Measurement of Parachute Canopy Textile Deformation Using Mechanically Invisible Stretchable Lightguides

Abstract

Conventional strain gauges are not designed for accurate measurement over the large range of deformations possible in compliant textiles. The thin, lightweight, and flexible nature of textiles also makes it challenging to attach strain gauges in a way that does not affect the mechanical properties. In this manuscript, soft, highly extensible fibers that propagate light (i.e., stretchable lightguides) are stitched as a strain gauge to map the deformation of a nylon parachute textile under tension. When under load, these fiber optic strain gauges propagate less light, and this strain‐induced light modulation is used to accurately (absolute error≈2.93%; Std. Dev.: 3.02%) measure strain in the <30% range before these textiles fail. This system has directionality; strain in parallel to the sensor results in little light attenuation while perpendicular loading shows high sensitivity (Gauge factor⊥≈24.8 and Gauge factor||≈0.05 at the first 1% strain). Structural and optical simulations are coupled to demonstrate that load transfer on the fiber optic by the stitchwork is the dominating cause of signal modulation. To further validate the hypotheses, digital image correlation was used under dynamic loading conditions to show that these sensors do not significantly affect the mechanical properties.

Packaged Elastomeric Optical Fiber Sensors for Healthcare Monitoring and Human‐Machine Interaction

“…Moreover, the flexible but non-stretchable silica fibers used for fabricating FBG may run the risk of influencing the local mechanical properties of the substrate they are embedded in or may break during large strains. [27] Different from the non-stretchable silica or polymer materials such as polymethyl-methacrylate (PMMA) and polystyrene (PS), elastomers offer excellent stretchability, high transparency, high mechanic strength, and softness, making elastomeric polymer optical fiber (EPOF) a promising candidate to fabricate wearable sensors with excellent performances. Typically, to fabricate an EPOF with a core of high refractive index and a cladding of low refractive index, one can employ coaxial 3D printing, [28] clad coating, [29] coextrusion, [30] thermal drawing [31] or molding [32] methods.…”

“…Moreover, the flexible but non‐stretchable silica fibers used for fabricating FBG may run the risk of influencing the local mechanical properties of the substrate they are embedded in or may break during large strains. [ 27 ]…”

Autonomous self-healing optical sensors for damage intelligent soft-bodied systems

“…Combined with advances in artificial intelligence, SHeaLDS presents a route toward more enduring and adaptive robots. Beyond robotics, we envision SHeaLDS to find utility in the broader area where damage intelligence is essential in damage-prone environments, such spacesuits and supersonic parachute monitoring in space ( 44 ), as well as applications where device longevity is preferred, such as wearables for human machine interaction and digital health.…”

Machine Embroidery Enclosure for Stretchable Fiber Optic Respiration Sensor

“…[33] On the other hand, measuring the light intensity or color only requires a small detector, which provides a user with better wearability, as well as high sensitivity. [22,[44][45][46] Lastly, elongation-or compression-based strain sensing requires either a pre-strain to avoid non-linear signal changes or a high stress than bending, which will introduce a stronger tension around the body. [35,45,47] Controlling the fiber movement is important to ensure consistency in macro-bending methods, but most applications so far have only secured the fiber permanently using glue or stitches at a few fixed points, which has allowed the rest of the fiber to arbitrarily bend without any control or guidance.…”

“…[22,[44][45][46] Lastly, elongation-or compression-based strain sensing requires either a pre-strain to avoid non-linear signal changes or a high stress than bending, which will introduce a stronger tension around the body. [35,45,47] Controlling the fiber movement is important to ensure consistency in macro-bending methods, but most applications so far have only secured the fiber permanently using glue or stitches at a few fixed points, which has allowed the rest of the fiber to arbitrarily bend without any control or guidance. [30,44,46,48] This study reports on an unobtrusive and stretchable respiratory monitoring system consisting of an elastomeric optical fiber, called Optical Lace (OL) and an embroidered enclosure.…”