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46 The PCB Magazine • April 2015 al can receive information from the patient's wearable system in real time status and make some tweaks, via a phone call, or notify the pa- tient to come in for a visit. Matties: It's an exciting time to be alive. Of course, when the toaster came along that was pretty exciting. Vrtis: That was pretty cool, too! (laughs) Matties: Not that I remember it specifically, but I can imagine, "Look what we can do with our bread!" Okay, moving right along, in terms of Multek and Flextronics, where's the manufacturing taking place? Vrtis: We manufacture globally. Flextronics has more than 200K employees operating in more than 100 locations in 30 countries. Our high-volume manufacturing in Multek takes place in Northfield, Minnesota, and Zhuhai, China. In total, we have an annual capacity of more than 36 million square feet of print- ed circuits. And we continue to make invest- ments in additional capacity and technologies to grow our business. We support every indus- try and we're in every industry where print- ed circuits are needed. We leverage earnings across multiple industry applications to help enable solutions in the wearable market, and we provide printed circuit technology to au- tomotive, aerospace, white goods, infrastruc- ture and mobile communications. So we have a very broad knowledge base to service these markets. Matties: Joan, thank you for sharing your story with us. Vrtis: Thank you. I appreciate the opportu- nity. PCB the Challenges of the fast-Moving WearaBles Market continues IntervIew Topological insulators are an exceptional group of materials. Their interior acts as an in- sulator, but the surface conducts electricity ex- tremely well. Scientists at the Technische Uni- versität München can now measure this for the first time directly, with extremely high temporal resolution and at room temperature. In addition, they succeeded to influence the direction of the surface currents with a polarized laser beam. About ten years ago, sci- entists discovered a group of materials called "topologi- cal insulators" with unusual properties. The interior acts as an insulator, but the top three nanometers conduct electricity better than aver- age. A group led by Profes- sor Alexander Holleitner has succeeded for the first time, to measure this charge current with picosecond resolution at room temperature. They also made the sensational discovery that they can direct the current by the help of circularly polarized light. The best-known representatives of topologi- cal insulators are bismuth selenide or telluride. Scientists account a phenomenon of quantum physics for the exceptionally high conductivity of their surfaces. One observes that all electrons moving in the surface layers have a well-defined spin. Hereby, they differ "topologically" from electrons inside the material. The direction of the surface currents is directly linked with the elec- tron spin. An electron with positive spin always flows in the opposite direction as an electron with negative spin. "The light polariza- tion controls the direction of the photocurrents. This is very fascinating and it re- sults from the coupling of the electron motion with its spin", said Holleitner. Fascinating Quantum Transport on a Surface