Perfusable Knits—Knitted Silicone Tube for Wearable Device

<b><i>Background. </i></b>Wearable devices with embedded fluidic channels have demonstrated reconfigurable applications as fluid-based sensors and actuators (e.g., conductive ink, liquid metal and compressed air). Methods for fabricating flexible constructs with fluidic channels are essential for the development of wearable devices with advanced functions. Currently available fabrication methods are primarily based on soft lithography and three-dimensional (3D) printing, however, which are yet suboptimal in terms of fabricating embedded fluidic channels in large surface areas with complex 3D structures.<br/><br/><b><i>Contribution. </i></b>We present an alternative route to fabricate channel-embedded, flexible constructs by knitting silicone tubes and structural yarns, which we termed perfusable knit (PK). Silicone tubes serve as both the structural components (i.e., the part constituting the textile and garments) and the functional components (i.e., the part where functional fluids are infused or perfused).<br/><br/><b><i>Techincal achievement. </i></b>PK was fabricated with a manual knitting machine using commercially available silicone tubes with 2-mm outer diameter (OD) and 1-mm inner diameter (ID). Fabrication of two-dimensional (2D) textile and three-dimensional (3D) wearable devices was readily achieved by this approach. We identified knitting gauges and patterns of knitting (e.g., jersey, rib and garter) suitable for the fabrication of 3D knitted structures. Inlay knitting with an automated knitting machine was also demonstrated to integrate silicone tubes with the textile, which served as another platform to handle liquid embedded in the textile. Tensile tests confirmed that the elongation of the textile knitted with silicone tubes was anisotropic in terms of stretchability. The textile made of the silicone tube filled with conductive ink exhibited deformation-specific electrical responses that can be used for motion sensing. Crucially, the mechanical anisotropy affected the electrical responses exhibited by embedded conductive inks. As a demonstration, a wearable force sensor in the form of a mitten consisting of silicone tube, acrylic yarn, and conductive fluids were developed for motion sensing of the finger using electrical resistance.<br/><br/><b><i>Significance.</i></b> Overall, we developed a unique fabrication method for flexible and wearable devices by directly knitting perfusable silicone tubes. We envisage that PK will provide alternative routes for the design and fabrication of 3D wearable devices containing functional fluids, allowing for the sensing of electrical and chemical signals using sensors integrated into garments.