In this paper, a biomimetic microstructure related to cilia, which are effective fluidic and conveying systems in nature, is described. Authors have already reported that a magnetic elastomer pillar actuated by a rotating magnetic field can work like a natural cilium. In the present work, we show examples of a cilia array with a metachronal wave as the next step. A metachronal wave is a sequential action of a number of cilia. It is theoretically known that a metachronal wave gives a higher fluidic efficiency; however, there has been no report on a metachronal wave by artificial cilia. We prepared magnetic elastomer pillars that contain chainlike clusters of magnetic particles. The orientation of chains was set to be different in each pillar so that each pillar will deform with a different phase.

The authors have proposed a fabrication process of "4D printer" for magnetic soft actuators. In this paper, we applied this 4D printer to bio-mimic field and show some examples using a gel material dispersed with magnetic powder. 4D printer is a recently developed process that can print out not only a 3-dimensional structure but also print deformations of the printed structure at the same time. We employed a UV-curable gel material. The material could be used in the same manner as the conventional 3D-printing process. We applied a magnetic field to set magnetic anisotropy in the curing portion during the building step. This anisotropy is set in each portion of the structure so that the printed structures could deform under an applied magnetic field. Using this technique, we demonstrated 2 kinds of biomimetic examples; one is a worm-type soft actuator and the other is an array of artificial cilia. The first example could crawl in a narrow gap. The second one could reproduce a metachronal wave, which is a phase propagation wave found on natural small organisms. We will also show a computational method to design the deformation of the structure.

In this paper, we describe the development of magnetically actuated artificial cilia. Natural cilia are a highly efficient device that produces flow under a small-Reynolds-number state. There are two important characteristics of natural cilia; one is asymmetric movement, which is composed of effective and recovery strokes, and the other is the phase difference of a stroke in each cilium in an array that will produce a metachronal wave. In this paper, we propose an actuation system for artificial cilia composed of a silicone elastomer and multiparticle chains of a magnetic material. The applied magnetic field is controlled by rotation of a permanent magnet. This rotating magnetic field induced an asymmetric movement similar to that of a natural cilium. We also changed the orientation angle of multiparticle chains to control the phase difference of a stroke in each artificial cilium. This technique would help to realize metachronal waves of artificial cilia.

Artificial cilia actuated by an applied magnetic field have been developed. In our previous report, we demonstrated actuated cilia of a few millimeters scale, which were fabricated by cutting a magnetic elastomer sheet. The fabricated artificial cilia worked similarly to natural cilia; however, they had a much larger structure than natural ones, and showed difficulty for use in pumping systems in micro-total analysis systems (µTAS) fields. Thus, our goal is further miniaturization. In this study, we introduce a new process of fabricating smaller pillar structures with a magnetic orientation in each pillar by ultraviolet (UV) laser machining. We also give different orientations to groups of pillars by the alternate laser machining of the mold and casting processes.

In this paper, we developed a new 3D-printing system for magnetic elastomer, and demonstrated to fabricate artificial cilia. Natural cilia are hair-like organ found in nature. They are effective fluidic system in the natural world that are widely observed on surfaces of microorganisms of creatures, such as Paramecium and throat surface of mammals. Recently, the motion of cilia has been analyzed and mimicked for developing soft actuator, for example, some studies on artificial cilia driven magnetically have been reported. They are small soft actuators, and there are various manufacturing methods for these actuators depending on materials and products. Among them, authors have already developed the concept of a printing system that not only forms a three-dimensional object but also prints out the deformation of the structure. This system can fabricate various shapes of soft actuators without any assembly. In this report, we utilized UV-curable urethane acrylate as a more flexible material than that used in the previous reports, and fabricated artificial cilia by the printer. We set magnetic anisotropy to each cilium and mimicked a metachronal wave, sequential action of plural cilia that causes effective flow.