Optofluidic SERS chip with plasmonic nanoprobes self-aligned along microfluidic channels

This work reports an optofluidic SERS chip with plasmonic nanoprobes self-aligned along microfluidic channels. Plasmonic nanoprobes with rich electromagnetic hot spots are selectively patterned along PDMS microfluidic channels by using a Scotch tape removal and oxygen plasma treatment, which also provide the permanent bonding between PDMS and a glass substrate. A silver film with an initial thickness of 30 nm after oxygen plasma treatment creates nanotips and nanodots with a maximum SERS performance, which were successfully implanted with microfluidic concentration gradient generators. The novel device enables the label-free and solution-phase SERS detection of small molecules with low Raman activity such as dopamine at micromolar level in flow. This optofluidic SERS chip can be readily expanded for microfluidic networks with diverse functions for advanced optical biochemical assays.