Stretchable Fiber Optic Pressure Sensors for Comfortable Gait Tracking
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Solution Overview
Problem
Conventional plantar pressure sensors are expensive, uncomfortable, unreliable, and restrictive, with issues such as slippery surfaces, stiffness, bulkiness, and sensitivity to environmental factors, limiting their suitability for daily use in monitoring gait and body balance.
Innovation Solution
A stretchable fiber optic pressure sensor using deformable optical fibers that change light transmission based on applied force, providing a lightweight, breathable, and flexible solution for plantar pressure tracking, capable of generating two-dimensional pressure maps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional plantar pressure sensors use thin conductive film layers and printed circuit board structures, then pressure sensing capability is achieved, but the device becomes bulky, heavy, and uncomfortable for everyday use
Solution Approach 1:
The patent replaces conventional electrical resistance-based pressure sensing with optical fiber-based sensing. Optical fibers detect pressure through light transmission changes when deformed, eliminating the need for heavy conductive films, printed circuit boards, and electronic components. This substitution achieves accurate pressure sensing while dramatically reducing weight and bulk, making the insole comfortable for everyday wear.
Solution Approach 2:
The patent uses thin, flexible optical fiber layers integrated into the insole structure. These optical fibers are embedded within the insole material, allowing the sensor to conform to the foot's shape without adding significant thickness or rigidity. The flexible optical fiber structure maintains pressure sensing capability while ensuring comfort and natural foot movement.
2Reliability
If conventional plantar pressure sensors use dielectric film with slippery surface interface, then electrical insulation is achieved, but the sensor cannot simulate actual foot-interface interaction and creates safety issues during intense movements
Solution Approach 1:
The patent replaces electrical insulation requirements with optical isolation. Since optical fibers transmit light rather than electricity, there is no need for dielectric films to prevent electrical conduction. This eliminates the slippery surface problem and allows the insole to provide accurate friction and grip during intense movements, truly simulating natural foot-interface interaction.
Solution Approach 2:
The patent changes the fundamental sensing parameter from electrical properties (resistance, capacitance) to optical properties (light transmission intensity). This parameter change eliminates the need for dielectric materials and their associated slippery surface issues, while enabling accurate detection of pressure and friction forces during dynamic activities.
3Strength
If conventional plantar pressure sensors use stiff plastic sensing pads, then structural support is achieved, but abnormal peak pressures are created at the edges
Solution Approach 1:
The patent uses flexible optical fiber layers instead of stiff plastic pads. These optical fibers are embedded within compliant insole material that can conform to the foot's contour and distribute pressure evenly. The flexible structure eliminates edge effects and abnormal peak pressures while maintaining adequate structural support through the optical fiber network.
Solution Approach 2:
The patent creates a composite structure combining optical fibers with flexible insole materials. This composite approach provides structural support through the optical fiber network while maintaining pressure distribution accuracy through the compliant matrix material, eliminating the need for stiff plastic components.
4Reliability
If conventional plantar pressure sensors use resistive pressure sensing with soft conductive material deformation, then pressure detection is achieved, but repeatability and reliability decrease
Solution Approach 1:
The patent replaces resistive pressure sensing based on conductive material deformation with optical fiber deformation sensing. Optical fibers maintain consistent light transmission characteristics during deformation and recovery, providing superior repeatability and reliability compared to soft conductive materials that permanently deform and lose calibration over time.
Solution Approach 2:
The patent ensures continuous and repeatable pressure measurement through optical fibers that maintain their optical properties across multiple deformation cycles. Unlike conductive materials that degrade, the optical fibers provide consistent light transmission intensity changes, enabling long-term reliable monitoring with excellent measurement repeatability.
5Reliability
If conventional plantar pressure sensors use capacitive pressure sensing with dielectric material deformation, then pressure tracking is achieved, but recovery speed is unsatisfactory and results are not repeatable
Solution Approach 1:
The patent replaces capacitive sensing based on dielectric material deformation with optical fiber sensing. Optical fibers respond instantaneously to deformation and recover equally quickly, providing fast recovery speed and repeatable results. The optical sensing mechanism eliminates the slow relaxation characteristics of deformed dielectric materials.
6Reliability
If conventional plantar pressure sensors use bulky data collector units mounted around ankles with transmitters around waist, then data collection functionality is achieved, but natural movements such as foot rotation and center of mass changes are restricted
Solution Approach 1:
The patent extracts the heavy data collector units and waist transmitters from the wearable system, relying on the inherent immunity of optical fibers to electromagnetic interference. This eliminates bulky components that restrict natural movements, allowing free foot rotation and center of mass changes while maintaining full data collection functionality through the lightweight optical fiber network.
Solution Approach 2:
The patent replaces expensive, bulky electronic data collection systems with simple, lightweight optical fiber sensing. The optical fibers themselves are inexpensive and can be easily replaced if needed, eliminating the need for complex electronic hardware that restricts movement. The system achieves full functionality with minimal wearable components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The sensor offers reliable, repeatable, and comfortable plantar pressure monitoring, immune to electromagnetic interference, suitable for daily use in diagnosing and monitoring health issues, and adaptable to various applications.
Implementation Method 1
one or more light sources, each of the stretchable optical fibers being connected to at least one of the light sources; one or more light detectors each connected to at least one of the stretchable optical fibers and each configured to receive light signals emitted from the one or more light sources and transmitted by the stretchable optical fibers
Implementation Method 2
A deformation of a fiber causes a change in the light being transmitted by the fiber when the fiber is proximate to the location of the applied force. The deformation causes a defect such as a compression, a bend, a crease, or a dent, that decreases or alters an intensity or duration of the transmitted light.
Data Source
AI summary
A stretchable fiber optic pressure sensor is a sensing device that uses stretchable optical fibers that deform in response to an applied force. A deformation of a fiber causes a decrease in an intensity or alters a duration of the transmitted light due to a bend, crease, or dent in the fiber. The sensor may be configured to determine a pressure or force as applied by an appendage of a user. Multiple sensors may be configured to be in contact with multiple appendages, such as insoles inserted in shoes to determine walking attributes such as a gait, posture, pace, toe-walking, limping, stumbling, foot drop, swaying, or shuffling of a user. The sensor is configurable to transmit data associated with the applied pressure or force to a user's mobile device or computer to monitor or diagnose health issues associated with walking attributes determined through the use of the sensor.