*Article* **Piezoresistive Characteristics of Nanocarbon Composite Strain Sensor by Its Longitudinal Pattern Design**

**Sung-Yong Kim 1,†, Baek-Gyu Choi 1,†, Gwang-Won Oh 1, Chan-Jung Kim 1, Young-Seok Jung 1, Jin-Seok Jang 2, Kwan-Young Joung 3, Jun-Ho Suh <sup>4</sup> and Inpil Kang 1,\***


**Abstract:** For an engineering feasibility study, we studied a simple design to improve NCSS (nanocarbon composite strain sensor) sensitivity by using its geometric pattern at a macro scale. We fabricated bulk- and grid-type sensors with different filler content weights (wt.%) and different sensor lengths and investigated their sensitivity characteristics. We also proposed a unit gauge factor model of NCSS to find a correlation between sensor length and its sensitivity. NCSS sensitivity was improved proportional to its length incremental ratio and we were able to achieve better linear and consistent data from the grid type than the bulk type one. We conclude that the longer sensor length results in a larger change of resistance due to its piezoresistive unit summation and that sensor geometric pattern design is one of the important issues for axial load and deformation measurement.

**Keywords:** carbon nanotube; strain sensor; piezoresistive mechanism; sensor pattern design
