Omkar A. Nafday

Toward conductive traces: Dip Pen Nanolithography® of silver nanoparticle-based inks

Low cost, direct writing of conductive traces is highly desired for applications in nanoelectronics, photonics, circuit repair, flexible electronics, and nanoparticle-based gas detection. The unique ability of Dip Pen Nanolithography (DPN®) to direct write a variety of materials onto suitable surfaces with nanoscale resolution and area-specific patterning is leveraged in this work. We present a direct-write approach toward creating traces with commercially available silver nanoparticle (AgNP)-based inks using DPN. In this work we demonstrate submicron AgNP feature creation together with a discussion on the ink transport mechanism.

Evidence of meniscus interface transport in dip-pen nanolithography: An annular diffusion model

Ring shaped dots were patterned with mercaptohexadecanoic acid ink by dip-pen nanolithography. These dots have an ink-free inner core surrounded by an inked annular region, making them different from the filled dots usually obtained. This suggests a different transport mechanism than the current hypothesis of bulk water meniscus transport. A meniscus interface ink transport model is proposed, and its general applicability is demonstrated by predicting the patterned dot radii of chemically diverse inks.

Site-specific dual ink dip pen nanolithography™

The ability to deposit different materials with nanoscale precision at user-specified locations is a very important attribute of dip pen nanolithography (DPN). However, the potential of DPN goes beyond simple deposition since DPN used in conjunction with lateral force microscopy (LFM) allows site-specific investigations of nanoscale properties. In this work, we use two different inks, 16-mercaptohexadecanoic acid (MHA) and 1-octadecanethiol (ODT) to show site-specific dual ink DPN enabled exclusively by our proprietary software. A diamond-dot pattern was created by using a layer-to-layer alignment (LLA) algorithm, which enables a MHA pattern (diamond) to be written concentric with another ODT (central dot) pattern. This simple demonstration of multi-ink DPN is not specific to alkanethiol ink systems, but is also applicable to other multi-material patterning, interaction, and exchange studies.

Feature size dependence on hysteresis due to relative humidity ramping and patterning order in dip-pen nanolithography

The water meniscus that forms between an atomic force microscope (AFM) tip and the substrate has been shown to have variable height and width due to relative humidity (RH) hysteresis. The current study investigates the effect of this variability in meniscus shape due to RH on the feature size of patterns written with mercaptohexadecanoic acid on a gold substrate, using dip-pen nanolithography (DPN). The patterns were written under conditions of increasing and decreasing RH cycles with different tip dwell times. The variation in resulting dot sizes during the RH ramping (up and down) cycles was then measured. DPN patterning was also performed with increasing and decreasing order of dwell times at constant RH, in order to quantify whether the order of patterning has an effect on feature size. Significant differences were observed in dot areas patterned over many RH ramping cycles; whereas the order of patterning was observed to have an effect only for dwell times ≤5 s.

Inducing Nanoscale Morphology Changes of Pentaerythritol Tetranitrate Using a Heated Atomic Force Microscope Cantilever

Controlling the morphology of pentaerythritol tetranitrate (PETN) is an important aspect in the nanodetonics research area. Detonation properties are highly dependent on surface area and morphology of PETN. For the first time we show that changes in morphology can be modified at the nanoscale by using a heated atomic force microscope (AFM) cantilever. At temperatures of ∼ 65°C, faceting of PETN islands is observed, whereas at higher temperatures (∼ 124°C) the height of the islands decrease by an order of magnitude.

Site-specific dual ink dip pen nanolithography

The ability to deposit two different materials with nanoscale precision at user specified locations is a very important attribute of dip pen nanolithography (DPN). However, the potential of DPN goes beyond simple deposition since DPN used in conjunction with lateral force microscopy (LFM) allows site-specific investigations of nanoscale properties. In this work, we use two different inks, 16-Mercaptohexadecanoic acid (MHA) and 1-octadenethiol (ODT) to show sitespecific dual ink DPN enabled exclusively by our proprietary software. A diamond-dot pattern was created by using a layer-to-layer alignment (LLA) algorithm which enables the MHA (diamond) to be written concentric with the ODT (central dot) pattern. This simple demonstration of multi-ink DPN is not specific to alkanethiol ink systems, but is also applicable to other multi-material patterning, interaction and exchange studies.

Modeling nanoscale ink transport in Dip Pen Nanolithography

In Dip Pen Nanolithography® (DPN®), ink transport is reported to occur through the water meniscus formed between the AFM tip and the substrate by capillary condensation. It is imperative to understand the ink transport mechanisms in order to develop reliable commercial applications of DPN, and NanoInk is at the forefront of these efforts. In this work, we model the dot patterns of 16-Mercaptohexadecanoic acid (MHA) created by evaporative coating of a 1D 18 cantilever array and perform predictive modeling with solution based MHA cantilever inking results. We extend the functionality of the NanoInk 2D nano PrintArrayTM (2D array) by measuring the uniformity of 1-octadenethiol (ODT) dot patterns created. Further, we try to quantify the uniformity of patterns created by the 2D array, in a more statistically quantitative way. We do this by measuring the dot diameters of over 200 ODT ink patterns over a 1x1cm2 area and examining the uniformity of the ODT vapor inking protocol developed.