Simple yet Fine: Highly Uniform Sub-microscale Patterned Slippery Liquid-like Surfaces and Bioarrays via Ammonia-Assisted Transfer Printing

Slippery surfaces with covalently attached liquid-like polymer brushes have gained increasing research attention as unique liquid-repellent surfaces with dynamic omniphobic properties and excellent biofouling resistance. However, ultrafine patterning of such surfaces has yet to be explored in a straightforward manner. This work reports a facile polydimethylsiloxane (PDMS) stamp-based transfer printing approach to generate highly uniform patterns with submicrometer sizes on slippery liquid-like surfaces over large areas. The microprism-shaped PDMS stamp soaked with concentrated ammonia solution is pressed onto a slippery substrate modified with linear PDMS brushes, leaving uniform line arrays with widths of ∼500 nm and heights of ∼50-100 nm. The patterning process is investigated in detail to elucidate the properties of the patterned structures and the effect of patterning conditions including the alkali treatment, contact time, pressure, environmental temperature, etc. The volatile ammonia is verified as essential to promote the transfer of silica-like/silicone residues from the stamp, leading to discontinuous nanodot or continuous nanoline features, depending on the amount of transferred silicone to allow the capillary assembly. Furthermore, the patterned PDMS brush surface provides a versatile platform for facile production of biomicroarrays, in which the generated pattern arrays are found to immobilize proteins selectively while the background contamination is minimized by the liquid-like antifouling coating. These results illustrate the application potential of the well-defined patterned slippery surfaces in a wide variety of fields including smart surfaces, biochips, and biosensors, as well as micro-/nanoscale optoelectronic devices.