Overcoming Diffusion-Limited Biosensing by Electrothermoplasmonics

Biosensing based on optical micro- and nanoresonators integrated in a microfluidic environment is a promising approach to lab-on-a-chip platforms capable of detecting low concentrations of analytes from small sample volumes. While sensitivity has reached the single molecule level, in practice, the applicability to real-life settings is limited by Brownian diffusion of the analyte to the sensor surface, which dictates the total duration of the sensing assay. Here, we use the electrothermoplasmonic (ETP) effect to overcome this limit through opto-electrical fluid convective flow generation. To this end, we designed a Localized Surface Plasmon Resonance (LSPR) sensing chip that integrates ETP operation into state-of-the-art microfluidics. First, we optimize and characterize the ETP dynamics inside the microfluidic chamber, showing high fluid velocities. Then, we perform proof-of-concept experiments on model immunoglobulin G detection to demonstrate ETP-enhanced biosensing. Our results demonstrate the synergetic effect of temperature and electric field proving that ETP-LSPR has improved performances over standard LSPR.