A Generalizable Single-Chip Calibration Method for Highly Quantitative SERS via Inkjet Dispense

We present a calibration method for quantitative surface-enhanced Raman scattering (SERS) on a single-chip based on inkjet dispense (ID-SERS). We exploit the ability of inkjet to precisely pattern microdroplets at high resolution to encode multiple standard curves on the surface of a single 1 mm² SERS substrate. We demonstrate quantitative SERS measurements with a relative standard error (RSE) below 3% for aqueous solutions of 1,2-bis(4-pyridyl)ethylene (BPE), the lowest reported to date. Most importantly, the RSE scales with patterning density and sensor size, showing the potential for even higher measurement accuracy. This calibration technique can be generalized to other plasmonic substrates and offers several additional advantages including speed (subsecond drop-and-dry), low sample volumes (<1 nL), and automation. Finally, we investigate factors impacting the limit of detection of this approach and demonstrate a 30-fold enhancement of sensitivity via layered inkjet dispense. We believe that ID-SERS paves the way for the development of reproducible plasmonic sensing for real-world quantitative applications.