POLYMER PEN LITHOGRAPHY FOR BIOACTIVE SURFACE FUNCTIONALIZATION

Polymer Pen Lithography (PPL) which is a hybrid of Dip-Pen Nanolithography (DPN) and soft lithography technique namely Microcontact Printing (µCP) has been tested for its pros and cons in patterning functional phospholipids under varying instances using high resolution characterization techniques. Although, having the advantage of simultaneously printing at several points of the substrate covering area on the order of millimeter by employing a Polydimethylsiloxane (PDMS) stamp however PPL is yet to make a mark to prove its ability to have as high a feature size compactness and precision in comparison to cantilever based scanning probe lithography techniques such as its parent technique DPN. The detailed analysis reveals a theoretically expected result of phospholipid layers stacked over the base Self Assembled Monolayer (SAM) of the phospholipid which is a direct result of adsorption of the Phosphate head over the hydrophilic glass or Silicon Dioxide substrate which assembles the monolayer constituting the hydrophilic head and hydrophobic tail in a regularly arranged manner. A statistical method is proposed which not only quantifies the stacked phospholipid layers in water, mimicking its natural state being the main constituent of cell membrane in blood plasma, but also has the potential to quantify the Scanning Probe Microscopy (SPM) probe which is used to characterize the sample such that the probe can be said to have certain factor which represent the destruction caused to the particular phospholipid feature while traversing over the sample in water. Moreover, the net overall charge of the phospholipid is observed to affect the topographic image due to the nature of characterization method used therefore a printing methodology to enhance the contrast is proposed to achieve optimum and reliable results. Finally, the difference between the feature is observed in different operating regimes based on the deformation and hence the contact area of the PDMS stamp which is observed to dictate the characteristics of the deposited feature. Most importantly, ink such as DOPE lipid which have not been observed to deposit with DPN due to viscosity were seen to deposit with the employment of PPL as it has partial µCP nature.