The development of a micromotor with unique spiky morphology based on sporopollenin exine capsules (SECs) is reported here. A widely abundant natural material extracted from sunflower pollen grains, the SECs are physically robust, highly monodisperse microcapsules that are ornamented with spiky appendages, opening the door to exploring bubble generation on this unique biomaterial surface. Partial platinum coating on the SEC surface enables catalytic decomposition of hydrogen peroxide that leads to bubblepropelled motion of individual SECs. Moreover, the hollow capsule architecture provides a large internal cavity for macromolecular encapsulation, as demonstrated here by the loading and transport of bovine serum albumin. Taking advantage of the sporopollenin biopolymer's capacity for heavy metal binding, it is further demonstrated that fluid mixing induced by the motion and bubble generation of the SEC micromotors dramatically improves heavy metal binding and removal. The bioinspired micromotors combine the advantageous properties of SECs with autonomous motion ability, resulting in a multifunctional platform for drug delivery and water purification applications.

Catalytic light‐powered micromotors have become a major focus in current autonomous self‐propelled micromotors research. The attractiveness of such machines stems from the fact that these motors are “fuel‐free,” with their motion modulated by light irradiation. In order to study how different metals affect the velocities of metal/TiO2 micromachines in the presence of UV irradiation in pure water, Pt/TiO2, Cu/TiO2, Fe/TiO2, Ag/TiO2, and Au/TiO2 Janus micromotors are prepared. The metals have different chemical potentials and catalytic effects toward water splitting reaction, with both the effects expected to alter the photoelectrochemically‐induced reaction and propulsion rates. Analysis of structures, elemental compositions, motion patterns, velocities, and overall performances of different metals (Pt, Au, Ag, Fe, Cu) on TiO2 are observed by scanning electron microscopy, energy dispersive X‐ray spectroscopy, and optical microscopy. Electrochemical Tafel analysis is performed for the different metal/TiO2 structures and it is concluded that the effective velocity is a result of the synergistic effect of chemical potential and catalysis. It is found that the Pt/TiO2 Janus micromotors exhibit the fastest motion compared to the rest of the prepared materials. Furthermore, after exposure to UV light, every fabricated micromotor shows high possibility of forming assembled chains which influence their velocity.

The production of large quantities of micromachines and microrobots is limited by fabrication methods and the use of synthetic templates. Pollen is one of the most stable structures in the world, capable of surviving harsh treatment and for millions of years. Pollen grains are available in large variety of shapes and sizes. The use of a wide variety of naturally abundant, nontoxic pollen grains for the efficient fabrication of platinum-pollen (Pt-pollen) hybrid microrobots capable of fast propulsion for environmental and biomedical applications is demonstrated. Nine different pollen grains are selected and modified (dandelion, pine, lotus, sunflower, poppy, camellia, lycopodium, cattail, and galla) to demonstrate the robustness of different types of pollen grains for potential applications in environmental remediation. The efficient mobility rendered by the fabricated microrobots enhances their performance in the removal of heavy metals in aqueous medium. Furthermore, they can be used as doxorubicin carriers.

Self-propelled, autonomous micro and nanomachines are at the forefront of current nanotechnology. These micro and nanodevices move actively to perform desired tasks, usually using chemical energy from their surrounding environment. Typically, these structures are fabricated via clean room or template-based electrodeposition methodologies, which yield relatively low numbers of these devices. To utilize these machines in industrial-scale operations, one would need an inexpensive fabrication route for mass production of nanomachines. The use of naturally occurring nanotubes, Halloysite nanoclay, to fabricate functional nanomotors in great quantities is demonstrated. These nanotubes can be mined in ton quantities and used as base for the fabrication of nanomachines. In addition, it is well known that the surface groups of Halloysite nanoclay bind strongly with heavy metals, which makes it potentially useful in environmental remediation. Figure 3. Influence of exposure time on the adsorption of heavy metals. A,B) Removal efficiency of Zn 2+ and Cd 2+ by "on-the-fly" Pt-Halloysite nanoclay nanomotors. Experimental conditions: heavy metal concentration 10 ppm, 0.5 mg mL −1 of Halloysite nanoclay, 4% H 2 O 2 , 1% SDS, 23 °C. www.afm-journal.de www.advancedsciencenews.com 1802762 (5 of 5)

Micromachines are at the forefront of materials research as they are self‐propelled, smart autonomous systems capable of acting as an intelligent matter. One of the obstacles the field faces is tracking individual micromachines carrying molecular cargo from the rest of the micromachines. Highly stable fluorescent markers based on chemically modified 2D germanene compounds are developed. Two different 2D germanene derivatives, 4‐fluorophenylgermanane (2D‐Ph‐Ge) and methylgermanane (2D‐Me‐Ge), exhibit different fluorescence under UV light irradiation (excitation at 365 nm), which allows one particular micromotor to be easily distinguished in a mixture of micromotors. This offers a paradigm shift toward a new approach of multiplex detection of self‐propelled micromachines. The utility is demonstrated on a drug delivery system, where micromachines carrying a drug are labeled with 2D‐Ph‐Ge with blue emission while bare micromachines are labeled by 2D‐Me‐Ge with red emission. This approach of functional fluorescent labeling will pave the way to multiple simultaneous functionalized micromachines identification in complex environments.