Nanofountain probe

A nanofountain probe (NFP) is a device for 'drawing' micropatterns of liquid chemicals at extremely small resolution. An NFP contains 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.

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 rate of deposition 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.

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.

NFP is used in the development of a to scale, 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 (increase rate of reaction), 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 making (fabrication)

• Catalysts for carbon nanotube growth in nanodevice fabrication

• Thiols for directed self-assembly of nanostructures.

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.

• Nanolithography