Scientists Just Made a Game-Changing Discovery: Diamonds Can Produce Electricity

3 min readHere’s what you’ll learn when you read this story:Diamonds have never been considered piezoelectric, since producing electricity requires bending and contorting materials, properties diamonds aren’t exactly known for.A new study created a diamond membrane only a few micrometers thick, flexed the material, and found that diamonds actually are piezoelectric. This could open new opportunities for the material to be used in energy and medical devices beyond being just a passive support material.Diamonds are commonly prized for their dazzling brilliance, but these products of carbon, heat, pressure, and time have utility far beyond being the pretty thing on your finger. Because it’s the hardest naturally-occurring mineral in the world, cutting tools are often made with diamonds so they can rip through the most stubborn of materials. Diamonds can also be reinforced with carbon nanotubes to eliminate their brittle weaknesses. Furthermore, diamond dust could actually help cool the planet. When it comes to diamonds, the hype is real.Although diamonds have been cherished for millennia, scientists are still learning more about these incredible cubic carbon lattices. For more than a century, scientists assumed diamonds weren’t piezoelectric—a term for materials that generate an electrical charge when placed under mechanical stress. To a certain degree, this makes logical sense—after all, diamonds aren’t exactly known for their ability to stretch, squeeze, and deform.And while that’s true for bulk diamonds, a team of researchers from the University of Hong Kong wondered if a thin diamond membrane might be a different story. If diamonds can be piezoelectric, that property would be a game changer for micromechanical systems that rely on diamonds to simply support other piezoelectric materials.In a new study published in the journal Science, scientists aimed to prove the idea, but the first major hurdle was constructing a diamond thin enough to bend. To do this, they grew the diamond membranes on a silicon substrate using microwave plasma chemical vapor deposition (CVD). This acts like a highly-advanced 3D printer that uses microwaves to turn reactive plasmas into thin films, placing them atom-by-atom on a thin substrate. The researchers then carefully removed the diamond membrane using edge-exposed exfoliation and transparent sticky tape that eventually wedged free the two-inch-wide, one-micron-thick diamond membrane. Then, they got to bending.“For controlled bending, the membrane is attached to a durable and flexible polyethylene terephthalate (PET) substrate,” the authors wrote. “By securing one end of the assembled device and applying force on the other end, we can precisely control the deformation of the diamond membrane and measure any resulting electrical outputs.”After conducting these mechanical cycling experiments, the researchers noted—after eliminating possible environmental or triboelectric (aka rubbing) effects—that the diamond did produce an electrical output. They found that asymmetrical grain boundaries, which separate the crystal lattices that make up the membrane, build up electrical charge polarization, creating potential between the membrane’s upper and lower surfaces.“The piezoelectric effect depends on membrane thickness, with the most pronounced response occurring with membranes ~5 μm thick,” the authors wrote. “The asymmetric variations introduced by grain boundaries during diamond synthesis explain why the piezoelectric effect depends on membrane thickness.”Because it’s non-toxic and chemically stable, an electricity-producing diamond membrane could be a big hit with energy and medical industries, possibly becoming a central piece of technology in implants that can power themselves.Diamonds deserve the awe they inspire—in more ways than one.Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.