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Purpose of Review The increasing number of contributions in the field of small-scale robotics is significantly associated with the progress in material science and process engineering during the last half century. With the objective of integrating the most optimal materials for the propulsion of these motile micro- and nanosystems, several manufacturing strategies have been adopted or specifically developed. This brief review covers some recent advances in materials and fabrication of small-scale robots with a focus on the materials serving as components for their motion and actuation. Recent Findings Integration of a wealth of materials is now possible in several micro- and nanorobotic designs owing to the advances in micro- and nanofabrication and chemical synthesis. Regarding light-driven swimmers, novel photocatalytic materials and deformable liquid crystal elastomers have been recently reported. Acoustic swimmers are also gaining attention, with several prominent examples of acoustic bubble-based 3D swimmers being recently reported. Magnetic micro- and nanorobots are increasingly investigated for their prospective use in biomedical applications. The adoption of different materials and novel fabrication strategies based on 3D printing, template-assisted electrodeposition, or electrospinning is briefly discussed. Summary A brief review on fabrication and powering of small-scale robotics is presented. First, a concise introduction to the world of small-scale robotics and their propulsion by means of magnetic fields, ultrasound, and light is provided. Recent examples of materials and fabrication methodologies for the realization of these devices follow thereafter.

Porphyrins and phthalocyanines are widely studied molecules for various functional applications. Researchers have investigated these photoactive compounds for electrochemical, sensor, semiconductor and photodynamic therapy purposes. Layer-by-layer (LbL) self-assembly is preferred for its simple, environmentally-friendly and water-based features compared to other coating techniques in the literature. Coating thickness can be controlled on the order of nanometers by LbL mechanism. Multilayer thin film formation of diverse phthalocyanine-based molecules is examined in terms of molecular orientation and temperature dependency by the LbL method. However, as well as concentration and temperature, the pH of the coating medium is another challenging parameter in the LbL approach. Film thickness and layer distribution are influenced by pH value, changing ionic density and hence the strength of electrostatic interactions during LbL assembly. In this study, layer-by-layer deposition of branched poly(ethyleneimine)/nickel(II)phthalocyanine-tetrasulfonic acid tetrasodium salt (NiPcTS) coating pair is studied. Impact of pH and concentration of NiPcTS on thin film properties are tested for four different pH conditions. Corresponding analysis is made by UV-vis spectroscopy, surface profiler and quartz-crystal microbalance. LbL deposition of NiPcTS is homogeneously controlled and 98 nm thick films are obtained in the presence of acidic media.

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