Nature has spent millions of years developing answers to problems. He has devised ingenious solutions to build strong structures, harvest energy, and produce iridescent colors. Scientists are increasingly turning to the natural world for inspiration to create new and greener materials and technologies.
In Silvia Vignolini’s lab at the University of Cambridge, UK, scientists are designing biodegradable glitter and natural dyes for food coloring and cosmetics as part of a project called PlaMatSu.
To do this, they use cellulose, a natural fiber that gives trees and plants strength and rigidity. It is what we make paper from. “It is the most abundant material we have on the planet,” says Vignolini. “Everyone thinks about its strength, but not everyone knows that cellulose can be used to make pigments.”
Pure cellulose is white like snow. To create colors, Vignolini carves small cellulose shapes from which light bounces off as bright colors, something called structural color.
“By structuring material at the nanoscale, light interacts with it in a way that creates color,” says Vignolini. We are more familiar with this phenomenon than we think: think of the nuances that soap bubbles create when bending light or the colorful wings of a butterfly. In these examples, the color changes depending on the angle of view.
Vignolini was inspired by the iridescent colors of the natural world caused by the structure of a material rather than the presence of pigments. The shiny metallic blue fruit of the Marble Berry (Pollia Condensate) is one of the most striking examples that Vignolini has studied, with reflectance of the color that changes between cells and gives the fruit a shiny appearance. A different example is the Cyphochilus beetle, which it found to be whiter than paper thanks to ultra-fine scales that deflect all colors.
Structural color
Vignolini’s lab has used structural color to make fully biodegradable pigments and glitter , which could be used in makeup or confetti, for example. Conventional glitter is made of polymer microparticles, while Dr. Vignolini’s glitter is made only of specially shaped cellulose.
“It is made from the same material that is found in every cell wall in plants. It makes 40% of a salad “, says the expert about its brightness.” It is not harmful if it is dispersed in the environment, and it is also edible “.
It collaborates with cosmetic companies to generate biodegradable plant-based pigments, including for makeup and skin care.
It is also working on new structural food colorants from organic waste, as the food industry is working to replace synthetic colorants. “We can use the remains of the paper-making processes or agricultural waste, such as mango or banana peel, which is rich in cellulose, and then use it to do the coloring,” Vignolini argues.
Others on the PlaMatSu network are looking beyond color to implement surface ideas drawn from nature. Teams from the University of Friborg, Germany, and the University of Friborg, Switzerland, are analyzing how rough plant surfaces deter insects. They could make biodegradable materials that could be sprayed to prevent insects from feeding on a crop or walls to deter them.
For Professor Gianluca Maria Farinola from the University of Bari, Italy, a synthetic chemist, the beautiful light-manipulating structures of tiny algae called diatoms have many possible uses.
He has investigated molecules and nanostructures for LED technologies, solar cells, and optical devices. While teaching undergraduate environmental science students, he came across diatoms. He was inspired to create bionic algae that can manipulate light for laser technologies or to deliver drugs.
Diatoms
Diatoms are single-celled algae, each encased in silica, its own glass house. These can be fan or rod shaped, zigzag, circular or triangular. “They are beautiful natural objects that have inspired artists, fashion designers and architects,” explains Farinola. They are found in seas, lakes and ponds and make at least 20% of the oxygen we breathe.
“The largest species can be seen with the naked eye, but only as small dots,” continues Farinola. “You cannot appreciate the beauty of its shape and structure.”
Under a microscope, you can see their glass houses filled with pores or with a variety of ridges and elevations. These marks help them focus the best wavelengths of light into the cell for photosynthesis, while scattering or filtering out harmful wavelengths. It turns them into natural photonic structures, which means that they are capable of manipulating light.
“Photonic crystals are used a lot in laser technologies,” said Professor Farinola, and he believes that diatoms can inspire us to create new photonic technologies that could be for light sensing, computing or robotics, for example.
As part of the BEEP network exploring bio-inspired solar collection materials, Professor Farinola is hiring a PhD student to study diatom photosynthesis and create a bionic diatom with an additional piece of light-harvesting equipment: certain molecules.
“We incorporate molecules that cover a range of wavelengths that the diatom does not naturally absorb,” says Farinola. This acts as an artificial antenna to absorb extra light and overload photosynthesis. This should boost the growth of diatoms in a seawater tank.
Professor Farinola’s research can see the cultivation of special diatoms for administering drugs. His laboratory in Bari can modify his greenhouses after removing the cell from inside or attaching a substance to the diatomaceous food to introduce it inside the shell. His group has already attached antioxidant molecules in diatom shells that later hooked up the antibiotic ciprofloxacin, which could potentially be administered into a patient.
In another example, live diatoms took bisphosphonates, which is a drug well known for improving bone status in osteoporosis patients. “Then we eliminate all the living matter and we are left with silica with bisphosphonate,” confirms Farinola. He envisions covering an implant with these silica coatings to stimulate bone growth after surgery, although this has yet to be tested in patients.
His team is also studying how silica from diatom shells could be used to clean up different pollutants from the environment. The researchers covered the dead diatom shells with a special polymer (polydopamine) and attached enzymes that could, in principle, be used to break down pollutants, the expert says.
By bringing together biologists, algae experts, physicists, synthetic chemists and emerging researchers, BEEP aims to explore how microorganisms can help us generate new technologies.
“We want to cross the border between biology, chemistry and physics in the context of the study of plants,” says Vignolini, who coordinates BEEP. He believes that this network and PlatMaSu hope that they will allow new and more ecological materials that satisfy social needs.
Original article
This article was originally published in Horizon, the EU Research and Innovation Magazine
