Precise and low-cost submicron fabrication technique for manufacturing human spare parts

VTT Technical Research Centre of Finland, Tampere University of Technology and Nanofoot Finland Oy have developed a direct-write three-dimensional forming method for biomaterials. The methodology enables the fabrication of nano and micrometer scale structures that can be used as parts of tissue engineering scaffolds. The project is being funded by the BioneXt Tampere Research Programme.

The new process is based on the use of visible light, ultra short pulse laser. When focused inside photopolymerizable material, the radiation causes a reaction in which two photons are absorbed simultaneously, thus leading to the polymerization of the material. One of the advantages of this process, known as the two-photon polymerization process, is that the fabrication occurs below the surface of liquid material and the polymerization is confined to the point of focus whose diameter can be much less than 1 micrometer. The conventional ultraviolet light-induced polymerization causes hardening of the material along the entire path of the UV beam, making it impossible to form very small three-dimensional features. The two-photon polymerization process requires no utilization of special photolithographic masks since the structure is formed inside the liquid volume.

High-accuracy biomaterial structures need to be used as tissue engineering scaffolds or cell culture platforms where the fine features have to follow the dimensions of the cultured cells. So far, the smallest features achieved in this project have been about 700 nanometers wide. As a reference, one can compare it to the epithelial cells, which have a diameter of 11000 - 12000 nm, or viruses that range in size between 10 - 100 nm. The fabricated structures can be made of biodegradable materials and are biocompatible. The process can also be utilized in manufacturing structures for other applications, e.g. optical waveguides, photonic crystals, and microfluidic channels.

Another advantage of this process is the possibility to utilize an inexpensive, low-power laser. Other research groups have typically used very expensive femtosecond titanium-sapphire pulse lasers. A much cheaper laser that produces longer, picoseconds-width pulses has been used in the project. As far as is known, there is only one research group in the USA that has previously succeeded in polymerizing biomaterials with a similar system.

The project has been accomplished as an interdisciplinary collaboration. Research Scientist Sanna Peltola from the Institute of Biomaterials, Tampere University of Technology has been responsible for the development of materials, and the research group of Research Professor Jouko Viitanen from VTT has developed the laser system. The stem cell culturing requirements have been specified by the researchers of the Tampere University. Nanofoot Finland Oy is commercializing the new process. The company offers versatile services in the area of laser machining.

 


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