EurekAlert! -- Researchers in California are reporting development of a so-called “NanoPen” that could provide a quick, convenient way of laying down patterns of nanoparticles — from wires to circuits — for making futuristic electronic devices, medical diagnostic tests, and other much-anticipated nanotech applications. A report on the device, which helps solve a long-standing challenge in nanotechnology, appeared in ACS’ Nano Letters, a monthly journal.