TECH FRONT THE LATEST RESEARCH AND DEVELOPMENT NEWS IN MANUFACTURING AND TECHNOLOGY t MIT Solar Cells are as Light as a Soap Bubble R


esearchers at the Massachusetts Institute of Technology have developed a solar cell so thin that it can rest on top of a soap bubble without popping it. Though it is years away from being commercially viable, the devel- opment shows a new approach to making solar cells that could help power the next generation of portable electronics. The new process is described in a paper by MIT professor Vladimir Bulovic, research scientist Annie Wang, and doctoral student Joel Jean, in the journal Or- ganic Electronics. Bulovic, MIT’s associate dean for innovation, said the key to the new approach is to make the solar cell, the substrate that supports it, and a protec- tive overcoating to shield it from the environment, all in one process. The substrate is made in place and never needs to be handled, cleaned, or removed from the vacuum during fabrication, thus minimizing exposure to dust or other contaminants that could degrade the cell’s performance. In this initial proof-of-concept experiment, the team used a common fl exible polymer called parylene as both the substrate and the overcoating, and an organic material called DBP as the primary light-absorbing layer. Parylene is a commercially available plastic coating used widely to protect implanted biomedical devices and printed circuit boards from environmental damage. The entire process takes place in a vacuum chamber at room temperature and without the use of any solvents, unlike conventional solar-cell manufacturing, which requires high temperatures and harsh chemicals. In this case, both the substrate and the solar cell are “grown” using established vapor deposition techniques.


The team emphasizes that these particular choices of materials were just examples, and that it is the in-line substrate manufacturing process that is the key innovation. Different materials could be used for the substrate and en- capsulation layers, and different types of thin-fi lm solar cell materials, including quantum dots or perovskites, could be substituted for the organic layers used in initial tests.


To demonstrate just how thin and lightweight the cells are, researchers at MIT placed the cell on top of a soap bubble.


However, the researchers acknowledge that the cell may be too thin to be practical. “If you breathe too hard, you might blow it away,” said Jean.


Miniature Bio-bots See the Light G


enerally, you don’t want to walk towards the light. But researchers at the University of Illinois at Urbana- Champaign want their robots to do just that. In a major step towards the use of robots in health, sensing and the environment, miniature robots have been equipped with muscle cells that have been genetically engi- neered to respond to light, allowing researchers to guide the bots’ motion. The fi ndings were published in the Proceedings of the National Academy of Sciences. “Light is a noninvasive way to control these machines,” Bashir said. “It gives us fl exibility in the design and the mo- tion. The bottom line of what we are trying to accomplish is the forward design of biological systems, and we think the light control is an important step toward that.” Bashir’s group had previously experimented with bio-bots


that were activated by an electrical fi eld, but found that elec- tricity can cause adverse side effects to a biological environ-


May 2016 | AdvancedManufacturing.org 29


Photo courtesy of MIT


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