Micrometer-sized integrated plasmonic–electroacoustic hybrid transducer for biosensing applications

This paper presents the development of an on-chip, micrometer-sized, dual-mode transducing device for biosensing applications. The device integrates two distinct transducing mechanisms: plasmonic transduction based on Au nanoparticles and electro-acoustic transduction based on a film bulk acoustic resonator (FBAR). The device has been fabricated by synthesizing Au nanoislands via thermal dewetting on the top electrode of an AlN-based solidly mounted resonator–FBAR on a Si substrate. The fabrication of the hybrid device employs microelectro-mechanical systems (MEMS)-compatible processes that have been optimized to ensure both structural integrity and optimal electrical and optical responses. The device’s ability to detect protein films through electro-acoustic and plasmonic transduction mechanisms is demonstrated by measuring spectral shifts of the electro-acoustic and optical resonances of the device. These shifts are comparable to those of high-performance independent (non-hybrid) optical and electro-acoustic sensors, while offering the benefits of a combined transducing approach, such as the ability to simultaneously measure several independent physical parameters and to provide cross-validation and a reference point. Its compact size and compatibility with MEMS technology make the presented device highly suitable for mass-produced sensor arrays on chips for multiplexed detection in advanced biosensing monitoring.