Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


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


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


Michael Dorsey | EurekAlert!

More articles from Materials Sciences:

nachricht From ancient fossils to future cars
21.10.2016 | University of California - Riverside

nachricht Study explains strength gap between graphene, carbon fiber
20.10.2016 | Rice University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

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...

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

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...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

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...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>