Two generic record-permutation bubble devices-the bubble ladder and the bubble string comparator-have been reported in the literature but not yet implemented. The former relies on the extensive use of external control lines, while the latter relies solely on the interaction between bubbles. The ladder has evolved into an odd-even sorter and then a rebound sorter, but, unfortunately, it is operated by a large number of control lines. This paper shows that equally efficient but more versatile sorters can be constructed from the bubble string comparators without the control lines. Moreover, the new sorter-an up-down sorter-will be implemented in the recently invented high-density, high-speed, coil-less perforated-sheet bubble devices. Copyright © 1981 by The Institute of Electrical and Electronics Engineers, Inc.