Ultrasound, Levitation, and Painting
Ultrasound, levitation and painting
Ultrahaptics’ core technology uses ultrasound to create haptic feedback in mid-air, with no need for gloves or hand-held controllers.
To achieve this, the amplitudes and phases of multiple ultrasound waves originating from an array of transducers (ultrasonic speakers) are modulated using patented algorithms. When controlled in this way, the waves constructively interfere and achieve a maximum pressure at a desired location in space, e.g. a user’s fingertip. The pressure is sufficient to generate tactile sensations.
Ultrasound, however, has many other applications, including levitating and controlling small particles. With some amendments to the input algorithms, ultrasound waves can be modulated to destructively interfere and thus achieve a minimum pressure (surrounded by maxima), thus creating a “trap” where a small particle can levitate.
One interesting application that we are exploring within the Levitate project is what we’ve called LeviPaint, where a levitating particle is used as a paint brush.
To achieve this we created a custom-built platform using two ultrasound transducer arrays. They were oriented facing each other by means of a structure made of Lego bricks and separated by a distance of 176 mm. This improves the strength and stability of the ‘trap’ where a small particle can levitate, by ensuring that opposing pressure forces are cancelled.
Figure 1 : Two transducer arrays held facing each other by Lego bricks. The space between them form an levitation space where acoustic traps can levitate small particles and move them around or along trajectories to form Levipaintings.
Next, a small polystyrene particle was placed in the trap and transported along predetermined trajectories defined by simple parametric equations. For example we could make particles move round a circle, or a trefoil path, or even the Ultrahaptics logo.
By taking long exposure photographs (approx. 30 seconds) of the moving levitating particles on dark backgrounds we captured the trails followed by the particle and created the first-ever Levipaintings!
What do you think?
Another visualisation technique that we are exploring is that of Schlieren photography .
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Figure 2 : Long exposure images of a levitating particle that follows a circular, trefoil, and Ultrahaptics logo trajectory.