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MIT Solar Cells are as Light as a Soap Bubble

 

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

In this initial proof-of-concept experiment, the team used a common flexible 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 encapsulation layers, and different types of thin-film solar cell materials, including quantum dots or perovskites, could be substituted for the organic layers used in initial tests.

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

Generally, 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 engineered to respond to light, allowing researchers to guide the bots’ motion. The findings 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 flexibility in the design and the motion. 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 field, but found that electricity can cause adverse side effects to a biological environment and does not allow for selective simulation of distinct regions of muscle to steer the bio-bot.

The researchers begin by growing rings of muscle tissue from a mouse cell line. The muscle cells have a gene added so that a certain wavelength of blue light stimulates the muscle to contract, a technique called optogenetics. The rings are looped around posts on 3-D-printed flexible backbones, ranging from about 7 mm to 2 cm in length. The team also experimented with exercising the muscle rings by triggering the muscle with a flashing light, which made them stronger and allowed the bots to move farther with each contraction.

 

Wearable Patch May Help Manage Diabetes Painlessly

Researchers at Seoul National University have developed an experimental wearable device that can literally take the pain out of managing diabetes and may lead to a new class of wearable medical devices.
The wearable, made out of lightweight graphene, uses a patch to monitor blood sugar levels via sweat, and delivers the drug metformin through the skin with microneedles.

“Diabetics are reluctant to monitor their blood glucose levels because of the painful blood-gathering process,” said study author Hyunjae Lee. “We highly focused on a noninvasive monitoring and therapy system for diabetics.”Diabetics may soon be able to monitor and regulate their blood sugar by wearing a flexible band that uses the wearer’s sweat to track blood glucose levels.

Currently, diabetics have two options for monitoring blood sugar levels. One option is a blood glucose monitor that requires the user to prick their finger to draw out blood for testing. The second option is continuous glucose monitoring, which involves the placement of a sensor underneath the skin and worn constantly. Both options are invasive and can be painful.

The patch can also measure pH, temperature, and humidity, which keeps an eye on how much sweat the user generates. That way, “the person who perspires heavily wouldn’t affect the sensing,” said Tae Kyu Choi, another study author from Seoul National University.

Researchers found the device was able to accurately measure blood sugar levels in humans, and tested the microneedles by delivering the diabetes drug metformin to mice. Insulin—the hormone necessary to lower blood sugar for people with type 1 diabetes—wasn’t used because it’s a protein that would be difficult to deliver through microneedles and is sensitive to the heating process that allows the drug to be delivered through the skin. However, should the wearable go forward in development, other drugs that can effectively lower blood sugar may be considered.

The findings were published in the journal Nature Nanotechnology and can be read athttp://bit.ly/1UAWGt7.

 

Flexible “Skin” Reduces Radar Reflection

Iowa State University engineers have developed a new flexible, stretchable and tunable “skin” that uses rows of small, liquid-metal devices to cloak an object from the sharp eyes of radar. By stretching and flexing the polymer skin, it can be tuned to reduce the reflection of a wide range of radar frequencies.
“It is believeThis flexible, stretchable and tunable “meta-skin” can trap radar waves and cloak objects from detection.d that the present meta-skin technology will find many applications in electromagnetic frequency tuning, shielding and scattering suppression,” the engineers wrote in their paper, published in the journal Scientific Reports.

Liang Dong, associate professor; and Jiming Song, professor, were hoping to prove that electromagnetic waves – perhaps even the shorter wavelengths of visible light – can be suppressed with flexible, tunable liquid-metal technologies. What they came up with are rows of split ring resonators embedded inside layers of silicone sheets. The electric resonators are filled with galinstan, a metal alloy that’s liquid at room temperature and less toxic than other liquid metals such as mercury.

Those resonators are small rings with an outer radius of 2.5 millimeters and a thickness of half a millimeter. They have a 1 millimeter gap, essentially creating a small, curved segment of liquid wire. The rings create electric inductors and the gaps create electric capacitors. Together they create a resonator that can trap and suppress radar waves at a certain frequency. Stretching the meta-skin changes the size of the liquid metal rings inside and changes the frequency the devices suppress.

Tests showed radar suppression was about 75% in the frequency range of 8 to 10 gigahertz, according to the paper. When objects are wrapped in the meta-skin, the radar waves are suppressed in all incident directions and observation angles. “Therefore, this meta-skin technology is different from traditional stealth technologies that often only reduce the backscattering, i.e., the power reflected back to a probing radar,” the engineers wrote in their paper. The idea is that this meta-skin could one day coat the next generation of stealth aircraft.

 

The Freedom of AM

As additive manufacturing (AM) evolves from rapid prototyping to the end-of-use product manufacturing process, manufacturing constraints have been largely alleviated and design freedom for part consolidation is extremely broadened. An AM-enabled part consolidation method promises a more effective way to achieve part count reduction and the ease of assembly compared with traditional Design for Manufacture and Assembly (DFMA) method. However, how to achieve AM enabled part consolidation is not well developed. In a paper authored by Sheng Yang, Yunlong Tang, and Yaoyao Fiona Zhao from McGill University, a new part consolidation method is proposed, characterized by two main modules. The first one is to achieve better functionality through surface-level function integration and sequential part-level function integration based on design specifications with an initial CAD model which is designed for conventional manufacturing process. The other module is to realize better performance through the introduction and optimization of heterogeneous lattice structures according to performance requirements. An example of a triple clamp is studied to verify the effectiveness of the proposed model.

The results include a part count reduced from 19 to 7 and a weight reduction of 20%, as well as better part performance. The paper was published in SME’s Journal of Manufacturing Processes and can be read online here: http://tinyurl.com/PartConsolidation.

This article was first published in the May 2016 edition of Manufacturing Engineering magazine. Read “MIT Solar Cells are as Light as a Soap Bubble” as PDF.


Published Date : 5/1/2016

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