3D Printing coral-inspired structures

Materials World magazine
3 Jun 2020

Bionic 3D printed corals that can help produce energy and save coral reefs. 

Coral-inspired structures are being 3D printed from biocompatible polymer gels and hydrogels, doped with cellulose nanomaterials. The aim is to improve understanding of coral reefs by incubating algae growth, which produces energy, and mimicking the optical properties of living corals to reduce emissions responsible for reef deaths. 

Researchers from the University of Cambridge, UK, and University of California San Diego (UC San Diego), USA, claim their structures can grow 100 times faster than in standard liquid growth mediums. They are created using a rapid 3D bioprinting technique that can reproduce intricate structures mimicking complex living tissues. According to the team, this technique prints structures with micrometre-scale resolution in minutes – critical for replicating structures with live cells. 

‘In this project, we applied a multidisciplinary framework that integrates concepts of aquatic microbial ecology and optics into the design of biologically inspired bioenergy generation,’ says Dr Silvia Vignolini at the University of Cambridge. 

‘Specifically, we aimed to develop novel, coral-inspired, microalgal cultivation techniques for more efficient microalgal growth. At the same time, we started to develop a coral-algal symbiosis model system that allows us to create in vivo like conditions, crucial for understanding causes of coral death, such as coral bleaching.’ 

Looking to mimic the symbiotic relationship between corals and algae, the team has developed the structures so that they can assimilate natural coral’s high efficiency for collecting and using light. ‘3D printing allowed us to recreate structures with high spatial resolution, while at the same time giving us the flexibility to functionalise the polymers for on-demand control of optics, mechanics and cell viability,’ Vignolini explains. 

‘Cellulose is an abundant biopolymer – it is excellent at scattering light and we used it to optimise delivery of light into photosynthetic algae,’ she says. The results show that, just like natural corals, the structures are highly efficient at redistributing light. 

 The team used an optical analogue as an ultrasound, called Optical Coherence Tomography, to scan living corals and use the models for creating 3D printed designs. The 3D bioprinter is custom made, projecting blue light onto a digital micromirror device, which is controlled by a digital mask. This allows the projection of light by focusing optics onto the prepolymer solution, with a motor controlling the projected focus area and allowing for rapid development of the 3D structures in seconds. The printed coral copies natural coral structures and light-harvesting properties, creating an artificial host-microenvironment for the living microalgae.
The team now plans to scale the system for algal biotechnology. 

‘We are also working on further fine-tuning the mimicry of the coral-algal symbiosis, thus creating synthetic symbiotic systems,’ says Vignolini. ‘This is very important for understanding corals and the demise of coral reefs worldwide.’