Nanofountain probe

Nanofountain probe (NFP) is a cantilevered micro-fluidic device terminated in a nanofountain. The embedded microfluidics facilitates rapid and continuous delivery of molecules from the on-chip reservoirs to the fountain tip. When the tip is brought into contact with the substrate, a liquid meniscus forms, providing a path for molecular transport to the substrate. By controlling the geometry of the meniscus through hold time and deposition speed, various inks and biomolecules could be patterned on a surface, with sub 100 nm resolution.

Optical image of an array (left) and SEM image of the tip (right)

Historical background

The advent of dip-pen nanolithography (DPN) in recent years represented a revolution in nanoscale patterning technology. With sub-100-nanometer resolution and an architecture conducive to massive parallelization, DPN is capable of producing large arrays of nanoscale features. As such, conventional DPN and other probe-based techniques are generally limited in their deposition rate and by the need for repeated re-inking during extended patterning. To address these challenges, nanofountain probe was developed by Espinosa et al. where microchannels were embedded in AFM probes to transport ink or bio-molecules from reservoirs to substrates, realizing continuous writing at the nanoscale^[1]. Integration of continuous liquid ink feeding within the NFP facilitates more rapid deposition and eliminates the need for repeated dipping, all while preserving the sub-100-nanometer resolution of DPN.

Microfabrication

Nano fountain probes (NFPs) are fabricated on the wafer-scale using microfabrication techniques allowing for batch fabrication of numerous chips^[2]. Through the different generations of devices, design and experimentation improved the device yielding to a robust fabrication process. The highly enhanced feature dimension and shapes is expected to improve the performance in writing and imaging.

Microfabrication sequence

Applications

Direct-write nanopatterning

NFP is used in the development of a scalable, direct-write nanomanufacturing platform. The platform is capable of constructing complex, highly-functional nanoscale devices from a diverse suite of materials (e.g., nanoparticles, catalysts, biomolecules, and chemical solutions)^[3]. Demonstrated nanopatterning capabilities include:

• Biomolecules (proteins, DNA) for biodetection assays or cell adhesion studies

• Functional nanoparticles for drug delivery studies and nanosystems fabrication

• Catalysts for carbon nanotube growth in nanodevice fabrication

• Thiols for directed self-assembly of nanostructures.

Patterning mechanism of NFP through controlled meniscus and several sample patterns

Direct in-vitro single-cell injection

Taking advantage of the unique tip geometry of the NFP nanomaterials are directly injected into live cells with minimal invasiveness^[4]. This enables unique studies of nanoparticle-mediated delivery, as well as cellular pathways and toxicity. Whereas typical in vitro studies are limited to cell populations, these broadly-applicable tools enable multifaceted interrogation at a truly single cell level.

In vitro single cell injection using NFP

References

1. ^ 1. Kim, K.-H., et al. Massively parallel multi-tip nanoscale write with fluidic capabilities-fountain pen nanolithography (FPN). in Proceedings of the 4th International Symposium on MEMS and Nanotechnology. 2003. Charlotte, North Carolina.
2. ^ Moldovan, N., K.-H. Kim, and H.D. Espinosa, Design and fabrication of a novel microfluidic nanoprobe. Journal of Micromechanical Systems, 2006. 15: p. 204-213.
3. ^ Loh, O.Y., et al., Electric field-induced direct delivery of proteins by a nanofountain probe. Proceedings of the National Academy of Sciences of the United States of America, 2008. 105: p. 16438–43.
4. ^ Loh, O., et al., Nanofountain-probe-based high-resolution patterning and single-cell injection of functionalized nanodiamonds. Small, 2009. 5: p. 1667-1674.

See also

• Nanolithography
• Infinitesimal
• Micro and NanoMechanics Laboratory