“…In recent years, different research groups have developed laboratory prototypes of haptic display devices based on different principles. Haptic display devices previously developed explore servomotors (Wagner et al, 2002), electromagnetic coils (Benali-Khoudja et al, 2004), piezoelectric ceramics (Pasquero, Hayward, 2003) (Chanter, Summers, 2001) (Maucher et al, 2001), pneumatics (Moy et al, 2000), shape memory alloys (SMA) (Kontarinis et al, 1995) (Taylor, Creed, 1995) (Taylor et al,1997) (Taylor, Moser, 1998), Electro-magnetic (Fukuda et al,1997) (Shinohara et al, 1998), polymer gels (Voyles et al, 1996) and fluids as actuation technologies (Taylor et al, 1996). A softness haptic display is important to distinguish between the different objects.…”