field inputs. Additionally, it is demonstrated that the microswimmers are able to transport microparticles toward a predefined destination, although the translation velocity is inevitably reduced due to the additional hydrodynamic resistance of the microparticles. These annelid-worm-like microswimmers have excellent mobility, good maneuverability, and strong transport capacity, and they hold considerable promise for diverse biomedical, chemical sensing, and environmental applications.