The Effect of Ink Composition and Relative Humidity on Nanoclusters Size on Meta-Chemical Surfaces Using Dip-Pen Nanolithography

Anna Grouzmark, Green Engineering, Sami Shamoon College, Beer Sheva, Israel (annagr1@ac.sce.ac.il)
Ariela Burg, Chemical Engineering, Sami Shamoon College, Beer Sheva, Israel
Moshe Zohar, Electrical And Electronics Engineering, Sami Shamoon College, Beer Sheva, Israel
Dror Shamir, Nuclear Research Centre Negev, Beer Sheva, Israel

Monitoring water sources for heavy-metal contamination is a global priority. Currently, the standard analytical method is Inductively Coupled Plasma (ICP) analysis; however, this technique is costly, non-portable, and thus unsuitable for continuous and on-site monitoring. To overcome these limitations, this study focuses on development of electrochemical nanosensors for detecting heavy metals at ppb concentrations using Dip-Pen Nanolithography (DPN).

The research aims to develop optimized ink formulations, composed of polymers, solvents, and ligands, and to determine the ideal patterning conditions for forming nanoclusters with a high surface-to-volume (S/V) ratio. A high S/V ratio of the clusters, together with an appropriate ligand quantity, is a key factor influencing sensor sensitivity. Four polymers: Polystyrene sulfonate, Vinylphosphonic acid, Polydimethylsiloxane, and Polymethyl methacrylate were examined in combination with the ligands Glutathione, Cupferron, Nitrilotri-Methylphosphonic acid, D-Penicillamine, and 1,8-Diaminonaphthalene.

The ink composition and relative humidity are major factors influencing the size and morphology of the nanoclusters. To investigate the relationship between the rheological properties of the ink, the patterning process was performed under different humidity conditions, in conjunction with flow rate measurements of each ink formulation in the inkwell. It was found that inks with a low flow rate (below 2 mm/s) respond more sensitively to humidity variations and exhibit higher S/V ratio values, (ranging from 200 to 450 µm⁻¹). These results indicate a strong correlation between the rheological properties of the ink, the humidity, and the dimensions of the nanoclusters.