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, due to the high nonlinearity and specialized fabrication requirements of these systems.
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 control systems.
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 and deformations
Solution Approach 1:
The patent uses flexible optical waveguides made from elastomeric materials that can withstand large strains and deformations while maintaining optical signal transmission. These waveguides are embedded within the soft actuator structure, allowing them to deform with the actuator while still providing accurate curvature measurements through changes in light propagation.
Solution Approach 2:
The patent replaces traditional mechanical curvature sensors with an optical sensing system. By using optical waveguides and measuring changes in light transmission, reflection, or emission based on actuator deformation, the system achieves curvature sensing without mechanical components that would fail under large strains.
2Loss of energy
If reflective metal coating is applied to waveguide walls, then light confinement is improved, but micro-cracks form during deformation causing light loss
Solution Approach 1:
The patent replaces rigid reflective metal coatings with flexible dielectric coatings or relies on the elastomeric waveguide structure itself to provide optical confinement. These flexible structures can deform with the actuator without developing micro-cracks, maintaining both light confinement and reliability under large strains.
Solution Approach 2:
The patent uses composite elastomeric materials with different refractive indices to create the waveguide structure. The core elastomer provides mechanical flexibility and strain tolerance, while the cladding elastomer with different refractive index provides optical confinement, eliminating the need for brittle metal coatings.
3Measurement precision
If lossy elastomer materials are used in waveguides, then sensitivity to deformation is improved, but light transmission is reduced
Solution Approach 1:
The patent optimizes the optical and mechanical properties of the elastomer materials by adjusting parameters such as refractive index, absorption coefficient, and elastic modulus. By carefully selecting and tuning these material parameters, the waveguide achieves sufficient light transmission while maintaining high sensitivity to deformation through controlled light loss mechanisms.
Solution Approach 2:
The patent uses the light loss in the waveguide as a feedback signal proportional to the actuator deformation. By measuring the change in light intensity or transmission through the waveguide, the system obtains real-time information about curvature and strain, enabling accurate sensing despite the inherently lossy nature of the elastomer material.
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 reliable, accurate, and cost-effective strain and curvature sensing capabilities, enabling advanced control and feedback systems for soft robotics, including hand orthotics and prosthetics, with high sensitivity and repeatability, while being compatible with the large strains and deformations of fluidically-powered actuators.
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, which are intentionally lossy and can be used as sensors to measure deformation by tracking light loss
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 sensors, 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.