Graphic by Megan Eloise/The GazelleImagine that you are feeling a random tickle or a sensation of touch somewhere on your body without seeing or hearing anything come in contact with your skin. Thanks to technological advances in haptics technologies, a research field that studies the incorporation of touch in human-computer interaction, there is little need for imagination any longer. This is becoming a reality.

Touch plays a prominent role in interpersonal communication. Haptics, a term derived from the Greek verb “haptesthai” meaning “to touch”, refers to the science of sensing and manipulating through touch. Early research on haptic stimulation has focused on applications aiding blind or visually impaired people, but later developments span a wide spectrum of applications including entertainment and gaming, mobile and touchscreen interaction, emotional and interpersonal communication, health care such as physical rehabilitation and Tele-surgery, Tele-robotics and Tele-operation, education, training and e-commerce.

Traditionally, a haptic device is a mechanical apparatus that is used to exchange forces between a computer and a user. These devices are typically classified as either force feedback or tactile. Kinesthetic devices display forces or motions through robotic interfaces and are typically used to communicate relatively large forces to emulate weight or collision forces.

Tactile haptic devices stimulate the skin in order to simulate texture sensation, typically achieved through the generation of vibrations. Crucial limitations in existing haptic devices include their bulkiness to wear and the requirement to make physical contact between the device and the user, both of which result in diluting the user experience due to the discomfort of wearing a haptic device.

Furthermore, contact-based haptic devices may be problematic in several application scenarios such as hospitals or public toilets for hygienic reasons or payment smart cards for security reasons. For instance, capable hackers can dust down the secure touchscreen of some passcode-protected base and glean, from the ultraviolet-visible fingerprints, the exact numbers necessary for entry. Having a system where you do not need to touch the screen to interact with it provides a safer way of communication.

The Applied Interactive Multimedia laboratory at NYU Abu Dhabi is developing a technology, named Haptogram, which enables contactless tactile stimulation using focused ultrasound waves. The concept is based on that of a hologram: using a two-dimensional array of transducers that produce synchronized ultrasonic waves to generate a point of compressed air in 3-D space. The pressure is intense enough that humans can feel it with their bare skin. By controlling the transducers array, one can generate focal points at an arbitrary location within a 3-D space facing the array. Moreover, the focal point can be programmatically controlled to move from one position to another to create an apparent tactile motion. Most interestingly, by animating the focal points at a very high speed, 3-D tactile objects can be generated in midair. A snapshot of a 4-tiles implementation of the Haptogram system is shown in Figure 1.

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The Haptogram system comprises a software component and a hardware component. The software component enables users to author and/or select a tactile object, convert the object into a point-cloud and generate a sequence of focal points to drive the hardware.

The hardware component is made up of a grid of ultrasound tiles, consisting of 2-D arrays of ultrasound transducers. A quantitative analysis is conducted to measure the Haptogram’s ability to display various tactile shapes, including a single point, a 2-D straight line and a circle and a 3-D hemisphere. Results show that all displayed tactile objects are perceivable by the human skin.

A usability study was also conducted to evaluate the ability of humans to recognize 2-D shapes where four 2-D shapes were considered: circle, triangle, line and plus. Results show that the recognition rate was well above the chance level, while the recognition time has an average of 13.87 seconds and a standard deviation of 3.92 seconds. These results are promising and confirm that the Haptogram technology is an effective means for communicating tactile sensation to the users without any physical contact. A snapshot of a user performing the experiment is shown in Figure 2.

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We believe that the Haptogram technology has great potential in future applications, especially those related to virtual reality, gaming and entertainment, education and training and human-human and human-robot interactions.

One promising application in virtual reality is to create touchable holograms. Users will be free to move their hands around the hologram display, a hand motion tracker captures in real-time the position of the user’s hands, and tactile stimulation is generated whenever a collision is detected between the displayed avatar and the user’s hands so users feel the touch of the virtual avatar.

This would enhance the quality of immersion through multimodal interaction and the overall user experience by enabling users to explore the physical properties in addition to the graphic properties of the displayed hologram. In the near future, we firmly believe that the emerging reality of contactless touch will become commonplace in far more applications and areas.

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