Ms. Sukhneet K. Dhillon Profile

Sukhneet K. Dhillon

at Univ of British Columbia

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Publications (3)

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Proceedings Article | 28 April 2023 Poster

The use of nylon actuators within an active textile for applications in compression therapies

Sukhneet Dhillon, Ying Li, Adriana Cowan, Magan Chang, Tony Huang, Konstantin Borissov, John Madden

Proceedings Volume PC12482, PC124820P (2023) https://doi.org/10.1117/12.2667947

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Nylon actuators yield a large reversible strain (5-20%+), are compact (300-µm) and provide a low-cost option for biomedical applications. We propose to develop an active textile composed of cotton, silver-coated nylon, and nylon actuators. We will assess the feasibility of nylon actuators to generate effective cycle rates and compression pressures similar to those of clinically effective pneumatic compression pumps. Our aim is to establish correlations between three nylon actuator configurations (parallel, parallel at 30°, and crisscrossed at 30°), thermal distribution, and compression pressure, as well as between power input and nylon actuator cycle rate. A microcontroller unit (MCU) and a pressure sensor will be developed for the nylon actuators to ensure that the actuators are under constant strain, while monitoring pressure, current, voltage and temperature. The development of an actively contracting textile could have significant benefits for portable compression therapies.

Proceedings Article | 20 April 2022 Presentation + Paper

Active cooling techniques for coiled nylon actuators

Sukhneet Dhillon, Soheil Kianzad, Milind Pandit, Meisam Farajollahi, John Madden

Proceedings Volume 12042, 1204218 (2022) https://doi.org/10.1117/12.2615205

KEYWORDS: Actuators, Coating, Convection, Silver, Shape memory alloys, Robotics, Thin film coatings, Resistance, Thermal modeling, Water

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Low-cost, highly versatile thermally driven coiled nylon actuators have demonstrated great tensile stress (>10 MPa) and large stroke (>5%). The work density of this material is 100 times greater than mammalian muscle, which makes coiled nylon actuators good candidates for applications in soft robotics. Similar to other thermally driven actuators, heat transfer rate limits their frequency response and benefits from extensive cooling. The cooling time for these actuators is dependent on heat conduction and convection. For instance, an 860 µm multi-stranded coiled nylon actuator is limited to 0.2 Hz frequency of actuation, above which tensile stroke drops due to heat accumulation. We analyzed the thermal behavior of silver-coated nylon actuators and investigated the actuation under air flow, in hydrogel, and in water, to improve the frequency response. An improved frequency response was observed under air flow (compressed air) in relation to still air. The measured heat transfer coefficient under air flow reaches 137 W/m² /K enabling 5% strain at 0.8 Hz. The fastest frequency responses were observed in water and within hydrogel, where the nylon actuators demonstrated ~10% strain at 1 Hz (add water and hydrogel heat transfer coefficient). The application of a hydrogel coated actuator is demonstrated through an actuated 3D printed finger, which makes use of antagonistic coiled nylon actuators.

Proceedings Article | 20 April 2022 Poster + Paper

Combined hydrogel and elastomer coatings for cooling supercoiled nylon actuators

Sukhneet Dhillon, Ali Redha Muljiani, Henry Tran, Soheil Kianzad, John D. Madden

Proceedings Volume 12042, 1204219 (2022) https://doi.org/10.1117/12.2638057

KEYWORDS: Actuators, Fiber coatings, Artificial muscles, Ultraviolet radiation, Polymerization, 3D modeling

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Silver-coated nylon actuators - a form of artificial muscle - are potential candidates in biomedical applications, , as they yield a large strain (5-20%+), high force (>20 MN/m² ), are compact and low-cost. But the on skin or internal application of these thermal actuators is limited by the heat released and the high activation temperatures (typically >80°C), which could cause tissue damage. We present a hybrid coating that reduces the temperature at the interface of the nylon actuator and surrounding tissue/skin, while maintaining the inner nylon actuator activation temperature. By taking advantage of the high heat capacity of water-swollen polyacrylamide (PAAm) hydrogel and the low thermal conductivity of silicone elastomer, we develop a hybrid coating for nylon actuators that provides effective heat dissipation and encapsulation without impacting strain. Hydrogel is used to absorb and dissipate heat. Using it alone dissipates heat quickly, and in turn, excess power is needed to achieve full strain. Therefore, silicone is used as a thin, inner insulating layer to retain the heat, so full strain can be achieved without excess power. We examined the strain and temperature of uncoated nylon fibres (control), single-layered silicone-coated nylon fibres, single-layered hydrogel nylon fibres and hybrid-coated (inner layer of silicone, outer layer of hydrogel) nylon fibres. At a constant current of 0.55 A, the mean strains of hybrid coated nylon fibres (6.0 %), and silicone coated nylon fibres (5.5%) were comparable to uncoated nylon fibres (5.3%). The mean strain for the hydrogel-coated nylon fibres was considerably lower (1.4%). The hybrid coating effectively maintains the fibre temperature (80-87°C) while cooling the outer surface (hydrogel) of the hybrid-coated nylon fibre (30-35°C). This provides a possible solution for use of these actuators in temperature sensitive applications.

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