Variable Stiffness Shaft Using Electroactive Polymer Actuation
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Solution Overview
Problem
Medical devices face challenges in achieving a balance between flexibility and strength, as increased flexibility often comes at the expense of reduced strength, and vice versa, and this optimal balance can vary by patient and procedure conditions.
Innovation Solution
Incorporating a hypotube with slots and an electroactive polymer sleeve that allows for adjustable compressive strength through the use of slots and electroactive polymers, which can be activated to increase stiffness by ion insertion or exclusion, enabling real-time adjustment of the device's performance parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the shaft is made stiffer to increase compressive strength, then strength is improved, but flexibility deteriorates
Solution Approach 1:
The shaft incorporates adjustable stiffness mechanisms including expandable rings, slots with electroactive polymer actuators, and reconfigurable internal structures that allow the shaft to dynamically change its rigidity level. This enables the shaft to adapt its mechanical properties during use, resolving the contradiction between needing high compressive strength and maintaining flexibility for navigation through vasculature.
Solution Approach 2:
The invention changes the physical parameters of the shaft by using electroactive polymers that alter their volume and stiffness in response to electrical signals, and by incorporating expandable structures that can change their configuration. These parameter changes allow the shaft to transition between flexible and stiff states, simultaneously satisfying both flexibility and strength requirements.
2Ease of operation
If the shaft is made more flexible to improve ease of navigation, then flexibility is improved, but compressive strength deteriorates
Solution Approach 1:
The shaft uses dynamic structures such as collapsible and expandable rings, and reconfigurable internal frameworks that can be adjusted during the procedure. The shaft starts flexible for navigation and can be stiffened when needed for device deployment or when encountering resistant vasculature, thus resolving the contradiction between flexibility and compressive strength.
Solution Approach 2:
The shaft is divided into multiple segments with different mechanical properties and adjustable connections. This segmentation allows different portions of the shaft to have different stiffness levels, enabling the proximal portion to be stiffer for strength while the distal portion remains flexible for navigation, or vice versa depending on procedural needs.
3Adaptability or versatility
If adjustable stiffness mechanisms are added to the shaft, then adaptability is improved, but device complexity increases
Solution Approach 1:
The shaft incorporates nested structures where expandable rings, internal reinforcement elements, and electroactive polymer actuators are contained within the existing shaft architecture. This nesting approach allows the shaft to gain adjustability features while minimizing additional external complexity, as the new functionalities are integrated within the existing structural envelope.
Solution Approach 2:
The shaft integrates multiple functions into unified structures, such as using electroactive polymer actuators that serve both as structural reinforcement elements and as actuation mechanisms, and designing internal frameworks that provide both structural support and adjustment capabilities. This multi-functionality reduces the need for separate dedicated components, thereby limiting the increase in overall device complexity.
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
Enables medical devices to be dynamically adjusted for optimal flexibility and strength during procedures, accommodating individual patient needs and varying vasculature conditions, thereby improving procedural efficacy and safety.
Implementation Method 1
an electroactive polymer sleeve that is disposed over the hypotube... An electroactive polymer is disposed on at least one of the first wall and the second wall... which can be activated to increase stiffness by ion insertion or exclusion
Data Source
AI summary
Medical devices may include structure or provision that permit a physician or other health care professional to adjust particular parameters such as flexibility, stiffness and compressive strength of at least a portion of the medical device. In some instances, the medical device may be adjusted prior to inserting the medical device into a patient. In some cases, the medical device may be adjusted while in use within the patient.