Discovery of bio-inspired, self-propelled and externally-powered nano-/micro-motors, rotors and engines (micromachines) is considered a potentially revolutionary paradigm in nanoscience. Nature knows how to combine different elements together in a fluidic state for intelligent design of nano-/micro-machines, which operate by pumping, stirring, and diffusion of their internal components. Taking inspirations from nature, scientists endeavor to develop the best materials, geometries, and conditions for self-propelled motion, and to better understand their mechanisms of motion and interactions. Today, microfluidic technology offers considerable advantages for the next generation of biomimetic particles, droplets and capsules. This review summarizes recent achievements in the field of nano-/micromotors, and methods of their external control and collective behaviors, which may stimulate new ideas for a broad range of applications.

Bismuth ferrite BiFeO₃ (BFO)-based ferroelectrics have great potential as inorganic perovskite-like oxides for future solar cells applications due to their unique physical properties. In this work, La and Mn co-doped BFO thin films with compositions Bi_0.9La_0.1(Fe_1−xMn_x)O₃ (x = 0, 0.05, 0.1, 0.15) (denoted as BLF, BLFM5, BLFM10, BLFM15, respectively) were prepared via a sol–gel technique on indium tin oxide (ITO) glass. All the films are monophasic, showing good crystallinity. The optical bandgap E_g was found to decrease monotonously with an increase in the Mn doping amount. Compared with other compositions, the BLFM5 sample exhibits a better crystallinity and less oxygen vacancies as indicated by XRD and XPS measurements, thereby achieving a better J–V performance. Based on BLFM5 as the light absorbing layer, the ITO/ZnO/BLFM5/Pt and ITO/ZnO/BLFM5/NiO/Pt heterostructure devices were designed and characterized. It was found that the introduction of the ZnO layer increases both the open circuit voltage (V_oc) and the short circuit current density (J_sc) with V_oc = 90.2 mV and J_sc = 6.90 μA/cm² for the Pt/ BLFM5/ZnO/ITO device. However, the insertion of the NiO layer reduces both V_oc and J_sc, which is attributed to the weakened built-in electric field at the NiO/BLFM5 interface.

The wide optical band gaps of ferroelectric perovskite oxides have restricted their light absorbing capacities in the photovoltaic devices. In this work, an ultra-narrow band gap E _g and wide optical absorption across the ultraviolet-visible-infrared sunlight spectrum was achieved in lanthanum and strontium atoms modified Bi(Fe, Mn)O₃ perovskites by chemical substitution and defect engineering. XRD results show that the A and B site co-substituted samples are single phase. The XPS characterizations indicate the Fe ions are in the trivalent state for all the samples. The LM6 and SM6 samples exhibit an ultra-narrow band gap about 1.26 eV and 1.06 eV, respectively. The reduced E _g was due to the defect states produced within the band gap, acting as a scaffold to give electrons to Fe 3d states and receive the electrons from O 2p states. Based on this research, these chemically modified BFO based perovskite could potentially extend its sunlight absorption deep into the infrared region.

Different levels of isovalent dopant vanadium were doped on the B site of Sr₂Nb₂O₇ to explore the doping effect on its dielectric and ferroelectric properties. A second phase could be detected with above 1 mol% V₂O₅ doping. The grains after doping remained anisotropic and plate-like. The samples are not dense, as there are pores present at the grain boundaries. The corrected dielectric constant for 0.1 mol%, 0.2 mol%, and 0.3 mol% V doped SNO at 1 MHz is around 46, 48 and 49, respectively, which indicates the effect of V doping on the increase of dielectric constant of SNO (ε_r is about 40 at 1 MHz). The Curie point T_c increased with the increase in the V doping level. The relatively high d₃₃ (2.3 pC/N) measured from the non-dense and untextured samples indicates the potential effect of V₂O₅ doping on the improvement of piezoelectricity of SNO.