Sticking a business card to a ceiling needs no glue, no magnet and no vacuum pump. A small vibration motor and a thin layer of air are enough. Bolt a coin-cell eccentric rotating mass (ERM) motor to a card, hold it a fraction of a millimetre beneath a flat ceiling, and it stays there. The card is not held up by force pressing against the ceiling. It is pulled up by the air in the gap. The mechanism is squeeze-film flow: - The motor drives the card up and down by tens of micrometres at roughly 100 to 250 Hz. - On each closing stroke, air is forced radially out of the narrowing gap. On each opening stroke, it is drawn back in. - Because the gap is thin compared with the card’s width, the radial velocity is large. Bernoulli’s principle says fast-moving air has low static pressure. - Dynamic pressure scales as one half of rho times v squared. It is always positive, whichever way the air flows. So the pressure deficit in the gap does not cancel over a cycle. It averages to a net suction....