A technique was developed that uses a specially adapted 3D printer to build therapeutic biomaterials from multiple materials. The advance could be a step toward on-demand printing of complex artificial tissues for use in transplants and other surgeries.
The technique uses a light-based process called stereolithography, and takes advantage of a customized 3D printer design that has two key components. The first is a custom-built microfluidic chip — a small, flat platform similar in size to a computer chip — with multiple inlets that each “prints” a different material. The other component is a digital micromirror, an array of more than a million tiny mirrors that each moves independently.
Different types of hydrogels — materials that, after passing through the printer, form scaffolds for tissue to grow into — were used.
The micromirrors direct light onto the printing surface, and the illuminated areas indicate the outline of the 3D object being printed. The light also triggers molecular bonds to form in the materials, which causes the gels to firm into solid material. As the 3D object is printed, the mirror array changes the light pattern to indicate the shape of each new layer.
The process is the first to use multiple materials for automated stereolithographic bioprinting — an advance over conventional stereolithographic bioprinting, which only uses one type of material. While the demonstration device used four types of bio-inks, the process could accommodate as many inks as needed.
The process was first used to make simple shapes such as pyramids. Then, complex 3D structures were made that mimicked parts of muscle tissue and muscle-skeleton connective tissues. Shapes mimicking tumors also were made with networks of blood vessels that could be used as biological models to study cancers.