Artificial skin that bestows the sense of touch on prosthetic limbs. Nanochips that control the latest smart phones and devices. Sheets of low cost solar cells as easy to install as unrolling a carpet. All future scenarios, yes, but ones that EECS associate professor Ali Javey is working to realize in the next decade or so.
Javey, a chemist by training, develops new electronic materials and methods of processing existing materials destined for future applications. Working at the confluence of electrical engineering and materials science, chemistry and physics, Javey has already achieved several breakthroughs, including a novel method for nanowire printing. Since arriving at Berkeley five years ago, he’s collected an armload of awards and accolades, including the IEEE Nanotechnology Early Career Award, Technology Review’s Young Innovators under 35 Award, a National Science Foundation CAREER Award and the National Academy of Sciences Award for Initiatives in Research.
Slackers take note: Javey is 29.
To maintain such a pace, Javey and his research team work like mad. In the last six months alone, he has delivered seven invited talks and coauthored 10 journal papers. But explaining his ideas in academic circles isn’t the end goal. Javey wants to develop technologies that industry will adopt.
With that mindset, he should be at the helm of a startup or corporate research division. While it has crossed his mind, he says, the freedom to pursue any old idea keeps him happily on campus, along with the pleasure of teaching and working with Berkeley students. And right now, with the help of 16 graduate students and postdoctoral researchers, he’s exploring several big ideas in nanotechnology.
Carpets of solar cells
The most efficient solar cells are made from single-crystalline compound semiconductors so expensive they’re used only in space, where performance is paramount.
Javey wants to bring them down to earth. He’s developed a new mechanism that controllably grows almost any semiconductor in single-crystalline form on the most everyday of materials—aluminum foil. Because the foil is flexible, the cells can be rolled out like carpet for faster installation, installed over uneven surfaces or packed into small spaces.
“We’ve not only reduced the cost by reducing the amount of material, but we’ve also eliminated steps in the process,” Javey explains.
Computer models predicted the cells’ efficiency to be about 25 percent, comparable to state-of-the-art solar cells; but in early lab experiments, the new method resulted in an efficiency of just 6 percent. “We have the process and proof of concept, but we have to push for that performance limit,” Javey says. “There’s a lot of work to do.” The potential payoff is so great that Mohr Davidow Ventures of Menlo Park is funding the project.
Squeezing more out of Moore
According to Moore’s law, computing power increases as transistors get smaller and smaller, eventually hitting the nanometer limit. At those tiny dimensions, processing silicon to make nano-size computer chips becomes incredibly difficult. Javey’s team finds this challenge irresistible and is investigating new processing methods.
To make silicon conductive, manufacturers randomly introduce an impurity using a process called doping. At the nanoscale level, doping must be approached in a more organized fashion. Using classical surface chemistry, Javey and his team very controllably and deterministically placed doping atoms on the surface of silicon in a one-molecule layer and bonded it to the surface. Once there, researchers gave the material a quick shock, and the atoms dropped down a few layers, resulting in conductive silicon.
“Industry is exploring this approach and getting even better results than we did,” Javey reports.
Artificial skin, authentic touch
In another area of semiconductor processing, researchers have discovered how to print lines of semiconductors, much the same way an inkjet printer prints color ink, using organic materials like polymers. It’s fast and easy, but performance is poor, especially if a high-speed device operates at a low voltage.
Javey thinks he can improve the performance by using inorganic single-crystalline semiconductors, and his team has developed a novel method for producing them. Within minutes, researchers grow a forest of nanowires on a cylindrical drum. “It looks like a bad hair day,” Javey says. “The wires stick out every which direction from the drum.”
Researchers then roll the drum in a controlled way onto a sticky substrate, often paper, plastic or glass, and during the rolling process, the nanowires get dragged and aligned. They anchor to the sticky surface and break off. “As a result, we get a well-aligned nanowire array,” Javey says, from which sheets of electronic material can be built.
One use might be artificial skin for prosthetic applications. As advanced prosthetics are integrated into the brain to control joints, Javey has proposed adding electronic skin and linking it with the brain so patients could regain their sense of touch. The skin might also be used in robotics, governing how much pressure a robot applies to an object.
Javey’s colleagues admire his ability to translate basic science into working ideas. “Research in basic science is hard and research in applied technology is hard,” says John Rogers, professor of materials science and chemistry at University of Illinois, Urbana-Champaign. “Ali does both and makes it look easy.”
In just a short time, Javey has established a breakneck rate of accomplishment, something he credits to his hard-working students. “We don’t know if these projects will work because no one has ever done them before,” he hedges. “It’s high risk, potentially high reward. That’s the cool thing about the type of stuff we’re doing.”