Rehabilitation Engineering and Electromechanical Design Lab
This research focuses on thermal haptics, how humans perceive temperature, and how the brain and temperature interact with each other. In the field of haptics, researchers have mostly focused on fast-response modality cues such as vibrations and forces due to their promising potentials in conveying information to the user. On the contrary, thermal haptics has not been investigated as much as needed due to slow-response characteristics and difficulty in actuating thermal stimulus. Thermal cues have great potential for gaming, psychological, and medical applications as well as applications in VR. In a series of studies, we investigate the effect of temperature on the body, brain, and emotions as well as biological theories related to temperature perception.
In previous studies on asymmetric thermal stimulation, it has been demonstrated that the application of rapidly cooling and slowly heating temperature grids on the skin elicits constant cooling perception when the overall temperature of the skin is not changed. Manasrah et al. (2017) discovered this effect for the first time. The effect makes use of the fact that hot and cold receptors have different nonlinear thresholds. In an extension of the mentioned study, a modified asymmetric thermal pattern was proposed to intensify the cooling/heating perception. The improvement of the perception was sought by overlapping rapidly changing temperature patterns. Three sets of experiments with different neutral temperature criteria were conducted. These patterns lead to a counter-intuitive perception, which was the opposite of what was observed in previous studies.
Verifying the thermal response of skin was not possible during the psychophysical experiment of asymmetric thermal stimulation. Therefore, a physical representation of the arm was developed enabling us to measure the temperatures and heat transfer rate at/under the surface of the skin. Thermal interactions were verified by simulating the thermal patterns through computational analysis in ANSYS. Results from the physical and computational simulations demonstrated that asymmetric thermal patterns exist at different depths of the skin under the actuators. This confirmed our hypothesis that thermal patterns are sensed by thermal receptors which are at a deeper level of the skin.
Perceptual anomalies are utilized to help scientists investigate the underlying processes of biological mechanisms, forming perceptions. The thermal grill illusion (TGI), sometimes called synthetic heat, is described as a burning pain sensation caused by placing very hot and cold objects in the neighboring parts of the skin. There are conflicting theories, each explaining the TGI to a limited extent. Identifying the most accurate explanation can elucidate the thermal perception process. A series of TGI-inducing temperature profiles are developed to be tested on human arms. The experiments will be performed using a novel experimental setup, conducting psychophysical experiments.
This work was supported by the National Science Foundation under Grant IIS-1526475.
Last modified on Apr 30, 2020.