Figure 1b shows a schematic of THz transmittance measurement through the virus sample dropped sensing chip. The multi-resonance nano-antenna sensing chip was fabricated with two-dimensional punctured rectangular slots with a width of w = 500 nm, lengths of l = 200, 100, 67, and 50 μm, and spacings between adjacent two antennas are 15, 7.5, and 3.75 μm in the horizontal direction, respectively. The second type of nano-antenna sensing chip, used in later measurements, was fabricated with a length of l = 40 um. The periods between slots are 40 um in the horizontal direction and 50 um in the vertical direction. These nano-antennas are patterned in a 150-nm-thick gold on the top of double-side-polished 500-μm-thick silicon wafer using an e-beam lithography technique. The total slot numbers more than 1000 within a whole area of 2 mm × 2 mm are designed to minimize possible errors from a random distribution of protein sample during the liquid drop casting. Each slot has a fundamental resonance (f res); for example, the multi-resonance nano-antenna sensing chip has three resonances at 0.62, 0.93, and 1.31 THz, respectively, and the single-resonance nano-antenna sensing chip has a single fundamental resonance at 1.4 THz according to the effective refractive index of substrate19. For the measurements of virus samples, we dropped 2 uL of virus solution in liquid state and dried it for 1 hour in controlled laboratory atmosphere (30% of relative humidity and 20 degree of Celsius) to avoid any possible signal error from the water absorption at THz frequency20. The dropped virus sample builds a thin film on the multi-resonance sensing chip as shown in the top of Fig. 1c. After 20 minutes of THz field excitation, diffraction pattern appeared in the middle of film as shown in the bottom of Fig. 1c. Without THz field, the pattern disappeared within 5 minutes. Protein aggregation and crystallization effect under high electric field have been reported previously21–23. Even though our case is not exactly matched to the conditions for the reported protein crystallization, such as concentration of protein, precipitants, pH, and temperature of protein solution, it can be assumed that the changed surface is related to the temporal aggregation as a beginning step of protein crystallization under strongly enhanced THz electric field. The further study on this interesting effect of protein aggregation and induced crystallization using nano-antenna assisted THz field is needed, but it will not be discussed here in depth (out of scope of this report).