Fig. 1: Setup and principle of ESM.

a Schematic of the optical setup, where the evanescent field is created by total internal reflection and scattering of the evanescent waves by a particle or protein (E_s) and by the glass surface (E_b) is collected from the top to form an ESM image. b Raw ESM images of a bare cover glass. The blue dashed frame indicates the field of view determined by the illumination area. Incident wavelength: 450 nm. Incident intensity: 60 kW cm⁻². Camera exposure time: 5 ms. c, d, ESM images before and after the binding of a 143.6 nm (c) and 27.9 nm (d) polystyrene nanoparticle (PSNP), and the corresponding differential images. Individual particles are marked with arrows. Incident wavelength: 450 nm. Incident intensity and camera exposure time are 2 kW cm⁻² and 0.2 ms for 143.6 nm, and 60 kW cm⁻² and 1 ms for 27.9 nm, respectively. e ESM image intensity versus particle diameter. The image intensity for each diameter was obtained from the mean value of the corresponding histogram in Supplementary Fig. 5, and normalized with an incident intensity of 60 kW cm⁻² and camera exposure time of 5 ms. f ESM images of 143.6 nm PSNP achieved with different incident wavelengths. Incident intensity: 2 kW cm⁻². Camera exposure time: 0.2 ms. g ESM image intensity of the nanoparticle with an effective diameter of 100 nm versus incident wavelength. The image intensity was achieved from the calibration curve as shown in Supplementary Fig. 5 and 8, and normalized with an incident intensity of 60 kW cm⁻² and camera exposure time of 5 ms. The experiments were repeated three times with similar results for (b–g).