A diffusive ink transport model for lipid dip-pen nanolithography

Abstract

Despite diverse applications, phospholipid membrane stacks generated by dip-pen nanolithography (DPN) still lack a thorough and systematic characterization that elucidates the whole ink transport process from writing to surface spreading, with the aim of better controlling the resulting feature size and resolution. We report a quantitative analysis and modeling of the dependence of lipid DPN features (area, height and volume) on dwell time and relative humidity. The ink flow rate increases with humidity in agreement with meniscus size growth, determining the overall feature size. The observed time dependence indicates the existence of a balance between surface spreading and the ink flow rate that promotes differences in concentration at the meniscus/substrate interface. Feature shape is controlled by the substrate surface energy. The results are analyzed within a modified model for the ink transport of diffusive inks. At any humidity the dependence of the area spread on the dwell time shows two diffusion regimes: at short dwell times growth is controlled by meniscus diffusion while at long dwell times surface diffusion governs the process. The critical point for the switch of regime depends on the humidity.

Development of Dip‐Pen Nanolithography (DPN) and Its Derivatives

“…In the DPN of phospholipids, also known as lipid‐DPN (L‐DPN), amphiphilic lipid molecules are written and self‐assemble into ordered stacks of membranes . By virtue of the layered self‐assembly of the molecules which also includes surface diffusion in the process, yet a more liquid ink like bulk transition of material at the same time, this ink combines aspects of both ink regimes discussed above …”

Phospholipid arrays on porous polymer coatings generated by micro-contact spotting

“…In the present approach, the pores of the HEMA-EDMA support act as a mesh that contains lipid ink in a confined space, providing high pattern definition, and presenting more binding sites than would be available on a flat substrate [10]. The main phospholipid component in our ink mixture is 1,2-dioleoyl- sn -glycero-3-phosphocholine (DOPC, T m = −16.5 °C) which allowed for the control of ink fluidity under humidity controlled conditions [11–12]. Using quill-like pens (SPTs, short for surface patterning tool [13]) for lipid ink deposition permitted the reduction of the volume of phospholipids needed for array generation, as compared to other spotting techniques like ink jet printing, without decrease in the quality of the array or reduction of binding sites for analyte molecules.…”

Click-Chemistry Based Allergen Arrays Generated by Polymer Pen Lithography for Mast Cell Activation Studies

“…Existing platforms for mast cell activation profiling based on dip‐pen nanolithography (DPN) with phospholipids (L‐DPN) have been shown to be effective tools for research on the mast cell activation process and its moderation by glucocorticosteroids . However, for cellular activation profiling to become a standard tool in biomedical research or in clinical settings, sample stability issues and the relative ease of use must be addressed.…”

“…[ 3 ] Furthermore, the study of allergic cellular responses on patterned surfaces can yield novel insights into the mechanism governing the activation process itself, and consequently improve the development of novel treatment options. [ 4,5 ] Existing platforms for mast cell activation profi ling based on dip-pen nanolithography (DPN) with phospholipids (L-DPN) [ 6,7 ] have been shown to be effective tools for research on the mast cell activation process and its moderation by glucocorticosteroids. [ 8,9 ] However, for cellular activation profi ling to become a standard tool in biomedical research or in clinical settings, sample stability issues and the relative ease of use must be addressed.…”