Updated: Nov 18, 2020
Touted as the next industrial revolution,3D-printing reduces manufacturing costs of creating prototypes, parts, and tools. Just as the world is settling into the idea of additive manufacturing for industrial applications, the next revolution in 3D printing, a new method based on 3D-light patterning, is quickly moving from laboratory research into applications ranging from metal sintering and as our company is adapting the technology: regenerative medicine.
3D-Printing 1.0: Democratization of Manufacturing
Democratization of complex manufacturing was enabled by the first wave of 3D-printing technology. For a relatively inexpensive price point and a few CAD files exchanged online, anyone could re-create parts overnight with a table-top printer.
Table-top printers also increased the speed that ultra-complex, reasonably high-resolution structures could be created. This drove down the price while increasing the speed of innovation, allowing rapid low-cost iterations of ideas.
From 3D printed houses to micrometer-precise parts, instead of warehouses of tools, only one machine was needed to create these structures: the extrusion printer. Fed the correct design files an extrusion printer, with a large (house) or small (fine parts) nozzle would automatically deposit your building material of choice in a set pattern. Need a house? Set it up, add concrete, come back 24 hours later and start to move in your furniture.
Extrusion printing is a great way to build with additive manufacturing, and has been applied in many branches of research, however in many it falls short of being an all-encompassing technology. One important example is with metal-based 3D printing where molten metal doesn’t lend itself well to incremental layering. Another critical example is in regenerative medicine, specifically human organ and tissue engineering. To print a human organ, the near impossible triad of speed, extremely high resolution, and large print areas must be simultaneously addressed to build a functional tissue.
Speed is necessary because cells have a shelf-life and can die off in a matter of hours. Resolution of the printer must be at sub-micrometer scales, allowing for the fine tissue structures our cells call home to be created. Resolution alone, however, is not enough, the printing must be highly precise. Precision is critical because of the heterogeneity of tissues wherein tiny blood vessels must be spaced correctly between multi-cellular niches poses another technical challenge.
Extrusion printing does not solve any of these problems, leaving human tissue printing stalled at the heavy paper-width print thickness. Go thicker? Cells begin to die because oxygen and nutrients can not access the center of the structure without the necessary tiny blood vessels, microvascualture.
3D-Printing 2.0: Light Patterning Revolution
So, what is ultra-fast, can produce super-high resolution paterns, and can cover a large area?
Light-based polymerization of materials is not a new concept. UV-cured plastics, epoxy resins, and gel-based manicures are examples of light-curing materials we encounter in our daily lives.
But how do we apply this concept to human organ and tissue engineering? Lasers (or light if you will) can cause a similar reaction in proteins and cell-safe non-toxic polymers. By creating a pattern with light, rapid production of high resolution structures can be projected in light-reactive materials, and this technique has been used for many years in chemistry and physics laboratories.
Laser-based scanning works but the technology is still too slow to create larger format tissues with the highly complex structures necessary for supporting the cells within them. This led to an attempt to add cells to 3D printed structures after the print was completed. However, cells live in heterogeneous layers and form niches of specific cell types, complicating how layers and complex groupings of cells necessary to create an organ could be correctly layered in three dimensions.
Light, however, has some interesting properties that when extrapolated by physical means can be used in manufacturing. Phase modulation of coherent light (lasers) can be used to generate 3D printed structures, with near-instantaneous speed.
With this Prellis Biologics, Inc is creating a 3D-printer capable of printing volumes that are cubic (made up of voxels), rather than flat 2D projection planes, or 1D raster-scanning of a pin-point laser which traces images pixel, by pixel.
Our current generation laser system projects several thousand voxels at the same time, distributed in the x,y, and z dimensions.
By printing cubic volumes the print speed is then limited only by the optics, speeding up printing time in relation to complexity exponentially, all while solving the issues of resolution versus speed in a time scale that allows for manufacturing that is compatible with cells.
Laser (or light) based 3D-printing is the next revolution in additive manufacturing highly applicable for human organ and tissue engineering that was previously limited by speed and resolution, or, if you will, time and space.