Lotus blossoms are beautiful, and always immaculately clean. Water drops bead up and roll off of their water-repellent surface, washing away every speck of dust. This type of self-cleaning surface would be very useful to us as well: no more carwash, no soiled facades on houses—the potential uses are endless. To date, however, technology has not been able to duplicate nature’s success. Researchers led by Kingo Uchida and Shinichiro Nakamura have now synthesized a compound in the diarylethene family whose surface becomes super-water-repellent on command.
The secret behind the lotus effect is the special microstructure, consisting of tiny nubs, on the surface of the lotus plant’s leaves. These micronodules provide no surface on which water drops can collect, so the leaf does not get coated with water. The drops contract into beads and roll off the surface, sweeping away any particles of dirt they encounter on the way. On normal smooth surfaces, water drops coat the surface and assume a hemispherical shape. Instead of rolling, they then glide over the surface, which does not allow them to remove dirt particles.
The Japanese researchers have now synthesized a special substance, a member of the group of compounds known as diarylethenes, and produced a microcrystalline film of this substance on a support. Electron microscopy images show that the surface of this film is initially smooth. When the diarylethene film is irradiated with UV light, the previously colorless surface turns blue—and is no longer smooth. Instead it is covered with a fine down of tiny fibers that have a diameter of about 1 µm. This down has a similar effect to the micronodules on the lotus blossom, resulting in a super-water-repellent surface. If the surface is irradiated again, this time with visible light, the fibers and color vanish, leaving a colorless, smooth, and wettable surface.
This effect originates from changes in the molecular structure. The diarylethene molecule is made of three five-membered rings hooked together. UV light sets off a rearrangement within the molecule (isomerization). This results in a ring closure, which leads to formation of a fourth ring. The isomer with the closed fourth ring crystallizes in the form of needles, which grow out of the crystals of the isomer with the open ring as soon as a certain concentration is reached. Light in the visible range of the spectrum sets off the reverse reaction: the ring re-opens, and the needles disappear.
Author: Kingo Uchida, Ryukoku University, Otsu (Japan), http://www.chem.ryukoku.ac.jp/~uchida/UchidaLab5a.htm
Title: Photoinduced Reversible Formation of Microfibrils on a Photochromic Diarylethene Microcrystalline Surface
Angewandte Chemie International Edition, doi: 10.1002/anie.200602126
| Angewandte Chemie
How nanoscience will improve our health and lives in the coming years
27.10.2016 | University of California - Los Angeles
3-D-printed structures shrink when heated
26.10.2016 | Massachusetts Institute of Technology
Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.
This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...
Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion
Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
27.10.2016 | Materials Sciences
27.10.2016 | Physics and Astronomy
27.10.2016 | Life Sciences