“Haptic, as an adjective, means relating to the tactile sense, the sense of touch, from the Greek, haptesthai, to touch. Webopedia  defines haptics as the “science of applying tactile sensation to human interaction with computers.” A haptic device is one that involves physical contact between the computer and the user. This can be done through an input/output device that senses the body’s movements, such as a joystick or data glove. By using haptic devices, the user can not only feed information to the computer but can receive information from the computer in the form of a felt sensation on some part of the body. This is referred to as a haptic interface. Force feedback is the area of haptics that deals with devices that interact with the muscles and tendons that give the human a sensation of a force being applied—hardware and software that simulates humans’ sense of touch and feel through tactile vibrations or force feedback. These devices mainly consist of robotic manipulators that push back against a user with the forces that correspond to the environment that the virtual effector is in. Tactile feedback makes use of devices that interact with the nerve endings in the skin to indicate heat, pressure, and texture. These devices typically have been used to indicate whether or not the user is in contact with a virtual object. Other tactile feedback devices have been used to simulate the texture of a virtual object. In applied arts and design, a research fellow states, “for applied artists and designers, spatial thinking and the sense of touch is integral to the process of creativity.” – Pat Martinsen
“Tactile sensing is created by skin excitation that is usually produced by devices also called “tactile displays”, [Howe, 1999]. These skin excitations generate the sensation of contact. Tactile feedback is easier to produce than force feedback with present actuator technology, and the interface tends to be light and portable [Burdea, 1996]. Force sensitive resistors, miniature pressure transducers, ultrasonic force sensors, piezolectric sensors, vibrotactile arrays, thermal displays and electro-rheological devices are some of the innovative technologies that have been used to generate the feeling of touch.” (src: http://220.127.116.11/search?q=cache:zdL57CzYGJ8J:cronos.rutgers.edu/~mavro/papers/Ch10-2-haptic.PDF+%22thermal+displays%22&hl=en&ie=UTF-8)
“Tactile display devices stimulate the skin to generate these sensations of contact. The term “tactile display” is sometimes used to describe any apparatus that provides haptic feedback, but it's useful to distinguish between systems for vector force feedback and devices that convey distributed sensations. The skin responds to several distributed physical quantities; the most important are perhaps high-frequency vibrations, small-scale shape or pressure distribution, and thermal properties.
Many other tactile display modalities have been demonstrated, including electrorheological devices for conveying compliance, electrocutaneous stimulators, ultrasonic friction displays, and rotating disks for creating slip sensations. ”
Robert Howe, Harvard University (from: http://haptic.mech.nwu.edu/TactileDisplay.html)
in parts see: Actuator Technology
Karon E. Maclean
Grigori E Evreinov (multi-modal interaction research group at the university of Tampere)