<p>This study utilizes the nonlocal strain gradient elasticity theory to investigate the dimensionless frequency shift caused by adsorption in a dynamic resonator system. The system consists of double functionally graded porous sandwich microbeams with a two-dimensional periodic square holes network, connected through an elastic medium and influenced by a magnetic field, compressive loading, and distributed water molecules. The double functional microbeams follow a power-law distribution for thickness-dependent properties, considering two porosity patterns. The impact of the applied magnetic field is analyzed using Maxwell’s equations. Nonlocal strain gradient elasticity theory is employed to capture small-scale effects. Both Euler–Bernoulli and Rayleigh beam theories are utilized to account for bending and rotary inertia effects. Interatomic interaction energies are modeled using Lennard–Jones (6–12), Morse, and Buckingham potentials, while perforation effects are incorporated into the equivalent bending stiffness. Analytical solutions are derived using the Navier-type method, and numerical solutions via the differential quadrature method. Results indicate that the dimensionless frequency shift is strongly influenced by porosity volume fraction and hole configuration. Water molecule adsorption reduces the frequency shift, while increases in magnetic field intensity and length-to-width ratio improve structural sensitivity. Additionally, both dimensionless compressive force and spring parameter introduce a softening effect, lowering system stiffness and amplifying the drop in dimensionless nonlocal frequency. A clear discrepancy between Euler–Bernoulli and Rayleigh model predictions highlights the role of rotary inertia. This model offers a comprehensive framework for designing advanced microresonators for nano/microscale sensing applications, such as mass detection and virus-induced frequency modulation.</p>