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56 DESIGN007 MAGAZINE I FEBRUARY 2018 haunted by past nightmares of black-pad prob- lems with oxidation treatments, and so are rightly cautious about adopting new processes for bonding without a concrete demand. Key points: Smoother copper and lower loss laminates are critical to lower insertion loss. Where you choose to focus primarily depends on the geometries you are working with and the type of material you have chosen to start with. When working with smooth copper, bear in mind that the copper you specify does not appear on every layer, as the fabricator has to plate up the layers with drill ends to make the vias conductive! For now, PCB fabrication is still a subtractive process in the vast majority of cases. As always, if you are moving into a new area of expertise as a designer, you should be com- fortable in discussing the critical areas of your design with your fabricator, who will be happy to help and likely to save you both time and money. DESIGN007 Martyn Gaudion is managing director of Polar Instruments. To contact Gaudion, or read past columns, click here. Searching for a power outlet may soon become a thing of the past. Instead, devices will receive electricity from a small metallic tab that, when attached to the body, is capable of generating electricity from bending a finger and other simple movements. That's the idea behind a collaborative research project led by University at Buffalo and Institute of Semiconduc- tors (IoP) at Chinese Academy of Science (CAS). The tab—a triboelectric nanogenerator—is described in a study pub- lished online January 31 in the journal Nano Energy. "No one likes being tethered to a power outlet or lugging around a portable charger. The human body is an abun- dant source of energy. We thought: 'Why not harness it to produce our own power?'" says lead author Qiaoqiang Gan, PhD, associate professor of electrical engineering in UB's School of Engineering and Applied Sciences. Researchers have proposed numerous nanogenerators that utilize the triboelectric effect; however, most are dif- ficult to manufacture (requiring complex lithography) or are not cost effective. The tab that the UB and CAS team are developing addresses both of those concerns. It consists of two thin layers of gold, with polydimethyl- siloxane (PDMS) sandwiched in between. The study describes a small tab (1.5 centi- meters long, by 1 centimeter wide). It delivered a maximum voltage of 124 volts, a maximum current of 10 microamps and a maximum power density of 0.22 millwatts per square centi- meter. That's not enough to quickly charge a smartphone; however, it lit 48 red LED lights simultaneously. Co-authors of the study include Huamin Chen at IoP and CAS; and Nan Zhang, a PhD student at UB. Because the tab is easily fabricated, Zhang is leading a team of UB undergraduates which is tasked with improving the tab's perfor- mance. The team plans to use larger pieces of gold, which when stretched and folded together are expected to deliver even more electricity. Your Gadget's Next Power Supply? Your Body