Recently, the printing of electronics has received increased attention because of its merits of low cost, low material consumption, high scalability, high throughput, and additive manufacturing. Commonly used printing techniques such as inkjet printing and screen printing have limited scalability and resolution (micro or sub-micro scale). Directed assembly-based printing, on the other hand, is scalable and can realize the high resolution of tens of nanometers. However, directed assembly processes, such as electric field-directed assembly and fluidic flow-driven assembly, either require the conductive substrate to generate electric field or lack versatility, scalability, or throughput, which limits their practical applications. 
Technology Overview
In this invention, Northeastern University researchers developed a novel, directed assembly-based printing technique utilizing interfacial convective assembly to rapidly assemble particles in micro/nanoscale patterns on any substrates. In the interfacial convective assembly, a patterned substrate is initially sonicated in isopropanol (IPA) using a bath type sonicator for a few seconds. After sonication, the substrate is removed from the IPA bath, leaving a thin IPA film on the substrate. Then, a glass slide is covered on the suspension, creating a confined environment with the substrate. Due to the convective flow, particles are carried towards the patterned substrate and then trapped in the pattern areas via van der Waals interactions as well as geometrical confinement. At the end of the assembly, the substrate is tilted perpendicular to the ground to remove excess particles from the non-patterned hydrophobic surface through stokes drag exerted by the liquid meniscus at the three-phase contact line.
- Assembly can be conducted on any substrate (both conductive and non-conductive and both hydrophilic and hydrophobic)
- The interfacial convective assembly takes place over the entire substrate at the same time instead of only at the suspension-substrate interface for the case of the conventional convective assembly
- The solutal Marangoni convection has a high flow velocity in the meter per second scale. The high-velocity flow drives particles to circulate rapidly in the suspension, enabling the particles to be assembled in the hydrophilic patterns within a few minutes 
- The fabricated silver nanorods show a single crystal structure with a low resistivity of 8.58 × 10-5 Ω cm
- Because of high conductivity, the printed single crystal silver nanowires and nanorods have great potential to be used as two-dimensional and three-dimensional interconnect for integrated circuits
- The silver nanorod array has the potential to be used as plasmonic nanostructures for optical device applications
- The printed nanoparticle patterns can be used in bio/chemical sensors because of their high surface area
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Patent Information:
For Information, Contact:
Mark Saulich
Associate Director of Commercialization
Northeastern University
Zhimin Chai
Adnan Korkmaz
Cihan Yilmaz
Ahmed Busnaina
3D printing