Printing nanoparticles from the liquid and gas phases using nanoxerography

Abstract

This paper reports on the directed self-assembly of nanoparticles onto charged surface areas with a resolution of 200 nm from the liquid phase and 100 nm from the gas phase. The charged areas required for this type of nanoxerographic printing were fabricated using a parallel method that employs a flexible, electrically conductive, electrode to charge a thin-film electret. As electrodes, we used metal-coated polymeric stamps and 10 µm thick doped silicon wafers carrying a pattern in topography. Each electrode was brought in contact with a thin-film electret on an n-doped silicon substrate. The charge pattern was transferred into the thin-film electret by applying a voltage pulse between the conductive electrode and the silicon substrate. Areas as large as 1 cm 2 were patterned with charge with 100 nm scale resolution in 10 s. These charge patterns attract nanoparticles. A liquid-phase assembly process where electrostatic forces compete with disordering forces due to ultrasonication has been developed to assemble nanoparticles onto charged based receptors in 10 s from a liquid suspension. A gas-phase assembly process was developed that uses a transparent particle assembly module to direct particles towards the charged surface while monitoring the total charge of assembled particles. Nanoparticles were generated using a tube furnace by evaporation and condensation at the outlet. The electrostatically directed assembly of 10-100 nm sized metal (gold, silver) and 30 nm sized carbon particles was accomplished with a resolution 500-1000 times greater than the resolution of existing xerographic printers.

Micro- and Nano-assembly and Manipulation Techniques for MEMS

“…Krinke et al (2001) demonstrated 100-nm patterns of gold particles deposited from a gas phase onto a silicon dioxide substrate. Barry et al (2003) developed PDMS stamps to be used as electrodes for electrifying patterns onto PMMA substrates. Recently, Naujoks and Stemmer (2004) demonstrated that a xerography-like process allows the direct fabrication of sub-micron spots of bio-molecules from an insulating oil phase .…”

Gas Phase Nanoparticle Integration

“…A number of concepts have been developed to print nanoparticles directly from powder and solution. Sub -one micrometer resolution assembly has been accomplished using charge directed nanoxerographic printing [1,2] and topographically directed assembly incorporating both capillary and electrostatic forces [3,4]. While the solution methods have emerged, directed self-assembly processes from the gas phase are not widely available but immensely important.…”

“…The nanomaterial building blocks would not have to be transferred in solution as is currently the case. Solution concepts have their own set of problems -almost all of the reviewed receptor based assembly concepts [1,2,[5][6][7][8][9][10][11][12][13] require surface functionization to prevent agglomeration or to guide the assembly which often interferes with the electronic or optical properties. Direct integration from the gas phase would support the use of well established passivation concepts to create high quality nanomaterial building blocks that maintain the electronic and optoelectronic functionality.…”

Charging Process and Coulomb-Force-Directed Printing of Nanoparticles with Sub-100-nm Lateral Resolution

“…22 In our own research we have developed a parallel charge patterning process enabling nanoxerographic printing. [12][13][14][15] Patterning of charge with 100-200 nm resolution and transfer of 50 nm to 20 µm sized particles including silver, gold, indium, iron oxide, graphitized carbon, iron beads, and Xerox toner from a powder, gas, and liquid phase [12][13][14][15] has been accomplished. …”

“…[12][13][14][15][16][17][18]25,27 In recent years there has been an increased focus on the use of long range electrostatic forces to direct the assembly of nanomaterials since it can potentially be used to assemble a vast variety of materials (magnetic, nonmagnetic, insulating, semiconducting, conducting, organic, and inorganic materials) without altering the surface chemistry of the materials. [12][13][14][15][16][17][18]25,27 Electrostatic forces are sufficiently long range to attract nanomaterials from the gas and liquid phases. The other advantage is that global fields can be applied using electrical electrodes to program the assembly.…”