The Biro brothers returned to their laboratory and devised a new design, which relied on "capillsry action" rather than gravity to feed the ink. The rough "ball" at the end of the pen acted like a metal sponge, and with this improvement ink could flow more smoothly to the ball, and the pen could be held at a slant rather than straight up. One year later, the Biros were selling their new, improved ballpoint pen throughout Argentina. But it still was not a smashing success, and the men ran out of money.