Digital biological fabrication
Turning to the exponential growth and parallelization capacity in biology, we are excited by the potential that biological materials offer for printing. The common Escherichia coli cell can replicate itself, along with all its internal complexity and high resolution, in approximately 20 minutes (genetically engineered strains of E. coli can approach doubling times much faster, currently down to 11 minutes). The concept of parallelization, in which individual fabrication units fabricate larger systems, is a powerful technique that biology applies to enable speed, robustness, adaption, and responsiveness. Applying the scaling laws, it is easy to imagine the vast potential for biological growth systems to be combined with digital controls and materials. In our work, we are exploring parallelization through large-scale fabrication with biological growth systems and digital controls.
Beginning in 2012, our group started studying silkworms, organisms that produce silk cocoons used for the world’s silk supply. Viewing the silkworms (Bombyx mori) in a framework akin to miniature 3D multimaterial 3D printers, scaffolding template experiments were conducted by the team led by Dr. Neri Oxman.[—] These experiments revealed silkworm motion patterns and provided scaffolding guidelines to produce flat sheets of silk as opposed to cocoons (the silkworms still metamorphose outside the silk into moths; the cocoon is for protection from predators). Using this data, a digital controls model was developed and a robotically constructed scaffold was produced to provide spatial information to the silkworms. 6,500 silkworms were placed on the scaffold and over the course of two weeks the silkworms layered the scaffold with silk in the geometry constructed by the digital controls model. When the scaffold was removed, the final Silk Pavilion was exhibited in the MIT Media Lab lobby, as shown in Figure 18-13. The Silk Pavilion, with its massive parallelization of additive fabrication, serves as an excellent example of the power-scaling potential for biology. By extension, looking around a common room and noticing the bulk of natural materials (for example, wood, cotton, and food), the potential for controlling biological growth models is very exciting.
Although existing biological organisms are impressive in their capacity to engage spatial and temporal growth and material variation, we are also intrigued by the potential to design biology itself through synthetic biology methods. These methods focus on genetic engineering through designing the gene pathways with logic structures analogous to electrical and computer engineering. Using the biological equivalents (using transcription factors) of logic gates (such as AND, NOT, and OR gates), genetic circuits can be designed and constructed within organisms.
Figure 18-13. Scanning electron microscopy images detail a typical silk cocoon, and the observed spinning patterns are highlighted in false color generated by surface orientation (top); the Silk Pavilion on display in the MIT Media Lab (bottom) (photo: Dr. James Weaver [top], Steven Keating [bottom])
In the future, what would wood look like if it were optimized for structure, color, homogeneity, speed of growth, and so on? Could we have living products? Cell phones that are half-biological and half-digital? Houses that can replicate or materials sourced from the air like plants? The new field of synthetic biology designs genetic biological functions for engineering solutions. Synthetic biology is an exciting area with serious potential to revolutionize not only medicine, but also fabrication and computation. The thoughts seem infinite, although we are just at the beginning of the science, tools, and capabilities to design basic synthetic biological systems.
The beginning building blocks of synthetic biology are emerging, as new science from the last decade has created designs for genetic circuits akin to logic gates. These genetic circuits are designed gene pathways made from materials such as deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) that program certain chemical actions from cellular organisms. From these basic logic gates, the goals of genetic circuits and computation are starting to emerge in scientific research by leading biologists in the field. As a research group, we are just in the first stages of getting our feet wet in the area, but we are enthused and look forward to a future of growth, temporal responsiveness, and hybrid systems with digital components.
Current research in our group in the area focuses on fabrication systems and mechanical means of combining top-down digital controls and bottom-up biological growth. Early work has generated inkjet distribution heads for printing cells, genetically modified cell lines for tunable biofilm growth, and mathematical models for using light to trigger fabrication gene pathways in cell lines for potential 3D printing techniques (see Figure 18- 14). in the future, we believe 3D printers will function with biological resins capable of complex parallelized growth with responsive temporal and spatial properties.
Figure 18-14. Genetically engineered Escherichia coli cells with a fluorescent tag (top); a biological print head using inkjet nozzles to print living cells onto substrates (bottom)
While these are very early predictions, we look forward to the future of printing living materials and believe that the capabilities in all of the dimensions discussed in this chapter — spatial, material, and temporal — hold the future for vast scaling potential, material/energy sourcing, and responsive products, as illustrated in Figure 18-15.
Figure 18-15. An overview chart detailing the spatial and temporal variations possible with different materials
systems (work in collaboration with Will Patrick)