Abstract
Electrical conductivity is a critical biomarker for cellular activity and a fundamental parameter in material science. However, achieving label-free, contact-free conductivity measurements with optical-scale resolution remains a challenge. Here, we introduce a magneto-photoacoustic coupling effect that enables conductivity mapping through photoacoustic excitation in the presence of a static magnetic field. The governing equation for this phenomenon is derived, demonstrating a linear relationship between the induced photoacoustic pressure and the product of the local magnetic flux density squared and electrical conductivity. This theoretical framework is further validated using numerical simulation, which showcases the method's capability for optical-resolution conductivity imaging. The proposed approach unlocks new opportunities for applications ranging from real-time tracking of neuronal ion channel dynamics to nanoscale defect characterization in metallic and semiconductor materials.