Rapid spheroid clearing on a microfluidic chip

. Repetitive cycling of the pH induces an osmotic flow within the hydrogel-embedded spheroid. Thirty cycles, performed in a total time interval of 10 minutes on-chip, reduced the clearing time of a hydrogel-embedded spheroid (with a diameter of 200 μm) from 14 days to 5 hours. Therefore, we developed a physicochemical method to decrease the clearing time of hydrogel-embedded tissues. While the osmotic pump mechanism is an alternative to electrophoretic forces for decreasing tissue clearing times, the integration of the CLARITY method on chip could enable high throughput imaging with 3D tissue cultures.