Cover Image, Volume 50, Issue 7


original image

Micro-mechanical strain sensors are demonstrated by subjecting carbon nanocones to an alternating electric field aligning them into single strings in a polymer matrix, as presented on page 477 by Henrik Høyer, Matti Knaapila, Jakob Kjelstrup-Hansen, Xuhai Liu, and Geir Helgesen. The strings have a length of 10 to 100 μm and a thickness of about 5 μm, corresponding to the thickness of a few particles. Since the particle fraction is an order of magnitude lower than the percolation threshold and makes the material transparent it can be UV-cured, thus locking the particles into place. The composites can subsequently be deflected resulting in a reversible piezoresistive effect. The obtained gauge factor of 50 is comparable to that of piezoresistive silicon cantilevers.