Skoltech researchers have made another breakthrough in their investigation of diatoms, the intriguing single-cell algae that may hold many secrets to advanced technological solutions mimicking nature. These algae can serve as models for membranes used in high-performance miniature microphones with low power consumption and for photonic crystals, which are essential for light signal processing in ultrafast and energy-saving devices of the future. Their study has been published in Scientific Reports.
Diatoms are a large group of unicellular algae with unique hard, porous shells made of silicon dioxide, known as frustules. They are incredibly successful life forms and account for as much as a quarter of the Earth’s organic material. Diatoms capture carbon dioxide via photosynthesis and provide around one-fifth of the entire oxygen supply on the planet, making them one of the principal components of plankton.
According to Alexey Salimon, a senior research engineer at Skoltech Engineering and Chair of Physical Chemistry at NUST MISIS, who has been facilitating the long-term collaboration in applied materials engineering between the two institutes, “The evolutionary success and importance of diatoms to the Earth habitat means that their structure is optimal simultaneously in many respects – photonically, mechanically, biochemically – while also minimizing weight and material consumption.”
The intricate, lace-like exoskeletons of diatoms “provide an unending source of inspiration for the development of new materials and devices,” according to the article in Scientific Reports. They are already used to remove heavy metals from water and as mild abrasives in toothpaste. Microelectromechanical systems and photonic integrated circuits are among the technologies that could benefit from components mimicking diatom frustules. The former serves as the foundation for MEMS microphones, which are sensitive, compact, and energy-efficient. The latter are microchips that operate on photons, providing a faster and more energy-efficient alternative to today’s microelectronics.
The lead author of the study, Skoltech Photonics Ph.D. student Julijana Cvjetinovic, commented that “To use these structures in biomimetic technology, engineers need to have a detailed understanding of their behavior and composition. This particular study provides unprecedented new insights into how the static and dynamic mechanical properties of diatom frustules relate to their structure.”
Diatoms have been the focus of scientists since the invention of the optical microscope in the 17th century. Although our knowledge of these algae is still incomplete, our microscopy tools have become more advanced and versatile.
Alexander Korsunsky from the University of Oxford, the co-principal investigator of the study and a visiting professor at Skoltech, stated, “After a quarter of a century working on this topic, it is satisfying for me to see the good use of nanoindentation inside the Tescan Solaris focused ion beam scanning electron microscope, which was acquired by Skoltech upon my recommendation and is now located at the Institute’s Advanced Imaging Core Facility.”
Thanks to the virtuoso use of a complex setup by Eugene Statnik and Pavel Somov, the research team was able to collect unique video evidence of diatom deformation, while Sergey Luchkin’s expert application of atomic force microscopy allowed for the quantitative evaluation of the elastic modulus and hardness.
Using a combination of atomic force microscopy and nanoindentation, the team examined the mechanical properties of dried and wet frustules with intact organic material. The analysis included hardness, flexibility, and vibrational characteristics, investigating how they relate to the complex structure of the frustules with two layers and distinct patterns of pores on the inside and outside. The studied algae ranged from 30 to 40 micrometers in diameter.
“The most exciting feature we have identified is the distinction between the harder inner layer that serves as a foundation and the softer and more porous outer layer on top of it. It was fascinating to observe the frustules oscillate but not break under cyclic loading, confirming our assumptions about their flexibility and strength. We are the first to observe this behavior and report the comparative mechanical characteristics of living diatom cells and cleaned frustules without organic components,” added Cvjetinovic.
Professor Dmitry Gorin, who leads Skoltech’s Biophotonics Lab and is a co-principal investigator of the study, believes that further investigations into diatom frustules will eventually lead to a diverse range of anticipated applications, including MEMS microphone membranes that resemble algae and composite materials that replicate the diatom structure and incorporate additional components and functions.