Fall 2010 IAB
September 15 to 17

Plenary 3: Sun Choi

Fast, High-Throughput Micro, Nanoparticle Printing with Tunable Resolution & Size

We report a novel technique to print micro, nanoparticle assembly with tunable resolution (from several micron to hundreds micron) by using porous silicon membrane-based printing head. Creating regular, repetitive and well-defined three-dimensional patterns of particle assembly in targeted area is a major bottleneck in various applications such as the fabrication of three-dimensional photonic crystals, printed electronics on flexible substrates, colloidal quantum-dot based devices for display, plasmonics and etc.
Conventional approaches to print micro, nanoparticles - inkjet printing, roll-to-roll printing, gravure printing, or photo-template assisted evaporative self-assembly are still majorly suffering from numerous constraints such as low-throughput, low resolution, compatibility with various substrates or incapability of large area patterning. In order to reduce processing time and cost for large-scale manufacturing of optical, electronic devices, it is crucial to develop innovative, novel governing platforms to print various kinds of micro, nanoparticles with high speed and throughput.
In this presented work, micro, nanoparticles are printed via porous silicon membrane of a newly designed printing head. The printing head is fabricated by applying conventional micro-fabrication technology to SOI (Silicon-On-Insulator) substrates. Holes of the printing head are defined by photolithography and reactive-ion-etching is followed. Backside is etched by TMAH wet etching in order to define a reservoir region to contain micro, nanoparticle suspension. After the fabrication of a die-size, printing head, this head is attached to a handling wafer and this handling wafer-printing head complex is directly attached to the mask holder of conventional UV-exposure system. Micron-precision, three-axis stage controller of the UV-exposure system enables the printing head to locate the targeted area with accurate alignment. After containing the suspension in the reservoir, direct contact of the head with substrate is performed to transfer multiple micron-size droplets from the bulk suspension the reservoir to the substrate through porous membranes. Rapid-evaporation of these small droplets leads to fast printing of the particles in a high-throughput manner. As a result, printing of silica microparticle, ZnO nanopartcle and Au nanoparticle assembly with various resolution (from 1 Ám to 130 Ám) has been achieved within a few seconds with high-throughput and yield. This result indicates the presented process can be easily extended to large area printing with a capability of multi-layer process.
It is anticipated this technique will be applied to large-scale manufacturing of pre-patterned substrates for SERS (Surface Enhanced Raman Spectroscopy), nanoparticle-based conductometric bio-chem sensors and the circuitry of printed electronics.