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Gao, Jian

University of British Columbia

Soft flexible force sensors are highly desired in the world of wearables for health monitoring applications and novel human-computer interfaces. To this end, a variety of flexible conductive materials have been investigated as electrodes under various sensing schemes. However, many of the proposed sensors, characterized in laboratory environments, have not been successfully deployed as standalone wearable devices due to high power consumption, bulky electronics, and noise in sensor signals introduced by human bodies. Meanwhile, the complexity and expensive materials in several sensor designs added to the difficulty in mass production. In this thesis, we propose a soft flexible capacitive force sensing system that is low in power (20 mW), low in cost (<10 USD per sensor), fast in scanning (max 10,000 points per second), and Bluetooth-enabled (max 2 Mbps bandwidth). By measuring mutual capacitances between electrodes with specific spatial arrangement, our sensing system captures multiple modalities of information such as normal force, shear, and proximity. Composed with sensing points in an array, our sensors adapt well in the wearable context consisting of custom Flexible Printed Circuit Boards, stretchable conductive fabric, and silicone rubber. As the first example, for foot plantar pressure analysis, an insole sensor is demonstrated to capture normal force at 80 locations with 2.6 kPa-1 sensitivity (0-28 kPa) and shear force at 16 locations with 2.8 kPa-1 sensitivity (0-14 kPa). The second example is a watchband sensor designed to gather touch input to a smartwatch. Gestures of press, slide, and pinch can be picked up by the sensor and interpreted as commands. For both examples, normal force, shear, and proximity are visualized in a custom iOS/iPadOS/watchOS app, showing great user friendliness of the proposed sensing system towards many wearable applications.

Text

2024-09-30

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/85767

Electrical and Computer Engineering

University of British Columbia

UBCV

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