Elastomeric Waveguides for Soft Robotics Strain Sensing
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Solution Overview
Problem
Current soft robotics systems lack reliable, affordable, and easy-to-fabricate sensors for curvature and strain measurement, particularly in fluidically-powered actuators, which are essential for advanced control and feedback systems in wearable devices like hand orthotics and prosthetics.
Innovation Solution
The development of stretchable optical waveguides made from elastomeric materials with varying refractive indices, which are intentionally lossy and can be used as sensors to measure deformation by tracking light loss, allowing for accurate curvature and strain sensing without the need for external cameras or complex fabrication processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional rigid sensors are used in soft actuators, then measurement precision can be achieved, but the sensors cannot withstand large strains (>50%) and are incompatible with soft actuator deformation
Solution Approach 1:
The patent uses flexible optical waveguides made from elastomeric materials that can stretch and deform with the soft actuator. The waveguide core and cladding are both made from elastomers with different refractive indices, allowing the entire structure to be highly flexible and stretchable while maintaining optical guiding functionality during large deformations
Solution Approach 2:
The patent employs composite elastomeric materials with varying refractive indices to create the waveguide structure. The core elastomer has a higher refractive index than the cladding elastomer, enabling total internal reflection while both materials provide stretchability and flexibility to accommodate soft actuator deformation
2Loss of energy
If reflective metal coating is applied to waveguide walls to prevent light loss, then light confinement improves, but micro-cracks form during deformation causing light leakage and sensor noise
Solution Approach 1:
The patent eliminates rigid metal coatings and uses a fully elastomeric waveguide structure where both core and cladding are flexible. This allows the waveguide to stretch and deform without creating micro-cracks, maintaining reliable optical confinement throughout the actuator's range of motion
Solution Approach 2:
The patent changes the material parameters by using elastomeric materials with appropriate refractive index differences instead of rigid materials with metal coatings. This parameter change enables the waveguide to maintain optical functionality while accommodating large deformations without cracking
3Loss of energy
If expensive materials like gold are used for reflective coating, then light reflection efficiency improves, but manufacturing cost and process complexity increase
Solution Approach 1:
The patent uses a fully elastomeric waveguide structure that eliminates the need for expensive metal coatings like gold. The optical confinement is achieved through the refractive index difference between the core and cladding elastomers, which can be manufactured using simple injection molding processes
Solution Approach 2:
The patent replaces expensive, difficult-to-manufacture metal coatings with inexpensive elastomeric materials that can be easily molded. The elastomeric waveguide achieves sufficient optical confinement without requiring precious metals, dramatically reducing manufacturing cost and process complexity
4Device complexity
If open-loop control is used for soft actuators, then system simplicity is maintained, but control accuracy and repeatability are insufficient for sophisticated applications
Solution Approach 1:
The patent implements feedback control by using the stretchable optical waveguide as a sensor to measure actuator deformation in real-time. The photodetector detects light intensity changes caused by deformation, providing feedback signals that enable closed-loop control algorithms to achieve accurate and repeatable actuator positioning
Solution Approach 2:
The patent replaces complex mechanical encoders and external vision systems with an integrated optical sensing approach. The elastomeric waveguide directly measures deformation through optical intensity changes, providing a simpler yet more accurate sensing mechanism that works seamlessly with the soft actuator
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
These waveguides provide high sensitivity, repeatability, and precision in measuring curvature and strain, enabling advanced control systems for soft robotics and prosthetics, while being cost-effective and chemically stable, thus enhancing the functionality of wearable devices.
Implementation Method 1
Waveguides, such as light guides, can confine and guide waves. This can enable waves, such as optical waves, to be transported over a distance.
Implementation Method 2
stretchable optical waveguides made from elastomeric materials with varying refractive indices
Data Source
AI summary
Waveguides, such as light guides, made entirely of elastomeric material or with indents on an outer surface are disclosed. These improved waveguides can be used in scissors, soft robotics, or displays. For example, the waveguides can be used in a strain sensor, a curvature sensor, or a force sensor. In an instance, the waveguide can be used in a hand prosthetic. Sensors that use the disclosed waveguides and methods of manufacturing waveguides also are disclosed.