take one apart and find out?
There is a chimney running up the centre of the juice tank that ends at the drip tip. The chimney is 'sealed" by the wicks. The juice sits in the tank, the wick goes into the tanks and wicks the juice. The juice is turned to vapor by the coil and draws up the chimney. There is a seal on the drip tip to stop any leakage from the tank.
Its a simple yet effective design.
Does that help?