Shibata Technotex Co Ltd (Ichinomiya City, Aichi Prefecture) exhibited a flat speaker woven with copper, stainless steel, etc at Semicon Japan 2017, which took place from Dec 13 to 15, 2017, at Tokyo Big Sight.
Shibata Technotex is a fabric manufacturer founded in 1947 and developing smart textiles that interweave "conductive thread," which is made by winding copper, stainless steel, etc around polyester, as one of its new businesses. Conductive thread is entirely covered with copper, stainless steel, etc, and it can be soldered.
It can be woven into a cloth and used as wiring, and it can be used as a connection port for the "LilyPad" device that can be stitched into clothes. The stainless conductive thread is also washable.
The planar capacitor speaker that is made of cloth and was exhibited at Shibata Technotex's booth has a conductive film that functions as a vibration film between two pieces of conductive fabric. Sound source signals whose plus and minus are inverted flow in the conductive fabric. When the vibration film is placed on the ground, the film is attracted to the conductive fabric on the "plus" side. When this is repeated, sound is produced.
In a demonstration of connecting a smartphone playing music and an amplifier, while the appearance and touch feeling (softness) of speaker were equivalent to those of normal clothes, the speaker had a high directivity, and the music can be heard even at the noisy exhibition site.