Microfabrication of an Integrated Magneto-Capacitive Biosensor for Label-Free Biomarker Detection

We report the development of a novel microfabricated biosensor platform that seamlessly integrates magnetic manipulation with direct-field capacitive sensing (DF-CS) within a microfluidic system, enabling label-free and highly sensitive biomarker detection. Guided by comprehensive 3D multiphysics simulations, we optimized design parameters to maximize magnetic field gradients, enhance fluid dynamics for efficient nanoparticle transport, and increase capacitive detection sensitivity. The device features microfabricated planar coils that generate controlled magnetic fields to capture and concentrate functionalized magnetic nanoparticles (MNPs) conjugated with biomarker-specific antibodies at predefined sensing sites. This localized MNP accumulation alters the dielectric properties of the medium, which is precisely detected by capacitive electrodes embedded within the microfluidic channels. Experimental validation demonstrates significant environmental responsiveness, with capacitance values increasing by 17.6% to 25.5% upon exposure to deionized water, affirming the platform's dielectric sensitivity crucial for biosensing applications. Magnetic trapping experiments reveal rapid and efficient MNP capture, achieving steady-state accumulation within two minutes, and enabling reversible release upon magnetic field deactivation for repeatable dynamic assays. The biosensor exhibits high reproducibility, structural integrity, and consistent sensitivity across various planar coil configurations, underscoring its suitability for integration into wearable and portable diagnostic devices. By eliminating the need for complex surface chemistries or labeling procedures, this integrated magneto-capacitive platform provides a scalable and versatile solution for continuous health monitoring. PACS: 0000, 1111 2000 MSC: 0000, 1111