In a new study conducted at UCSB and published in The Optical Society’s journal Optica, ICB Founding Director Emeritus Daniel Morse and ICB postdoctoral fellow and lead autor Amitabh Ghoshal, discovered that some species of giant clams produce their white coloration much like the displays used in televisions and smartphones—by combining red, green and blue light.
The team focused on two species of giant clam—Tridacna maxima and Tridacna derasa—and the symbiotic photosynthetic algae with which they cohabitate. The clams produce a collection of iridescent cells just inside the edge of their shells. These cells create a dazzling array of colors including blues, greens, golds and, more rarely, white. “We are studying the clams to see how their iridescent cells interact with the algae to enhance photosynthesis,” said Amitabh Ghoshal. “Like solar cells, photosynthesis involves converting light into energy. As we expand our understanding of the clam’s system for light collection, we can take the lessons from it to create solar cells that more efficiently convert light to energy.” The researchers were surprised to find that the two species of giant clams used different methods for mixing colors to produce white. White in the Tridacna maxima clam comes from tight clusters of differently colored iridescent cells while Tridacna derasa has multicolored individual cells that appear white on a macroscopic scale. “As far as we know, there is no reason or advantage to having differently colored separate cells compared to individual cells with multiple colors in them,” said Ghoshal. “It is possible that one species has the genetic tools for one configuration, and the other species has the tools to make the other configuration but we don’t know that yet.”
Although accomplished in different ways, both clam species create white by mixing clusters of colors much like the electronic displays found in televisions, smartphones and electronic billboards by mixing red, blue, and green pixels to make white. However, most of today’s displays must generate light using LEDs or another light source while the clams require only sunlight. The clam’s iridescent cells contain tiny multi-layer structures of proteins that act like mirrors to reflect various wavelengths of light to produce the colors. “If we could create and control structures similar to those that generate color in the clams, it might be possible to build color-reflective displays that work with ambient light sources such as sunlight or normal indoor lighting,” said Ghoshal. “Producing color the way giant clams do could lead to smartphone, tablet and TV screens that use less power and are easier on the eyes.”
Ghoshal and Morse are now collaborating with ICB Task Order Leader and UCSB chemistry and materials professor Guillermo Bazan to design and test solar cells with structures similar to those found in the clams. They seek to determine whether it is possible to increase the efficiency of synthetic solar cells. “If we could use what we learned from the clams to build a very efficient, distributed light-gathering system, then we could use that to make more efficient three-dimensional solar cells that require less area than our present rooftop and land-based solar farms,” Ghoshal said.
Optica is an open-access, online-only journal dedicated to the rapid dissemination of high-impact peer-reviewed research across the entire spectrum of optics and photonics. Published monthly by The Optical Society, Optica provides a forum for pioneering research to be swiftly accessed by the international community, whether that research is theoretical or experimental, fundamental or applied.