1932-4510/15©2015IEEE JUNE 2015 | IEEE NANOTECHNOLOGY MAGAZINE | 11 S ZHENG H. ZHU Piezoresistive Strain Sensors Based on Carbon Nanotube Networks SINCE THEY WERE DISCOVERED in 1991 [2], CARBON nanotubes (CNTs) have attracted enormous atten- tion because of their remarkable properties [1], such as high electrical conductivity, ultrasmall diameter, and large aspect ratio. In addition, CNTs exhibit significant electromechanical properties [3] that could be useful in applications for piezore- sistive-type sensors such as strain gauges, pressure sensors, chemical and biological sensors, microelectronic devices, and struc- tural condition monitoring through strain sensing [4]. In addition to the application of a single CNT in various nanoelectro- mechanical applications, CNT researchers have gradually moved toward potential applications of CNTs as filler candidates in various types of multifunctional material systems, representing a new direction with broad applications [5], [6]. Digital Object Identifier 10.1109/MNANO.2015.2409412 Date of publication: 10 April 2015 Contemporary approaches related to electrical conductivity. ARROWS LICENSED BY GRAPHIC STOCK