## 3 Manipulation of Micro Actuator
### Magnetically Manipulated Micro-Actuator/Robot
To impart magnetic properties to a limited region, an Ni/Ti bimetallic layer can be coated only onto a desired region using a sacrificial mask. [PERSON] et al. fabricated a cilia-inspired micro-robot in which only the cilia parts were coated with an Ni/Ti bilayer, with the other parts remaining uncoated via the use of a sacrificial mask that blocked the coating and was removed after the end of the coating process [63] (Figure 2e-h). By mimicking a _Paramecium_, the cilia parts are actuated using non-reciprocal motion by applying an external magnetic field and generating a net propulsive force that enables the precise actuation of a cilia-inspired microactuator. Considering the strength of TPP, the fabrication of complex functional microstructures with functions other than actuation by magnetic field is possible. There is no need for an additional assembly process to bond functional and actuation parts when using TPP and selective magnetic deposition for the targeted and triggered delivery of materials. A syringe-shaped micro-transporter was devised for the efficient delivery of drugs and therapeutic agents via a corkscrew motion [72]. This transporter is different from other actuators in that various tasks such as the loading, releasing, and transporting of agents can be achieved. A pumping mechanism based on Archimedes screw-pump was designed to load and unload materials according to capacity. Other passive and active suspensions could be transported inside a selective microfluidic system using this method. If this unique structure is used for bio-related applications, it is expected that it will be possible to reach a specific remote region (e.g., gastrointestinal tract) and deliver drugs to said target. It also able to perform more complicated tasks such as occlusions removal, the sampling of cells or tissues for diagnostic analysis, and local fluid flow generation for mixing. A micro-rotor that used Pd for catalyst absorption and Fe\({}_{3}\)O\({}_{4}\) for deposition was utilized to treat acrylic-based structures was proposed [69] (Figure 2i,j). By grafting different types of materials, the fabrication of hybrid microactuators that can be driven by magnetic force and equipped with functionality can be achieved. A hybrid artificial bacterial flagellum (h-ABF) consisting of a ferromagnetic alloy head and a spiral polymer tail was fabricated,and it was found to have many advantages over all-metal structures. Because an h-ABF replaces metal parts with polypyrrole (PPy), it is lightweight and sedimentation reduction, navigation enhancement, and biocompatibility improvements [73]. A 3D cavity part can be filled with magnetic cobalt/nickel (Co/Ni) and biocompatible PPy by electrodeposition. An h-ABF is physically stable in an aqueous environment with a rigid connection between the metallic and polymeric segments. Swarm control can be performed by the wireless manipulation of the h-ABF with a rotating magnetic field. A capsule-type micro-robot consisting of a cap and a plunger was fabricated to deliver drugs or cells to a targeted region [3]. Only the plunger part was magnetic, and it was confirmed that actuation was possible under an external magnetic field. Drugs or cells can be encapsulated in a container before being transported to a target location in vitro via corkscrewing and \"pick-and-drop\" (P and D) motions. Porous-shaped actuators with bigger capacities and porous niche-shaped structures have also been proposed. Cylindrical and hexahedral-shaped 3D micro-niche actuators were fabricated and then coated with Ni/Ti bilayers for the culture and transportation of cells to a targeted position under magnetic field gradients [65]. The cylindrical-shaped micromachine showed a higher moving speed compared to that of the hexahedral-shaped actuator. As a biocompatible magnetic-driven actuator, hydrogel-based biodegradable micro-swimmers have been fabricated by TPP [74]. This structure can facilitate promising biomedical applications in fields such as biology, medicine, drug delivery, and diagnostics.