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Touchscreen-friendly fingertip system for tactile feedback in prosthetic hands

University of British Columbia

Today’s prostheses provide numerous intuitive features including several gripping patterns and movements guided by the user’s intentions. Nevertheless, users remain quite dependent on visual and auditory cues when trying to adjust grip forces, and are still unable to use their touchscreens with prosthetic fingertips. To approach this problem, researchers have proven that sensory feedback can help amputees to be faster and more accurate when accomplishing a task. However, there is still a need for a low-cost and adaptable sensory feedback add-on, requiring minimal modifications to the hand. This thesis presents the development of a low-cost sensory feedback system, including a stimulation device and a force sensing fingertip that comprises a capacitive sensor. The novelty of this research is the ability of the fingertip to activate touchscreens, and the full fingertip integration to the prosthetic hand, under the prosthetic glove – easy for the user to maintain. The glove integrated sensor capacitively detects forces over an area of 0.64 cm2. This detection is linear up to 1.6 N, with a resolution of 0.01 N. The second part of this thesis presents the implementation of shear detection, in addition to touch and pressure, using a modified sensor on a flexible printed circuit board. Able to detect touch, pressure, and shear simultaneously, the sensitive fingertip can send sensory feedback to the user. The last part of this thesis presents the implementation of two sensory feedback: one using an armband including a servo motor pushing on the user’s stump (mechanotactile feedback), and one using vibration motors hidden in the socket (vibrotactile feedback) – two feedbacks that are preferred based on a survey that we conducted. It was found that vibrotactile feedback would be more efficient due to its complete integration to the hand and its ability to send shear feedback. The next steps are the implementation of Bluetooth connections for wireless stimulation and the development of a user iv interface for real-time calibration. An ethics approval to test the device on patients was granted and will be put into practice to understand the benefits of the device and gather users’ opinions.

Text

2021-08-31

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/75772

Biomedical Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/