Multi-Material Housing Seals for Waterproof Physiological Monitors
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Solution Overview
Problem
Creating a waterproof enclosure for wearable physiological monitors is challenging due to materials with different thermal expansion coefficients and poor inter-material bonding, leading to separation and potential skin irritation.
Innovation Solution
A multi-part housing assembly using a first part made of a conductive material with anchors, a second part with a support structure, and a third part chemically bonded to the second part, forming a waterproof seal without adhesives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If insert molding is used to join plastic and metal parts, then the assembly process is simplified, but the seal is insufficient for waterproofing
Solution Approach 1:
A third part made of elastomeric material is introduced as an intermediary between the metal first part and plastic second part. This third part chemically bonds to the plastic and mechanically secures the metal, creating a reliable waterproof seal that insert molding alone cannot achieve.
Solution Approach 2:
The housing assembly uses composite materials with different properties: metal for conductivity and structural strength, plastic for molding flexibility, and elastomeric material for sealing and bonding. This multi-material composite approach resolves the contradiction between ease of manufacture and waterproof reliability.
2Reliability
If gluing or taping is used to join different materials, then the seal may be improved, but gaps and other undesirable effects occur
Solution Approach 1:
The patent replaces mechanical joining methods (gluing, taping) with chemical bonding. The third part chemically bonds to the plastic second part, creating a stronger, more reliable connection without the gaps and defects associated with adhesive methods.
Solution Approach 2:
Different joining methods are used at different locations: chemical bonding between the third part and plastic, and mechanical securing of the metal first part. This localized application of different bonding mechanisms eliminates the need for uniform gluing or taping that causes gaps and defects.
3Adaptability or versatility
If different materials are used for housing parts, then design flexibility is improved, but material separation occurs due to different coefficients of thermal expansion
Solution Approach 1:
The patent accounts for thermal expansion parameter differences by using the elastomeric third part as a buffer between metal and plastic components. This material can accommodate dimensional changes due to thermal expansion without causing separation, maintaining structural integrity across temperature variations.
Solution Approach 2:
The use of composite materials with complementary properties allows different thermal expansion coefficients to coexist without causing separation. The elastomeric material acts as a compliant interface that absorbs thermal stress, enabling design flexibility while preventing material separation.
4Ease of manufacture
If adhesive bonding is used to secure different materials, then assembly is simplified, but skin irritation may occur
Solution Approach 1:
The patent replaces adhesive bonding with mechanical securing through the third part. The elastomeric material mechanically locks the metal first part to the plastic second part without requiring adhesives, thereby eliminating the skin irritation problem while maintaining assembly simplicity.
Solution Approach 2:
The third part serves as an intermediary that eliminates the need for skin-contacting adhesives. By providing mechanical securing through the elastomeric material, the harmful adhesive substances are removed from the device structure, preventing skin irritation.
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 assembly provides a durable, waterproof enclosure that maintains structural integrity and prevents material separation, ensuring reliable device function in various environments.
Implementation Method 1
a third part that can be chemically bonded to the second part may secure the first part by filling a volume between the anchor of the first part and an adjacent surface of the second part around the opening. In some aspects, the chemical bond between the second part and the third part creates an environmental seal around the opening.
Data Source
AI summary
An enclosure for an electronic device, such as a wearable physiological monitor, may be formed of at least two different materials, e.g., a first part formed of a first material (e.g., a metal) and a second part formed of a second material (e.g., a plastic). The second part may include an opening to receive at least a portion of the first part therein, where the first part includes an anchor projecting from a surface thereof into the opening of the second part. To ensure that the enclosure is waterproof, a third part that can be chemically bonded to the second part may secure the first part by filling a volume between the anchor of the first part and an adjacent surface of the second part around the opening. In some aspects, the chemical bond between the second part and the third part creates an environmental seal around the opening.