membrane micromachining
The microscale structures of living organisms in nature are made of membranes that are relatively thin compared to their characteristic size. This fundamental property makes life a highly adaptable system from a chemical and physical point of view. In addition, the small thickness of the membrane facilitates the transport of heat and substances between the living body and its surrounding environment, giving the living body flexibility and allowing passive and active morphological changes to adapt to the environment. make it possible.
These characteristics of biological microstructures should greatly support the development of new types of microdevices. In our laboratory, we are researching three-dimensional microfabrication technology for such biological membrane microdevices and its application to the biomedical field.
The main application of membrane-based microdevices is minimally invasive surgical tools. We have developed a pressure-driven microactive catheter and its fabrication process. This catheter was fabricated using the Membrane Micro Emboss Follow Eximer Laser Ablation (MeME-X) process.
This catheter has a single-sided hollow bellows made of a thin polymer film at its tip. The bellows consists of folded microchambers and microchannels that connect the microchambers. When the internal pressure is increased with a syringe, the folded microchamber expands to one side, causing the entire bellows to bend in one direction within the range of 0 to 180°. This micro-active catheter is expected to be useful for safe endovascular surgery in narrow and complex blood vessels. Additionally, the non-electrical actuation mechanism of this catheter can be widely applied to soft microrobots.
1.M. Ikeuchi and K. Ikuta, "Development of pressure-driven micro active catheter using membrane micro emboss following excimer laser ablation (MeME-X) process," 2009 IEEE International Conference on Robotics and Automation, 2009, pp. 4469-4472, doi: 10.1109/ROBOT.2009.5152869.
Microporous 3D printing by phase separation-assisted electrospray
In electrospinning, the viscosity of the polymer solution influences the morphology of the product. Reducing the viscosity of the polymer solution gradually atomizes the nanofibers and, at sufficiently low viscosity, forms fine particles (a process called electrospraying). We discovered nanomesh microcapsules, which are an intermediate form between nanofibers and microparticles, produced by electrospraying in a high-humidity environment [1].
Nanomesh microcapsules have characteristics of both nanofibers and microparticles. In other words, the surface of microcapsules is composed of nanofibers and can be treated as particles at the same time. Here, we introduce a new method using electrostatic lenses for focusing nanomesh microcapsules. By moving the target electrode, microcapsule formation and arbitrary shape patterning can be achieved in one step.
1.Electrospray deposition and direct patterning of polylactic acid nanofiber microcapsules for tissue engineering. Biomed Microdevices 14, 35-43 (2012). https://doi.org/10.1007/s10544-011-9583-x
Fabrication of microchannel using sacrificial molding
We have developed a new method to create microchannels inside a PDMS thin film by utilizing the moisture permeability of polydimethylsiloxane (PDMS).
In this method, first, caramel prepared by heating sugar is applied directly to the PDMS thin film using a micro nozzle. Next, the caramel encapsulated in PDMS is eluted with water vapor to create a microchannel.
Compared to the existing method, soft lithography, it does not require special equipment and the manufacturing process is simple and quick. Furthermore, it can also be applied to create microchannels with circular cross sections. Additionally, this method has excellent biocompatibility and can be applied to biotechnology and medical fields. Using this method, we were able to create circular cross-sectional straight channels with a minimum diameter of 1 μm, two-dimensional channels with a minimum width of 8 μm, and three-dimensional intersecting channels.
1.Y. Koyata, M. Ikeuchi and K. Ikuta, "Sealless 3-D microfluidic channel fabrication by sacrificial caramel template direct-patterning,"
2013 IEEE 26th International Conference on Micro Electro Mechanical Systems (MEMS),2013, pp. 311-314 , doi: 10.1109/MEMSYS.2013.6474240.