TOUCH-SENSITIVE CLADDING PANELS USING SURFACE ACOUSTIC WAVES
In modern electronics a wide variety of touch sensitive controls are implemented, ranging
from push-buttons to capacitive touch sensors. Push-buttons are typically implemented by
creating holes in a surface panel, in which the push-buttons are placed. This can make the device
sensitive to humidity and dirt in the environment. On the other hand, capacitive touch
sensors can avoid this problem. However, only non-conductive surfaces can be functionalized
using this method and detectability is reduced when gloves are worn.
The inventors suggest a method and device based on Lamb-waves, the underlying effect beeing
radiation loss. This arises when the surface, which is conducting the wave, is brought into
contact with a soft or liquid medium whose velocity of sound is smaller than that of the conducting
material. The invented methode has the advantage that the front-side of the cladding
panel can remain unchanged since the sensors are attached to the back-side¹. Furthermore,
the functional concept can be applied to almost all sheeting materials (metal, ceramic, wood,
plastic). Finally, the touch position can be detected by including partially reflecting elements,
such as grooves and edges². The back reflected signals from reflectors in front of the touch
position are unaltered, whereas the back reflections from reflectors behind the touch position
Typical use cases are manual controls in automotive industry or other machinery, where the invented method can be used to functionalize panels in the interior. Further applications include home appliances or even smart home systems, where functionalized bathroom tiles can detect falls and serve as an early warning system for flooding.
Prototype has been successfully tested.
Figure: (Top) Showing the simplest implementation of the suggested device and method. A finger in contact with the panel attenuates the propagating wave. (Bottom) Illustration of two use cases discussed above³.
1) C. Yu et al., Proc. Sensor 2013, p. 766–771 (2013), doi: 10.5162/IMCS2012/P4.4
3) L. Meisenbach et al., Proc. AAL 2011, 87, (2011)