Inkjet printing of patterned ultra-slippery surfaces for planar droplet manipulation

We propose a facile, inexpensive and scalable inkjet-printing method to fabricate patterned lubricant-infused surfaces as the ultra-slippery platform for surface microfluidics, and demonstrate typical planar droplet manipulations. Micrometer patterns were printed on scotch tapes by a home-use inkjet printer to form a template with patterned adhesion contrast. Closely packed monolayer of microbeads was assembled driven by the water surface tension and selectively adhered on the unprinted tape. Then poly(dimethylsiloxane) (PDMS) was cast against the microbead template to form a bowl-like surface, and ultra-slippery PDMS surface was achieved after spin coating lubricant oil. Its interface characterization, sliding performances and long-time stability which are critical for surface microfluidic applications were evaluated and analyzed. Finally the patterned ultra-slippery PDMS was employed as the surface microfluidic platform, and droplet transportation, mixing, trapping and releasing functions have been enabled by very simple and facile driving methods such as pneumatic and gravity driving, which pave a new way for potential flexible and low-cost applications of surface microfluidics.