We have developed two technologies for 3D magnetic microstructures, with a wide size range between 5μm to 2mm. The first technology enables us to obtain density controlled 3D magnetic microstructures. The size of this structure is approximately 500μm. In this scale, controlling density is vital for magnetic micro actuators, because the effect of gravity is strong. To adjust density, we developed the world's first “density controllable magnetically photocurable (DMPC) polymer.” The DMPC polymer is a mixture of hollow microcapsules (density, 0.03 g/cm3), magnetic particles, and photocurable polymer. We can obtain desired relative density between 0.5 to 1.7 by adjusting the concentration of microcapsules. In addition, we succeeded in 3D velocity control of a screw-type magnetic micro actuator with neutral buoyancy in water. The delay time was 32msec, which is smaller than video rate. In addition, the actuator possessed 6 degrees of freedom. The second technology realized a 5μm magnetic micro actuator, which is a combination of a 3D transparent structure and 2D magnetic structure. Various photocurable polymers can be applied as the 2D structure in this process, although we used magnetically photocurable polymer in this report. Furthermore, we have succeeded in driving a ferromagnetic micro actuator, whose diameter is as small as 1μm. These two fabrication processes will become key technologies in both the medical field and the field of life sciences, because they can supply a wide variety of 3D micro structures with small effort.

The world's smallest micro active catheter of φ∼300µm was successfully fabricated using membrane micro emboss following excimer laser ablation (MeME-X) process. The catheter has a one-sided hollow bellows at the tip made of thin polymer membrane. The bellows is composed of a series of folded micro-chambers and microchannels connecting the micro-chambers. The folded-chambers expand on one side by increasing inner water pressure using a syringe, thus the whole bellows bends toward one direction within 0 to 180 degree. This micro active catheter should be useful for safe intravascular surgery in narrow and complicated blood vessels. Moreover, the nonelectrical actuation mechanism of this catheter can be widely applied to micro-actuators and micro-robots which need high safety.