Wafer‐Scale Deterministic Fabrication of Axis‐Ratio–Engineered Silicon Nanoparticles for On‐Resonance Electric–Magnetic Dipole Interference

ABSTRACT High‐index dielectric nanoparticles support coexisting electric and magnetic dipole resonances whose interference governs directional scattering. Achieving reproducible control of this interference has remained challenging. Here, we report a wafer‐scale top‐down fabrication strategy that yields silicon nanoparticles with exceptional uniformity (coefficient of variation 1.7%–2.4%), enabling deterministic axis‐ratio (AR) tuning as a design parameter. By defining pillar geometry and precisely controlling annealing and oxidation, we tune dipolar mode overlap to realize on‐resonance Kerker‐type forward scattering with a forward‐to‐backward ratio of 12.5, which is among the highest reported for single silicon nanoparticles under comparable substrate‐supported finite‐NA measurement geometries. At the optimized AR = 2.1, this near‐Kerker condition enables ultrasensitive refractometric sensing and label‐free monitoring of protein‐corona formation in serum, achieving a resolution of ~10 ⁻⁴ refractive‐index units per 1% fetal bovine serum (FBS). These results establish AR engineering as a deterministic route to tailor electric–magnetic interference, linking wafer‐scale fabrication precision with single‐particle optical control and quantitative bio‐interfacial sensing.