The influence of the textile substrate on the performance of a textile-based strain sensor has not been well understood or characterized in many wearable sensor evaluations. The underlying textile has its own anisotropic mechanical behaviors due to its woven or knit fabrication process, and introduces non-trivial structural influences on integrated wearable strain sensors. This study considers stitched strain sensors of two stitch geometries, fabricated on two different knit fabrics, with the sensor stitched in different orientations with respect to the knit structure. The resulting mechanical and electrical performance is characterized under cyclic extension, as the angle of extension (relative to the fabric) is also incrementally changed. The results illustrate a shift from linear to non-linear mechanical behavior as fabric stiffness increases, and variations in behavior between stitch geometries. Results show that force direction and sensor placement both introduce variability in calculated elastic modulus, which affect sensor modeling (e.g. predicting applied force from sensor response). A novel stitch geometry (the chainstitch sensor) is characterized as having a higher gauge force and lower transverse sensitivity factor than the coverstitch sensor. This work offers insight into the textile-sensor interface and design implications for development of textile-based sensors.

Sensing edema or swelling in the body is a parameter of interest for many clinical and cosmetic applications of wearable technology. Edema creates heightened sensitivity to pressure points, making soft textile-based sensors particularly attractive. However, swelling induces slow, gradual changes in body circumferences, which can be difficult to sense accurately, especially with soft e-textile sensors. Anthropometric variability, sensor placement, and body movements further confound accuracy. Here, we explore the feasibility of accurately sensing ankle swelling through a comparative assessment of a set of sensors representing 3 soft sensing mechanisms in a linear-strain bench test under three frequency conditions. These sensors are then applied in a simulated swelling experiment to assess their performance relative to circumferential changes similar to those experienced in swelling. We find that two sensors (stitched and capacitive) demonstrate reliable performance that approximates or exceeds expert human measurement for swelling. Resistive polymer cord and capacitive sensors exhibited accurate response under medium- and high-frequency extensions.

This work translates an inspiration derived from the Disney classic `Sleeping Beauty' to realize a smart child's costume with color-changing capabilities. The dress uses addressable multi-color NeoPixel LEDs to change its surface color based on input from two wand controllers, consistent with the animated sequence in which Princess Aurora's fairy godmothers argue over the best color for her gown. The garment's construction emphasizes diffusion of emitted light to achieve a more uniform color distribution, and explores benefits and drawbacks of two manufacturing methods for embedding LED pixels: a manual method based on hand-soldered wire connections consistent with typical electronic craft, and a more scalable surface-mount manufacturing method based on stitched traces and reflow soldering.

The mechanism of astronaut injuries inside rigid spacesuits is not well understood, due to difficulty visualizing intra-spacesuit body motions. An alternative method is to record muscle activation signals with electromyography (EMG); however, the conventional EMG procedure requires bulky, extensive electrode/wire setup and is susceptible to signal noise. To address these challenges for aerospace applications of EMG, we designed a garment-based system to collect EMG data from upper body muscle activities inside spacesuits. Constructed with form-fitting textiles and careful management of on-garment tensions, our garment provides a viable non-invasive EMG study solution that maximizes applicability and subject mobility while resisting motion artifacts. The functionality and usability of our design was also validated with a human subject test, which showed standard-quality signal, easy don/doff process, minimal electrode/wire setup, and simple wire bulk management, as opposed to the conventional methods.

E-textiles that enable distribution of electronic components have advantages for wearable technology, in that functionality, power, and networking can be spread over a much larger area while preserving hand-feel and wearability. However, textile-embedded circuitry often must be machine-washable to conform to user expectations for care and maintenance, particularly for garments. In this study, we evaluate the robustness to home laundering of a previously-developed cut-and-sew technique for assembling e-textile circuits. Alternative surface insulation materials, textile substrate properties, and soldered component joints are evaluated. After around 1000 minutes (16.67 hours) of rigorous washing and drying, we measured a best-case 0% failure rate for component solder joints, and a best-case 0.38 ohm/m maximum increase in trace resistance. Liquid silicone seam sealer was effective in protecting 100% of solder joints. Two tape-type alternative surface insulation materials were effective in protecting bare traces and component attachment points respectively. Overall, results demonstrate the feasibility of producing insulated, washable cut-and-sew circuits for smart garment manufacturing.

Stitched e-textile circuits facilitate wearable, flexible, comfortable wearable technology. However, while stitched methods of e-textile circuits are common, multi-layer circuit creation remains a challenge. Here, we present methods of stitched multi-layer circuit creation using accessible tools and techniques.

The home wardrobe is a complex and variable system, interacted with daily by its user/manager in a time- and resource-constrained decision-making process. Ubiquitous computing technology offers advantages in augmenting the decision-making process, and the potential to simultaneously encourage sustainable behaviors. In this study we present an empirical analysis of the contents of 11 home wardrobes and 3-6 months of daily dressing decisions for 5 users. We find that an average of only 7% of our female participants' wardrobes and 47% of our male participants' wardrobes are in regular use. In addition, we present an analysis of wardrobe contents, outfit composition, and garment utility in the wardrobe.

One of the chief challenges of wearable sensing is adapting electronic components and sensors to the wearable environment. Electronic components are often rigid, bulky, and impermeable: factors that usually detract from wearing comfort. Here, we present a novel stretch sensor fabricated using the top thread of a standard industrial coverstitch machine. The machine is common in apparel production and offers the ability to easily fabricate custom-placed stretch sensors on textile and apparel products. The sensing properties of the stitch are enabled by a conductive thread which increases its electric resistance as the fabric is stretched, due to the geometry of the stitches. Our empirical analysis shows a sensor response in the order of 10 ohms, with almost linear behavior prior to saturation (when the stitch is fully stretched) for low-frequency extensions of 119% of initial sample length. An equivalent electrical model is presented for theoretical modeling of the sensor behavior.

Wearable technology presents a wealth of new HCI issues. In particular, this paper addresses the impact of the physical interaction between the user's body and the device's physical form on the user's mental representation of self and cognitive abilities, a blend of HCI and ergonomics that is unique to wearable computing. We explore the human sensory mechanisms that facilitate perception of worn objects and the elements of sensation that influence the comfort of worn objects, and discuss the psychological elements that may cause worn objects to be forgotten or detected, wearable or not. We discuss the implications of un-wearability on attention and cognitive capability.