Reusable PVDF Sensor with Polyurethane Encapsulation
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Solution Overview
Problem
Existing respiratory activity sensors, particularly those using PVDF film, are not reusable due to moisture permeation and lead wire detachment issues during cleaning, limiting their durability and effectiveness in repeated use.
Innovation Solution
A reusable sensor design featuring a PVDF film coated with conductive layers and lead wire tabs, sandwiched between double-sided adhesive tape and encapsulated in polyurethane layers for moisture-proofing, ensuring secure electrical connections and preventing lead pull-out.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sensor is designed for single-use application, then manufacturing complexity is reduced, but reliability and cost-effectiveness deteriorate due to inability to reuse
Solution Approach 1:
The sensor employs a nested layered construction where the PVDF film is sandwiched between adhesive layers, which are in turn enclosed within polyurethane encapsulation layers. This nested structure protects the sensitive electrical interface from moisture while maintaining a compact form factor, enabling reusable operation without proportionally increasing external dimensions.
Solution Approach 2:
The sensor utilizes a composite construction combining PVDF film (pyroelectric/piezoelectric material), conductive coatings, adhesive layers, and polyurethane encapsulation. Each material layer serves specific functions: PVDF for signal generation, conductive coating for electrical interface, adhesive for bonding, and polyurethane for moisture protection. This composite approach achieves reusability by integrating multiple protective and functional layers.
2Ease of manufacture
If the sensor construction uses layered design, then manufacturing is simplified, but moisture permeation occurs compromising electrical interface
Solution Approach 1:
The sensor employs thin film encapsulation using polyurethane material that conforms to the layered construction. This flexible film barrier effectively prevents moisture permeation to the electrical interface while maintaining the compact, lightweight characteristics of the thin-film PVDF sensor. The encapsulation layers are heat-sealed to create a hermetic barrier.
Solution Approach 2:
The combination of adhesive layers and polyurethane encapsulation creates a composite structure where each layer contributes specific properties: adhesive provides bonding strength, while polyurethane provides moisture barrier properties. This composite approach maintains ease of manufacture through layer-by-layer assembly while achieving reliable moisture protection.
3Device complexity
If lead wires are directly attached to PVDF film, then device complexity is reduced, but lead wire detachment occurs during cleaning
Solution Approach 1:
The sensor construction employs preliminary bonding actions where lead wires are first attached to metal tabs using conductive adhesive, then the entire assembly is encapsulated within polyurethane layers. This preliminary attachment sequence ensures lead wires are securely fixed before final encapsulation, preventing detachment during subsequent cleaning operations while maintaining relatively simple overall structure.
Solution Approach 2:
The lead attachment structure uses nested bonding where leads are attached to tabs, which are then enclosed within the encapsulation layers. This nested arrangement protects the lead connections from mechanical stress during cleaning while maintaining a compact integrated structure without requiring complex external mounting hardware.
4Reliability
If the sensor is made reusable with moisture protection, then reliability improves, but manufacturing complexity increases
Solution Approach 1:
The moisture protection is achieved using thin polyurethane film encapsulation layers that conform to the sensor construction. These flexible films provide effective moisture barriers while adding minimal complexity to the manufacturing process. The heat-sealing method for joining encapsulation layers is a standard industrial process that does not require specialized equipment.
Solution Approach 2:
The encapsulation structure is segmented into discrete layers (adhesive layers and polyurethane layers) that can be applied sequentially in the manufacturing process. This segmentation allows for systematic assembly where each layer serves a specific protective function, making the manufacturing process manageable despite the multi-layer 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
The design allows for reliable and repeated use of the sensor by preventing moisture ingress and ensuring secure lead connections, maintaining signal integrity during cleaning and reuse.
Implementation Method 1
The film has both pyroelectric and piezoelectric properties and, as such, is responsive to both temperature changes and physical vibration
Implementation Method 2
The film has both pyroelectric and piezoelectric properties and, as such, is responsive to both temperature changes and physical vibration
Implementation Method 3
The polyurethane layers extend beyond the perimeter edges of the double-sided tape and the edge portions of the polyurethane layers are heat sealed to one another to totally encapsulate the PVDF film, the lead tabs and the layers of double-sided adhesive tape in a moisture-proof manner
Data Source
AI summary
A sensor for use with a polysomnograph in a sleep lab setting is made reusable by laminating a PVDF film and associated lead contacts within a flexible, moisture-impervious plastic envelope that is hermetically sealed about its periphery. Lead terminals within the envelope are adhered to the metalized surfaces of the PVDP film using a conductive adhesive which inhibits dislodgement of the leads from the sensor even with rough handling and cleaning.