Microscale 3D printed patterns for nanoscale particle assembly

Directed particle assembly has broad applications in sensors, actuators, microelectronics, robotics, and the biomedical area. Currently available methods include external fields such as electrical or magnetic fields, surface treatment on substrates, and DNA-assisted templates. However, these methods are most efficient at the nanoscale and would lose their efficiency and scalability above microscales. We reported in this research the uses of the 3D printed surface to direct the assembly of nanoparticles. We used carbon nanofibers (CNFs) as an example to show the long-range orders after dipping the 3D printed substrates in CNFs suspensions. The anchoring of CNFs at the solid-liquid-air contact lines will initiate the assembly procedure and further induced the neighboring CNFs because of the van der Waals forces. As a result, the CNFs formed well-regulated bands with controlled spacing and close-packing. These assembled CNFs were demonstrated in sensing applications. A gauge factor regulated the methanol at different concentrations and temperatures to pass the sensor, with the device resistivity change. In this way, the sensitivity as a function of analyte concentration and temperatures was obtained. This research studied nanoparticles' microscale assembly based on a simple 3D printing surface and shed light on a new hybrid manufacturing for nanoparticle assembly.