KnitDermis — Hybrid Body Lab

Knitdermis: Knitted tactile on-body interfaces

A knitted smart tattoo that pinches or strokes your skin? KnitDermis on-body interfaces deliver expressive tactile feedback on the wearer’s body. Fabricated through machine knitting, they embed shape-memory alloy micro-springs in knitted channels, which deliver tactile sensations on the skin when activated.

We present KnitDermis, on-body interfaces that deliver expressive non-vibrating mechanotactile feedback on the wearer’s body. Fabricated through machine knitting, they embed shape-memory alloy micro-springs in knitted channels, which deliver tactile sensations on the skin when activated. KnitDermis interfaces take advantage of machine knitting’s shaping properties which allow it to generate slim, stretchable, and versatile forms that can conform to underexplored body locations, such as protruded joints and convex body locations. We introduce a fabrication approach and a series of case studies to design a wide range of form factors, textures, and tactile patterns, including compression, pinching, brushing, and twisting. We conduct a user study to elicit KnitDermis’ effectiveness and wearability on diverse body locations and engage users to unpack envisioned use cases and perceptions towards the interfaces. We draw insights from our extensive research-through-design investigations on the potential of knitting as a soft approach for close-body and expressive tactile interfaces.

Publication:
KnitDermis: Fabricating Tactile On-Body Interfaces Through Machine Knitting Jin Hee (Heather) Kim, Kunpeng Huang, Simone White, Melissa Conroy, Cindy Hsin-Liu Kao ACM Designing Interactive Systems (DIS) 2021 BEST PAPER HONORABLE MENTION AWARD PDF I DOI

Project Credits: Hybrid Body Lab at Cornell University, directed by Cindy Hsin-Liu Kao
Research Team: Jin Hee (Heather) Kim (Lead Researcher), Kunpeng Huang, Simone White, Melissa Conroy, Prof. Cindy Hsin-Liu Kao

Press Inquiries: Press Image Kit: Available Upon Request (License: CC by-NC-SA 4.0) Press Contact: Prof. Dr. Cindy Hsin-Liu Kao, cindykao@cornell.edu

Acknowledgements

This project was supported in part by the Center for Craft Materials-Based Research Grant and the National Science Foundation under Grant IIS-2047249.

KnitDermis on-body interfaces deliver expressive tactile feedback on the wearer’s body. Fabricated through machine knitting, they embed shape-memory alloy micro-springs in knitted channels, which deliver tactile sensations on the skin when activated. KnitDermis interfaces take advantage of the shaping properties of machine knitting for slim, stretchable, and versatile forms that conform to underexplored body locations, such as (a) protruded joints and (b) convex (hollow) body locations, delivering sensations from (a) compression, (b) pinching, (c) brushing, to twisting. We introduce knitting as a soft approach for crafting expressive and personal tactile interfaces. Here is the KnitDermis compression interface during actuation while worn on the knuckles. (Image Credit: Hybrid Body Lab) (License: CC BY-NC-SA 4.0)

KnitDermis brushing interface during actuation. (Image Credit: Hybrid Body Lab) (License: CC BY-NC-SA 4.0)

KnitDermis pinch interface during actuation while worn on the hand. (Image Credit: Hybrid Body Lab) (License: CC BY-NC-SA 4.0)

KnitDermis twisting interface during actuation. (Image Credit: Hybrid Body Lab) (License: CC BY-NC-SA 4.0)

KnitDermis pinch interface during actuation while worn on the ankle. (Image Credit: Hybrid Body Lab) (License: CC BY-NC-SA 4.0)

KnitDermis compression interface during actuation while worn on the forearm. (Image Credit: Hybrid Body Lab) (License: CC BY-NC-SA 4.0)

The main design factors for KnitDermis interfaces consist of actuation mechanism (a), spatial manipulation of SMA (b), and body location (c). Actuation is achieved either through shifting the skin in various directions (a1-2) or morphing the interface itself radially (a3) and longitudinally (a4). More specific design of haptic feedback is enabled by shaping SMA (b). A set of crossing linear lines can yield different forces depending on the skin area in contact (b1). Open free form curves can be used to enlarge the skin area being affected (b2). Closed curves can work in concert with underlying skin geometry (b3). By altering parameters (length, curvature, or distance) of SMA placement, haptic sensation can be fine tuned. KnitDermis can be applied on a variety of unexplored body locations such as cylindrical or planar spots (c1), protruded spots (c2), and concave spots (c3). (Image Credit: Hybrid Body Lab) (License: CC BY-NC-SA 4.0)

A catalogue of knit structures adopted by KnitDermis. Tubular jacquard (a) is used to encase active and passive materials. With complete freedom in size and shape, tubular jacquard can create channels to accommodate yarn-like materials (a1), let materials cross each other (a2) or create a pocket to accommodate larger components. By manipulating stitches (b) KnitDermis’ interfaces can contour body topography (b1-2). Modifying the stitches can also perforate the substrate to connect the materials to power source or other components (b3). Volumetric shaping can be achieved through skipping a section of needles for "short rows" (c1) or combining heterogeneous structures (c2). (Image Credit: Hybrid Body Lab) (License: CC BY-NC-SA 4.0)

Summary of eight KnitDermis case studies. Depending on haptic feedback of interest, each case study variously configures design factors to conform to specific body locations. B-wrist and C-wrist adopt self-shifting mechanism whereas the remainder utilizes skin-shifting mechanism. (Image Credit: Hybrid Body Lab) (License: CC BY-NC-SA 4.0)

KnitDermis ACM DIS 2021 Conference Presentation by Ph.D. researcher Heather Kim