Resonant inertial mass sensing for VOCs: CMOS-compatible SoC integration advantages and challenges: A review

Volatile organic compounds (VOCs) have gained the biomedical community attention given their relevance in exhaled human breath analysis for non-invasive disease diagnosis. Today, only bulky, expensive and high-skill bench-top equipment is commercially available to reach the outstanding resolution and selectivity required for their detection. However, these solutions fail to meet the society demands of portable and low-cost devices required for point-of-care diagnosis and e-health. In this line, resonant inertial mass sensing has emerged as a promising technique to achieve high-resolution VOCs identification, fulfilling the portability requirements. Their excellent distributed mass sensitivity and integration capabilities within standard CMOS microfabrication techniques constitute excellent candidates for building Lab-on-Chip applications in line with current technological trends. The capability of operating as self-sustained oscillators provides an inherent real-time tracking system with quasi-digital output. Resonator coating using novel sensing films for specific analyte caption is required to boost the mass loading effect and improve sensing selectivity. This paper reviews and analyzes resonator topologies proposed in the literature together with the techniques used for the electromechanical transduction, as well as coating materials and procedures. The ultimate goal is to discuss the advantages achieved for CMOS fully integrated solutions, analyzing the state-of-the-art in the field, providing specific design guidelines while foreseeing upcoming trends.