Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists develop a semiconductor nanocomposite material that moves in response to light

18.10.2016

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 in a variety of applications, including microscopic actuators and grippers for surgical robots, light-powered micro-mirrors for optical telecommunications systems, and more efficient solar cells and photodetectors.


A microscopic gripper made with a novel semiconductor material developed at Worcester Polytechnic Institute reaches out for a grasps a plastic bead that is the same size as a human cell. The material, a thin film of molybdenum disulfide encased in a rubber-like polymer, moves in response to exposure to light.

Credit: Small Systems Laboratory, Worcester Polytechnic Institute (WPI)

"This is a new area of science," said Balaji Panchapakesan, associate professor of mechanical engineering at WPI and lead author of a paper about the new material published in Scientific Reports, an open access journal from the publishers of Nature. "Very few materials are able to convert photons directly into mechanical motion. In this paper, we present the first semiconductor nanocomposite material known to do so. It is a fascinating material that is also distinguished by its high strength and its enhanced optical absorption when placed under mechanical stress.

"Tiny grippers and actuators made with this material could be used on Mars rovers to capture fine dust particles." Panchapakesan noted. "They could travel through the bloodstream on tiny robots to capture cancer cells or take minute tissue samples. The material could be used to make micro-actuators for rotating mirrors in optical telecommunications systems; they would operate strictly with light, and would require no other power source."

Like other semiconductor materials, molybdenum disulfide, the material described in the Scientific Reports paper ("Chromatic Mechanical Response in 2-D Layered Transition Metal Dichalcogenide (TMDs)-based Nanocomposites"), is characterized by the way electrons are arranged and move about within its atoms. In particular, electrons in semiconductors are able to move from a group of outer orbitals called the valence band to another group of orbitals known as the conduction band only when adequately excited by an energy source, like an electromagnetic field or the photons in a beam of light. Crossing the "band gap," the electrons create a flow of electricity, which is the principal that makes computer chips and solar cells possible.

When the negatively-charged electrons move between orbitals, they leave behind positively charged voids known as holes. A pair of a bound electron and an electron hole is called an exciton.

In their experiments, Panchapakesan and his team, which included graduate students Vahid Rahneshin and Farhad Khosravi, as well as colleagues at the University of Louisville and the University of Warsaw Pasteura, observed that the atomic orbitals of the molybdenum and sulfur atoms in molybdenum disulfide are arranged in a unique way that permits excitons within the conduction band to interact with what are known as the p-orbitals of the sulfur atoms. This "exciton resonance" contributes to the strong sigma bonds that give the two dimensional array of atoms in molybdenum sulfide its extraordinary strength. The strength of this resonance is also responsible for a unique effect that can generate heat within the material. It is the heat that gives rise to the material's chromatic (light-induced) mechanical response.

To take advantage of the later phenomenon, Panchapakesan's team created thin films made up of just one to three layers of molybdenum disulfide encased in layers of a rubber-like polymer. They exposed these nanocomposites to various wavelengths of light and found that the heat generated as a result of the exciton resonance caused the polymer to expand and contract, depending on the wavelength of the light used. In previous work, Panchapakesan's team harnessed this photo-mechanical response by fabricating tiny grippers that open and close in response to light pulses. The grippers can capture plastic beads the size of a single human cell.

In further testing, Panchapakesan and his team discovered another unique behavior of the molybdenum disulfide composite that opens the door to a different set of applications. Employing what is known as strain engineering, they stretched the material and discovered that mechanical stresses increased its ability to absorb light.

"This is something that cannot be done with conventional thin-film semiconductors," Panchapakesan said, "because when you stretch them, they will prematurely break. But with its unique material strength, molybdenum disulfide can be stretched. And its increased optical absorption under strain makes it a good candidate for more efficient solar cells, photodetectors, and detectors for thermal and infrared cameras.

"The exciton resonance, photomechanical response, and increased optical absorption under strain make this an extraordinary material and an intriguing subject for further investigation," he added.

###

Panchapakesan's research is supported by the National Science Foundation (CMMI: 1463869).

About Worcester Polytechnic Institute

Founded in 1865 in Worcester, Mass., WPI is one of the nation's first engineering and technology universities. Its 14 academic departments offer more than 50 undergraduate and graduate degree programs in science, engineering, technology, business, the social sciences, and the humanities and arts, leading to bachelor's, master's and doctoral degrees. WPI's talented faculty work with students on interdisciplinary research that seeks solutions to important and socially relevant problems in fields as diverse as the life sciences and bioengineering, energy, information security, materials processing, and robotics. Students also have the opportunity to make a difference to communities and organizations around the world through the university's innovative Global Projects Program. There are more than 45 WPI project centers throughout the Americas, Africa, Asia-Pacific, and Europe.

Media Contact

Michael Dorsey
mwdorsey@wpi.edu
508-831-5609

 @WPI

http://www.wpi.edu 

Michael Dorsey | EurekAlert!

More articles from Materials Sciences:

nachricht Multitasking monolayers
25.07.2017 | Vanderbilt University

nachricht Flexible proximity sensor creates smart surfaces
25.07.2017 | Fraunhofer-Institut für Produktionstechnik und Automatisierung IPA

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Carbon Nanotubes Turn Electrical Current into Light-emitting Quasi-particles

Strong light-matter coupling in these semiconducting tubes may hold the key to electrically pumped lasers

Light-matter quasi-particles can be generated electrically in semiconducting carbon nanotubes. Material scientists and physicists from Heidelberg University...

Im Focus: Flexible proximity sensor creates smart surfaces

Fraunhofer IPA has developed a proximity sensor made from silicone and carbon nanotubes (CNT) which detects objects and determines their position. The materials and printing process used mean that the sensor is extremely flexible, economical and can be used for large surfaces. Industry and research partners can use and further develop this innovation straight away.

At first glance, the proximity sensor appears to be nothing special: a thin, elastic layer of silicone onto which black square surfaces are printed, but these...

Im Focus: 3-D scanning with water

3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects

A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

The technology with a feel for feelings

12.07.2017 | Event News

 
Latest News

NASA flights gauge summer sea ice melt in the Arctic

25.07.2017 | Earth Sciences

Fungi that evolved to eat wood offer new biomass conversion tool

25.07.2017 | Life Sciences

New map may lead to drug development for complex brain disorders, USC researcher says

25.07.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>