a Schematics of the InSMAR-chip (left panel) and the cross-section view of the chip (right panel). b Photograph of an InSMAR-chip with a droplet array in the microwells. The contact angle of the superhydrophobic surface is >160°. c Photographs of the droplets in the microwells. (Top) The droplet array of culture medium formed spontaneously when the excess medium was aspirated out from the chip. (Middle) The droplet array of the Matrigel loaded into the microwells with an electronic pipette. (Bottom) The Matrigel droplets are overlaid with the culture medium by the spot-cover method. d Schematics of the reagent delivery methods on the InSMAR-chip: the submerge-aspirate method and the spot-cover method. e Images of LC96-O cultured on the InSMAR-chip (on-chip) and in the conventional microplate (off-chip), showing the continuous growths of LCOs in both conditions from days 0 to 14. Scale bar, 200 µm. The experiments are repeated three times. f Bright-field images of LC141-O at day 7 and fluorescent images showing the viability of organoids (green: live cells; red: dead cells). Scale bar, 200 µm. The experiments are repeated three times. g, h Comparison of the growth rates (g) and the viabilities (h) in four organoid lines indicating no significant difference between the LCOs cultured on-chip and off-chip (n = 20 biologically independent cells. Data are presented as mean ± SD). i H&E stain of the parental tumor tissue and the corresponding LCOs cultured on the InSMAR-chip and in the conventional multiwell plate. Scale bar: 20 µm. The experiments are repeated three times.