Organic Crystals can Be Bent, Deformed, and Twisted without Breaking


Gallium crystals before a process of manufacturing crystal related products. / Photo by: Foobar via Wikimedia Commons


Most crystals used in industrial and manufacturing settings are brittle and inelastic, making them inappropriate components for certain devices. But, a team of scientists engineered bendable crystalline organic materials that can be used for advanced microscopic electronics.

 In the molecular level, scientists have discovered that crystals can be bent without destroying the material through proper adjustments. However, some crystals have a bending limit before they reach the breaking point.  Scientists at New York University, Abu Dhabi and the National Institute of Technology, India developed a novel concept of molecular soft crystals that can be bent, deformed, and twisted using different external forces.

The crystals are organic in nature and their crystallinity came from the arrangement of the molecular layers, held in place via specific interactions such as hydrogen bonding. In the study, the crystals involved contained two different molecules -- probenecid and 4,4’-azopyridine. Probenecid is a drug component usually prescribed to improve the excretion of uric acid, while the 4,4’-azopyridine is a heteroaromatic azo compound that bends when exposed to UV radiation.

The crystals that exist from the two molecules were composed of stacked 2D layers that were arranged in a criss-cross formation. When the scientists applied heat, the sheets of the crystals twisted but untwisted when exposed to cool temperature. Next, they exposed the crystals to UV light and the material bent quickly. Finally, they applied mechanical force to see if the crystals would break but these would only deform and reform.

“The photo‐ and thermomechanical effects and self‐healing capabilities of the material are rooted in reversible trans-cis isomerization of the azopyridine unit and crystal‐to‐crystal phase transition,” scientists noted.

If fully developed, the crystals can become eligible parts of microrobots, flexible electronics, optical devices, and other products.