A vacuum-powered model called VORTEX that can climb any smooth surface by employing a household vacuum cleaner motor to hold it to the wall. It works a little like an inverse hovercraft, using a skirt to stop air leakage and a carefully designed rotary turbine to create negative pressure below the unit and keep it stuck to whatever it's climbing. When the robot hits a wall and continues to move forwards, it begins to tilt up. At an angle of about 30-35 degrees, a tilt switch activates and the vacuum motor is switched on, pulling it closer to the wall and allowing the skirt surrounding the rotor to be more effective in creating the negative pressure.