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Mechanically programmable, reconfigurable micro/nanoscale materials that can dynamically change their mechanical properties or behaviors, or morph into distinct assemblies or swarms in response to stimuli have greatly piqued the interest of the science community due to their unprecedented potentials in both fundamental research and technological applications. To date, a variety of designs of hard and soft materials, as well as actuation schemes based on mechanisms including chemical reactions and magnetic, acoustic, optical, and electric stimuli, have been reported. Herein, state‐of‐the‐art micro/nanostructures and operation schemes for multimodal reconfigurable micro/nanomachines and swarms, as well as potential new materials and working principles, challenges, and future perspectives are discussed.

 

To develop active materials that can efficiently respond to external stimuli with designed mechanical motions is a major obstacle that have hindered the realization nanomachines and nanorobots. Here, we present our finding and investigation of an original working mechanism that allows multifold reconfigurable motion control in both rotation and alignment of semiconductor micromotors in an AC electric field with simple visible-light stimulation. In our previous work, we reported the instantly switchable electrorotation owing to the optically tunable imaginary part of electric polarization of a semiconductor nanowire in aqueous suspension[1]. Here we provide further experimental confirmation along with numerical simulation. Moreover, according to the Kramers-Kronig relation, the real part of the electric polarization should also be optically tunable, which can be experimentally verified with tests of electro-alignment of a nanowire. Here, we report our experimental study of light effect on electro-alignment along with theoretical simulation to complete the investigation of opto-tunable electric polarization of a semiconductor nanowire. Finally, we demonstrate a micromotor with periodically oscillating rotation with simple asymmetric exposure to a light pattern. This research could inspire development of a new class of micro/nanomachines with agile and spatially defined maneuverability. 

2D transition‐metal‐dichalcogenide materials, such as molybdenum disulfide (MoS₂) have received immense interest owing to their remarkable structure‐endowed electronic, catalytic, and mechanical properties for applications in optoelectronics, energy storage, and wearable devices. However, 2D materials have been rarely explored in the field of micro/nanomachines, motors, and robots. Here, MoS₂ with anatase TiO₂ is successfully integrated into an original one‐side‐open hollow micromachine, which demonstrates increased light absorption of TiO₂‐based micromachines to the visible region and the first observed motion acceleration in response to ionic media. Both experimentation and theoretical analysis suggest the unique type‐II bandgap alignment of MoS₂/TiO₂ heterojunction that accounts for the observed unique locomotion owing to a competing propulsion mechanism. Furthermore, by leveraging the chemical properties of MoS₂/TiO₂, the micromachines achieve sunlight‐powered water disinfection with 99.999% Escherichia coli lysed in an hour. This research suggests abundant opportunities offered by 2D materials in the creation of a new class of micro/nanomachines and robots.

 

The performances of porous graphitic foams in flexible electronic, electrochemical, and thermal management devices can be enhanced by increasing the interfacial charge or heat transport between the 3D graphitic network and the functional materials filled into the pore space. Herein, an investigation of the effects of chemical vapor deposition (CVD) conditions on the structure and thermal conductivities of both graphitic foams grown from reticular Ni foams and dendritic graphitic foams (DGFs) synthesized from electrodeposited dendritic Ni foams is reported. A room‐temperature solid thermal conductivity () up to 800 W m⁻¹ K⁻¹is obtained from the graphitic foams (GF) with less than 1% volume fraction. In comparison, the DGFs, which provide a large increase of the specific surface area for enhanced interfacial heat transfer, achieve an effective thermal conductivity of 2.5 ± 0.2 W m⁻¹ K⁻¹because of an enhanced volume fraction to about 5% despite a compromised around 200 W m⁻¹K⁻¹due to the increased defect density. Through systematical variations of the catalyst template morphology and CVD conditions, this work reveals the distinct roles of catalyst surface curvature and graphitic strut thickness in controlling the properties of GFs and DGFs for thermal management.

 

In this review, we focus on engineered nanomaterials (NMs) offering economic and environmental sustainability in oil extraction. We introduce underlying issues in oil recovery and separation and discuss fundamental physical and chemical interactions in typical oil‐water‐solid systems that guide the design of NMs. In recovery, the NMs change rock wettability, permeability, or sweep fluid properties to attain optimal resource use and minimal environmental impact. Applied NMs include nanosurfactants, silica core‐shell structures, nano‐encapsulated acids, and nanofluids. While for separation, the NMs use mechanisms of adsorption, filtration, or dispersion to improve separation performance in industrial or aquatic oil spill settings. The NMs include iron oxide nanoparticles, graphene Joule‐heating sponges, superhydrophilic poly(vinylidene fluoride) membranes, and amphiphilic Janus silicon dioxide nanoparticles. Albeit the NMs exhibit impressive performance in sustainable oil extraction, a technological gap remains between the lab‐scale demonstrations and practical field deployment. We conclude with a perspective on bridging this gap.

 

Subwavelength optical resonators with spatiotemporal control of light are essential to the miniaturization of optical devices. In this work, chemically synthesized transition metal dichalcogenide (TMDC) nanowires are exploited as a new type of dielectric nanoresonators to simultaneously support pronounced excitonic and Mie resonances. Strong light–matter couplings and tunable exciton polaritons in individual nanowires are demonstrated. In addition, the excitonic responses can be reversibly modulated with excellent reproducibility, offering the potential for developing tunable optical nanodevices. Being in the mobile colloidal state with highly tunable optical properties, the TMDC nanoresonators will find promising applications in integrated active optical devices, including all‐optical switches and sensors.