Programmable Dielectrophoretic Assembly of Carbon Nanotube Arrays for Multidirectional Strain Sensor

Programmable and precise assembly of low-dimensional nanomaterials is the long-standing bottleneck for fabricating anisotropic flexible electronics, which provides physical support for sensing both strain magnitude and direction, and are critical for soft robotics and human-machine interfaces. However, existing strategies suffer from low alignment efficiency, poor spatial programmability, and complex fabrication. Here, a programmable dielectrophoretic (DEP) assembly methodology is reported, leveraging structured electric fields and serrated electrodes to achieve spatially selective, oriented deposition of carbon nanotubes (CNTs). Through theoretical analysis of the CNTs' motion behavior and impedance testing to quantify alignment degree, the electric field parameters are optimized. Meanwhile, combining with the design of a serrated electrode, the assembly efficiency of CNTs is also significantly improved (<90 s). As a proof-of-concept, the fabricated anisotropic strain sensor exhibits a sensitivity ratio of 16.52 between parallel and perpendicular directions and maintains robust durability over 2000 cycles. To demonstrate the utility of this programmable assembly, the CNTs are configured as a right-angle sensor array, which is capable of detecting the magnitude and direction of strain within the 180° range. This work not only extends the development of dielectrophoresis in the manufacturing of anisotropic composites but also offers new avenues for developing high-performance, multifunctional flexible electronics.