As much as buttons are an effective way to provide users with clear controls for their electronics, they aren't the most humanizing approach to industrial design. The Gerhardt Kellermann Fan proposes a system of commands that invites a much more natural action of the fingertips, requiring a soft stroke to alter the gadget's operation.
The base of the ventilator is a smooth and switch-free circle across which one must sweep his hand to change the speed of the spinning blades. It isn't clear how sensitive this device might be, or the exact quality of the touch that might influence the desired effect. Perhaps the Gerhardt Kellermann Fan increases its rate with every brush, or maybe a faster stroke initiates quicker revolutions.
The Gerhardt Kellermann Fan Changes Speed with a Gentle Stroke
Amelia Roblin — July 3, 2012 — Art & Design
References: gerhardtkellermann & notcot.org