A pressure-sensitive palatograph for speech analysis

Electropalatography (EPG) is a clinical technique used to monitor contacts between the tongue and the hard palate, thus promoting correct articulation mechanisms. Currently, employed commercial tools have a good resolution but they do not provide contact pressure information. In this work, textile-based sensing technologies were employed to realize an innovative EPG tool able to both maintain the proper spatial resolution and perform quantitative pressure detection. The single sensing unit was developed using a thin polymeric sheet with a central hole, sandwiched between two piezoresistive fabric layers. Under load application, the two textile layers come into contact and the resistance of the sensor reduces significantly, measuring pressure in the range from 0 to 30 kPa. The complete prototype is composed of 62 sensing units disposed in a matrix structure: the dielectric layer contains all the sites arranged in rows and columns, according to the topography of the traditional tools, and this layer presents on both sides strips of piezoresistive textile. The entire system was covered with a thin latex membrane and fixed on a hard custom acrylic palate for the experimental characterization. The system was tested on a healthy subject, confirming the adequacy and effectiveness of the soft sensing technologies for the measuring of the tongue pressure during speech.