Single nanomaterial yields many laser colors

Engineers at Brown University and QD Vision Inc. have created nanoscale single crystals that can produce the red, green, or blue laser light needed in digital displays. The size determines color, but all the pyramid-shaped quantum dots are made the same way of the same elements. In experiments, light amplification required much less power than previous attempts at the technology. The team’s prototypes are the first lasers of their kind.

PROVIDENCE, R.I. [Brown University] — Red, green, and blue lasers have become small and cheap enough to find their way into products ranging from BluRay DVD players to fancy pens, but each color is made with different semiconductor materials and by elaborate crystal growth processes. A new prototype technology demonstrates all three of those colors coming from one material. That could open the door to making products, such as high-performance digital displays, that employ a variety of laser colors all at once.

Vertical-cavity surface-emitting laser
Colloidal quantum dots — nanocrystals — can produce lasers of
many colors. Cuong Dang manipulates a green beam that pumps
the nanocrystals with energy, in this case producing red laser
light. Credit: Mike Cohea/Brown University

“Today in order to create a laser display with arbitrary colors, from white to shades of pink or teal, you’d need these three separate material systems to come together in the form of three distinct lasers that in no way shape or form would have anything in common,” said Arto Nurmikko, professor of engineering at Brown University and senior author of a paper describing the innovation in the journal Nature Nanotechnology. “Now enter a class of materials called semiconductor quantum dots.”

The materials in prototype lasers described in the paper are nanometer-sized semiconductor particles called colloidal quantum dots or nanocrystals with an inner core of cadmium and selenium alloy and a coating of zinc, cadmium, and sulfur alloy and a proprietary organic molecular glue. Chemists at QD Vision of Lexington, Mass., synthesize the nanocrystals using a wet chemistry process that allows them to precisely vary the nanocrystal size by varying the production time. Size is all that needs to change to produce different laser light colors: 4.2 nanometer cores produce red light, 3.2 nanometer ones emit green light and 2.5 nanometer ones shine blue. Different sizes would produce other colors along the spectrum.

The cladding and the nanocrystal structure are critical advances beyond previous attempts to make lasers with colloidal quantum dots, said lead author Cuong Dang, a senior research associate and nanophotonics laboratory manager in Nurmikko’s group at Brown. Because of their improved quantum mechanical and electrical performance, he said, the coated pyramids require 10 times less pulsed energy or 1,000 times less power to produce laser light than previous attempts at the technology.

Quantum nail polish
When chemists at QDVision brew a batch of colloidal quantum dots for Brown-designed specifications, Dang and Nurmikko get a vial of a viscous liquid that Nurmikko said somewhat resembles nail polish. To make a laser, Dang coats a square of glass — or a variety of other shapes — with the liquid. When the liquid evaporates, what’s left on the glass are several densely packed solid, highly ordered layers of the nanocrystals. By sandwiching that glass between two specially prepared mirrors, Dang creates one of the most challenging laser structures, called a vertical-cavity surface-emitting laser. The Brown-led team was the first to make a working VCSEL with colloidal quantum dots.

The nanocrystals’ outer coating alloy of zinc, cadmium, sulfur and that molecular glue is important because it reduces an excited electronic state requirement for lasing and protects the nanocrystals from a kind of crosstalk that makes it hard to produce laser light, Nurmikko said. Every batch of colloidal quantum dots has a few defective ones, but normally just a few are enough to interfere with light amplification.

Faced with a high excited electronic state requirement and destructive crosstalk in a densely packed layer, previous groups have needed to pump their dots with a lot of power to push them past a higher threshold for producing light amplification, a core element of any laser. Pumping them intensely, however, gives rise to another problem: an excess of excited electronic states called excitons. When there are too many of these excitons among the quantum dots, energy that could be producing light is instead more likely to be lost as heat, mostly through a phenomenon known as the Auger process.

The nanocrystals’ structure and outer cladding reduces destructive crosstalk and lowers the energy needed to get the quantum dots to shine. That reduces the energy required to pump the quantum dot laser and significantly reduces the likelihood of exceeding the level of excitons at which the Auger process drains energy away. In addition, a benefit of the new approach’s structure is that the dots can act more quickly, releasing light before Auger process can get started, even in the rare cases when it still does start.

“We have managed to show that it’s possible to create not only light, but laser light,” Nurmikko said. “In principle, we now have some benefits: using the same chemistry for all colors, producing lasers in a very inexpensive way, relatively speaking, and the ability to apply them to all kinds of surfaces regardless of shape. That makes possible all kinds of device configurations for the future.”

In addition to Nurmikko and Dang, another author at Brown is Joonhee Lee. QD Vision authors include Craig Breen, Jonathan Steckel, and Seth Coe-Sullivan, a company co-founder who studied engineering at Brown as an undergraduate.

The US. Department of Energy, the Air Force Office for Scientific Research, and the National Science Foundation supported the research. Dang is a Vietnam Education Foundation (VEF) Scholar.

Three Brown Teams Named Finalists in Rhode Island Business Plan Competition

Three Brown teams, all with connections to the School of Engineering, were named finalists at the 2012 Rhode Island Business Plan Competition. In total, 75 emerging entrepreneurs applied to the competition, and seven have been selected as finalists, including four in the entrepreneur track and three in the student track. All three of the finalists in the student track were from Brown and the School of Engineering.

One of the finalists, JCD Wind, was from Steve Petteruti’s Entrepreneurship I class and Entrepreneurship II classes, Engineering 1930G and Engineering 1930H. JCD Wind, included James McGinn ’12, a biomedical engineering concentrator, and Carli Wiesenfeld ’12, a commerce, organizations, and entrepreneurship (COE) concentrator. The company aims to make seamless, high strength lightweight carbon fiber turbine blades. McGinn is also a member of the men’s rugby team, and Wiesenfeld is a member of the women’s gymnastics team.

A group of four graduate students in the Program in Innovation Management and Entrepreneurship (PRIME) master’s degree program were also among the semifinalists. Solar4Cents included PRIME students Sean Pennino, Bhavuk Nagpal, Xiaotong 'Peter' Shan, and Meng 'Milo' Zhang. Solar4Cents is a manufacturing company that aims to produce low-cost, thin-film copper, zinc, tin, and sulfur solar cells for solar panel manufacturers.

The third finalist in the student track is Overhead.fm, which includes Brown undergraduates Parker Wells '12, a mechanical engineering concentrator, and Stephen Hebson '12, an economics and history double concentrator. Their plan is to produce a web app to provide a customizable stream of music for in-store use, licensing music directly from the artists and labels.

The contest will award more than $200,000 in prizes. In order to receive prizes, applicants must agree to establish or continue operations in Rhode Island. Winners will be announced on May 3 at RIBX 2012 (Business Expo) at the Rhode Island Convention Center in Providence. The event is free and open to the public. All finalists will make brief presentations of their business plans at the Expo. Please go to www.ri-bizplan.com for more details. Established in 2000, the Rhode Island Business Plan Competition has awarded more than $1 million in prizes since its inception.

For the official RI Business plan release on the competition, please go to:
http://www.ri-bizplan.com/DefaultPermissions/2012FinalistsNamed/tabid/258/Default.aspx

For the Providence Business News story on the event, please go to: http://www.pbn.com/Biz-plan-competition-names-finalists,67143?category_id=27&sub_type=stories,packages

Wei Yang PhD ‘85 among eight honorary degree recipients at Brown Commencement

During its 244th Commencement, Brown University will confer eight honorary doctorates: Carolyn Bertozzi, biochemist; Viola Davis, actress; John Lewis, civil rights leader; Marilynne Robinson, writer; Sebastian Ruth, musician; Diane Sawyer, journalist; Gene Sharp, political theorist; and Wei Yang, engineer.

PROVIDENCE, R.I. [Brown University] — Eight people who have distinguished themselves through their efforts in the arts, sciences, letters, scholarship and public service will receive honorary degrees from Brown University at Commencement on Sunday, May 27, 2012:

·         Carolyn Bertozzi, chemist and immunologist;

·         Viola Davis, actress;

·         John Lewis, civil rights leader and U.S. representative;

·         Marilynne Robinson, writer and educator;

·         Sebastian Ruth, musician and educator;

·         Diane Sawyer, broadcast journalist;

·         Gene Sharp, political theorist, scholar of nonviolent change; and

·         Wei Yang, engineer.

Honorary degrees are awarded by the University’s Board of Fellows and are conferred by the University president — in English and in Latin — during Commencement exercises on the College Green.

None of the recipients will speak at the Commencement ceremony; that honor has been reserved since the University’s earliest days for two members of the graduating class. Several of the honorands will, however, participate in Commencement forums and other public presentations during Commencement Weekend. Information about times and places for these and other Commencement presentations will be available from the Office of Media Relations and on the University’s 2012 Commencement webpage.

 

Wei Yang  
Engineer and President of Zhejiang University
Doctor of Science (Sc.D.)

Wei Yang, president of China’s Zhejiang University, is an internationally celebrated engineer and materials science researcher, educator, and administrator. He is a Ph.D. graduate of Brown University.

Born in Beijing, Yang was educated in the United States and China (B.S., Northwestern Polytechnic University, 1976; M.S., Tsinghua University, 1981; Ph.D., Brown University, 1985). Four years after earning his Ph.D., Yang was promoted to a full professor of engineering at Tsinghua University, the youngest person ever to achieve that rank.

In addition to continuing an active and very productive career as a research engineer in fracture mechanics, mechatronic reliability, and micro/nanomechanics (11 books and 211 technical papers in internationally refereed journals), Yang has served in a number of national and international positions as an educator and administrator. He became director of the Failure Mechanics Laboratory of the Chinese Ministry of Education in 1993. For seven years (1997–2004), he headed the Department of Engineering Mechanics at Tsinghua, also serving for a time as executive dean of the Aerospace School. From 2004 to 2006, he served as director-general of the Academic Degrees Committee of the State Council of China and also headed the Directorate of Graduate Education. He began as president of Zhejiang University, one of China’s largest and oldest universities, in 2006.

As head of the Chinese Academy of Sciences Technological Science Division, Yang has had extensive international scientific experience. He has served as regional editor for several journals in the field of composite materials and has been on the editorial boards of the International Journal of Fracture, Fatigue & Fracture of Engineering Materials & Structures, and the Archive of Applied Mechanics, among several others. Early in 2009, Yang became widely known for a stern and dedicated fight against scientific misconduct, dealing strictly with researchers found to have engaged in misconduct and proactively developing training programs to support scientific integrity. Organizations and journals,Nature among them, praised his zero tolerance policies.

Yang has supported and worked for collaborations with universities in the United States, Germany, the Netherlands, Singapore and elsewhere. His own postgraduate students — more than 40 of them — have extended his international reach. More than 10 of them hold engineering faculty positions in the United States and Europe. He has been honored extensively for his efforts, including the 2009 Brown University Engineering Alumni Medal.

Five Brown Teams Named Semifinalists in Rhode Island Business Plan Competition

Five Brown teams, including three with connections to the School of Engineering, were named semifinalists at the 2012 Rhode Island Business Plan Competition. In total, 75 emerging entrepreneurs applied to the competition, and 13 were selected as semifinalists, including seven in the entrepreneur track and six in the student track. Five of the six semifinalists in the student track were from Brown, including three teams from the School of Engineering.

Two teams from Steve Petteruti’s Entrepreneurship I class and Entrepreneurship II classes, Engineering 1930G and Engineering 1930H, were among the semifinalists. JCD Wind, included James McGinn ’12, a biomedical engineering concentrator, and Carli Wiesenfeld ’12, a commerce, organizations, and entrepreneurship (COE) concentrator. The company aims to make seamless, high strength lightweight carbon fiber turbine blades. McGinn is also a member of the men’s rugby team, and Wiesenfeld is a member of the women’s gymnastics team.

Another semifinalist was CityBase Security, which included Julianne Bishop ’12 and Joschka Tryba ’12, who are both COE concentrators. Their company hopes to provide a map-based platform that will integrate communication and information systems for both emergency responders and public reporting of incidents/crimes.

A group of four graduate students in the Program in Innovation Management and Entrepreneurship (PRIME) master’s degree program were also among the semifinalists. Solar4Cents included PRIME students Sean Pennino, Bhavuk Nagpal, Xiaotong 'Peter' Shan, and Meng 'Milo' Zhang. Solar4Cents is a manufacturing company that aims to produce low-cost, thin-film copper, zinc, tin, and sulfur solar cells for solar panel manufacturers.

The contest will award more than $200,000 in prizes. In order to receive prizes, applicants must agree to establish or continue operations in Rhode Island. Winners will be announced on May 3. Please go to www.ri-bizplan.com for more details. Established in 2000, the Rhode Island Business Plan Competition has awarded more than $1 million in prizes since its inception.

For the official RI Business plan release on the competition, please go to: http://www.ri-bizplan.com/DefaultPermissions/SemifinalistsNamed/tabid/257/Default.aspx

For the Providence Business News story on the event, please go to: http://www.pbn.com/Biz-plan-competition-names-semi-finalists,66767?category_id=27&sub_type=stories,packages

For the GoLocalProv.com story, please go to: http://www.golocalprov.com/business/new-ri-business-plan-competition-2012-names-semi-finalists/

Bats save energy by drawing in wings on upstroke

Bat wings are like hands: meaty, bony and full of joints. A new Brown University study finds that bats take advantage of their flexibility by folding in their wings on the upstroke to save inertial energy. The research suggests that engineers looking at flapping flight should account for wing mass and consider a folding design.

PROVIDENCE, R.I. [Brown University] — Whether people are building a flying machine or nature is evolving one, there is pressure to optimize efficiency. A new analysis by biologists, physicists, and engineers at Brown University reveals the subtle but important degree to which that pressure has literally shaped the flapping wings of bats.

The team’s observations and calculations show that by flexing their wings inward to their bodies on the upstroke, bats use only 65 percent of the inertial energy they would expend if they kept their wings fully outstretched. Unlike insects, bats have heavy, muscular wings with hand-like bendable joints. The study suggests that they use their flexibility to compensate for that mass.

“Wing mass is important and it’s normally not considered in flight,” said Attila Bergou, who along with Daniel Riskin is co-lead author of the study that appears April 11 in theProceedings of the Royal Society B. “Typically you analyze lift, drag, and you don’t talk about the energy of moving the wings.”

The findings not only help explain why bats and some birds tuck in their wings on the upstroke, but could also help inform human designers of small flapping vehicles. The team’s research is funded by the U.S. Air Force Office of Sponsored Research.

“If you have a vehicle that has heavy wings, it would become energetically beneficial to fold the wings on the upstroke,” said Sharon Swartz, professor of ecology and evolutionary biology at Brown. She and Kenneth Breuer, professor of engineering, are senior authors on the paper.

The physics of flexed flapping
The team originally set out to study something different: how wing motions vary among bats along a wide continuum of sizes. They published those results in 2010 in the Journal of Experimental Biology, but as they analyzed the data further, they started to consider the intriguing pattern of the inward flex on the upstroke.

That curiosity gave them a new perspective on their 1,000 frames-per-second videos of 27 bats performing five trials each aloft in a flight corridor or wind tunnel. They tracked markers on the bats, who hailed from six species, and measured how frequently the wings flapped, how far up and down they flapped, and the distribution of mass within them as they moved. They measured the mass by cutting the wing of a bat that had died into 32 pieces and weighing them.

The team fed the data in to a calculus-rich model that allowed them to determine what the inertial energy costs of flapping were and what they would have been if the wings were kept outstretched.

Bergou, a physicisist, said he was surprised that the energy savings was so great, especially because the calculations also showed that the bats have to spend a lot of energy — 44 percent of the total inertial cost of flapping — to fold their wings inward and then back outward ahead of the downstroke.

“Retracting your wings has an inertial cost,” Bergou said. “It is significant but it is outweighed by the savings on the up and down stroke.”

The conventional wisdom has always been that bats drew their wings in on the upstroke to reduce drag in the air, and although the team did not measure that, they acknowledge that aerodynamics plays the bigger role in the overall energy budget of flying. But the newly measured inertial savings of drawing in the wings on the upstroke seems too significant to be an accident.

“It really is an open question whether natural selection is so intense on the design and movement patterns of bats that it reaches details of how bats fold their wings,” Swartz said. “This certainly suggests that this is not a random movement pattern and that it is likely that there is an energetic benefit to animals doing this.”

- by David Orenstein

Sen. Reed, federal and state officials tour Brown’s Superfund lab

Sen. Jack Reed, accompanied by the New England regional director of the U.S. Environmental Protection Agency and the directors of the state’s environmental and health departments, visited Brown University’s Superfund Research Program Monday, April 9, 2012. The Brown program is one of 14 research groups funded by the National Institutes of Health.

PROVIDENCE, R.I. [Brown University] — U.S. Sen. Jack Reed (D-RI), the New England regional administrator of the U.S. Environmental Protection Agency, and the directors of the state departments of Environmental Management and Health, visited Brown University’s Superfund Research Program Monday, April 9. 2012. The Brown lab is one of 14 research groups funded by the National Institutes of Health to assess and remediate Superfund sites nationwide.

Brown’s Superfund research group has been in operation since 2005. The program has brought in some $43 million in funding to Rhode Island since then, creating or supporting 45 jobs in the Ocean State. The group is working on the Centredale Manor Superfund site in Providence, the Gorham Manufacturing site in Providence, and the well-publicized soil contamination affecting residential properties in the Bay Street neighborhood in Tiverton. In these cases, scientists and students have tracked the flow of hazardous gases from contaminated sites, identified and tested toxic chemicals, worked with community and neighborhood associations and state and federal agencies to clean up contaminated areas, and offered insights into how chemicals can alter human health and reproduction.

“Rhode Island is a small, densely populated state with a proud industrial heritage, yet burdened by a toxic legacy,” said Kim Boekelheide, professor of medical science and a member of Brown’s Superfund research group. “Brown’s Superfund Research Program is a center of technical excellence, where we focus on new scientific approaches to clean up our post-industrial legacy of contaminated sites here in the Ocean State and throughout the nation.”

Reed toured the Brown group’s facility in the Laboratories for Molecular Medicine, 70 Ship St. in Providence, at 12:30 p.m. He was accompanied by Gwen Collman, director of extramural research and training, National Institute of Environmental Health Sciences (NIEHS), the program’s primary funder; Curt Spalding, New England administrator for the EPA; Janet Coit, Rhode Island Department of Environmental Management director; and Michael Fine, Rhode Island Department of Health director. Brown Provost Mark Schlissel also toured the facility.

The agenda for the visit is available online.

“Putting people to work to reduce the negative impacts of abandoned hazardous waste sites is a smart investment to protect public health, the environment, and our economy,” said Reed. “I am pleased that Brown’s federally funded Superfund Research Program is working through targeted research and community outreach to address health concerns and design novel techniques to reduce toxic chemicals at Superfund sites in Rhode Island.”

In addition to working on contaminated sites in Rhode Island, the Brown Superfund Research Program connects to Superfund sites nationwide, primarily through research. Specifically, the group has:

• Devised a computational model with the Rhode Island Department of Environmental Management to track the flow of contaminant vapors from groundwater and soil into homes and businesses. The model has been tested at the Gorham site in Rhode Island and is currently being tested at a hazardous waste site in Somerville, Mass.
• Investigated the potential environmental hazards from consumer products using nanomaterials (dimensions one-billionth of a meter, or 1/50,000th the width of a human hair). Current projects are looking at the release of nanosilver into sewer systems, how nanomaterials break down in landfills and how they infiltrate human lungs.
• Studied the effects of chemicals on human sperm and human female reproduction, especially pregnant women and chemically induced premature births.

Superfund-sized clean-up
Postdoctoral Researcher Pengpeng Grimshaw takes samples
from a Rhode Island riverbank to assess possible contaminant
levels and study novel cleanup processes that have been
developed in a Superfund lab at Brown.

The Brown Superfund Program has created innovative ways to connect with local communities and develop the next generation of environmental leaders. The centerpiece of this effort is the Community Environmental College, an eight-week summer leadership program for inner-city youth. Last year, nearly 50 urban high-school students, primarily in Providence and Pawtucket, engaged in various activities to raise community awareness of the environment, ranging from enlisting Latino restaurants to supply used vegetable oil for biodiesel fuel, recycling mattresses, and encouraging convenience stores to stock healthier food. Brown students work with youth and community groups on myriad projects, including a year-round after-school program called ECO Youth, weatherizing homes and the “Hospitals for a Healthy Environment in Rhode Island” programs, which promotes cost-effective, healthy, and sustainable health-care institutions.

“Through our Community Engagement Core, we help local groups clean up contaminated land and work with legislators and regulators to strengthen state policies on brownfields, school siting, and various environmental justice issues,” said Phil Brown, professor of sociology at Brown and a researcher with the Superfund Research Program. “I am excited about our engagement with so many high school students in the Community Environmental College, as they learn so much and apply themselves to the Healthy Corner Store Initiative, weatherization, green transportation, and other critical concerns.”

The Brown Superfund Research Program is up for renewed funding in 2014. The renewal comes amid a competitive landscape; a decade ago, the federal Superfund Research Program supported 21 such programs nationwide.

“Continued funding will allow us to improve the prediction of the health risks associated with complex chemical exposures and devise new remediation strategies for contaminated sites,” Boekelheide said.

- by Richard Lewis

Brown’s Barrett Hazeltine Named one of America’s “Best 300 Professors” by The Princeton Review

Legendary engineering professor Barrett Hazeltine has been recognized by The Princeton Review as one America’s top undergraduate professors in its latest guidebook, The Best 300 Professors. The book profiles professors in 60 fields based on surveys by The Princeton Review and ratings on RateMyProfessors.com, the highest trafficked college professor ratings site in the country.

Data from RateMyProfessors.com identified more than 42,000 professors, and was culled down to a base list of 1,000 professors. After obtaining further input from university administrators and students, along with The Princeton Review’s surveys of the professors under consideration, the editors of The Princeton Review made the final choices of the professors.

Professor Hazeltine has taught engineering, management, and technology courses at Brown for more than 50 years, and currently teaches Management of Industrial and Non-Profit Organizations, Managerial Decision Making, and Appropriate Technology. He received awards for teaching from thirteen senior classes at Brown, 1972 to 1984, and 1990. In 1985, the award was named after him.

Simple method could aid in medical imaging, chemotherapy

Researchers, led by Robert Hurt, professor of engineering, have found that a simple technique can swathe nanoparticles with a blanket of graphene, which could carry medical imaging contrast agents, allowing the nanoparticles to enhance imaging signals while shielding tissue from their potential toxic effects. They could also deliver chemotherapy drugs to tumors.

Full report online: cen.acs.org/articles/90/web/2012/04/Graphene-Envelops-Nanoparticles.html

Full paper: http://pubs.acs.org/doi/full/10.1021/nl2045952