Browsing by Author "Henrich, Mauricio Carlos"
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Item Encoding contact size using static and dynamic electrotactile finger stimulation: natural decoding vs. trained cues(2024) Henrich, Mauricio Carlos; Garenfeld, Martin A.; Malesevic, Jovana; Strbac, Matija; Dosen, Strahinja; SGElectrotactile stimulation through matrix electrodes is a promising technology to restore high-resolution tactile feedback in extended reality applications. One of the fundamental tactile effects that should be simulated is the change in the size of the contact between the finger and a virtual object. The present study investigated how participants perceive the increase of stimulation area when stimulating the index finger using static or dynamic (moving) stimuli produced by activating 1 to 6 electrode pads. To assess the ability to interpret the stimulation from the natural cues (natural decoding), without any prior training, the participants were instructed to draw the size of the stimulated area and identify the size difference when comparing two consecutive stimulations. To investigate if other “non-natural” cues can improve the size estimation, the participants were asked to enumerate the number of active pads following a training protocol. The results demonstrated that participants could perceive the change in size without prior training (e.g., the estimated area correlated with the stimulated area, p < 0.001; ≥ two-pad difference recognized with > 80% success rate). However, natural decoding was also challenging, as the response area changed gradually and sometimes in complex patterns when increasing the number of active pads (e.g., four extra pads needed for the statistically significant difference). Nevertheless, by training the participants to utilize additional cues the limitations of natural perception could be compensated. After the training, the mismatch in the activated and estimated number of pads was less than one pad regardless of the stimulus size. Finally, introducing the movement of the stimulus substantially improved discrimination (e.g., 100% median success rate to recognize ≥ one-pad difference). The present study, therefore, provides insights into stimulation size perception, and practical guidelines on how to modulate pad activation to change the perceived size in static and dynamic scenarios.Item Novel Electrode Designs for Electrotactile Stimulation of the Finger: A Comparative Assessment(2023-10-01) Garenfeld, Martin A.; Henrich, Mauricio Carlos; Isakovic, Milica; Malesevic, Jovana; Strbac, Matija; Dosen, Strahinja; SGElectrotactile stimulation can be an attractive technology to restore tactile feedback in different application scenarios (e.g., virtual and augmented reality, tele-manipulation). This technology allows designing compact solutions with no mechanical elements that can integrate a high-density matrix of stimulation points. The present study introduced four novel multi-pad finger-electrode designs with different arrangements (two matrix and two circular) and shapes of active pads (producing sensation) and reference pads (ideally, no sensation produced below the pad). The electrodes were used to investigate the subjects' ability to spatially discriminate active pads within phalanges individually (6-9 pads) as well as across the full finger (18-19 pads). The tests were conducted in 12 subjects and the results showed that all designs led to high success rates when applied to the fingertip (70-81%). When tested on the full finger, the matrix and circular designs were characterized with similar performance (54-57%), and when the phalanges were analyzed individually, the spatial discrimination was best at the fingertip. Additionally, new approaches for faster amplitude calibration were proposed and tested, demonstrating that calibration duration can be reduced by approximately 40% compared to the standard approach of calibrating single pads individually. Finally, discrimination tests of dynamic tactile patterns were conducted using circular and matrix designs on the fingertip and full finger, respectively. The tests showed that the different patterns generated by the two arrangements could be clearly discriminated, especially in the case of full-finger matrix-style patterns. The present study, therefore, provides several important insights that are relevant when delivering tactile feedback to the finger using an electrotactile interface.