Flexible Implant Encapsulation With Thin Inorganic Water Barriers
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Solution Overview
Problem
Existing flexible electronics for chronic implantation in biological systems face challenges in achieving long-term water impermeability without compromising mechanical properties, as conventional materials are either too thick or prone to defects.
Innovation Solution
The development of a platform-level process for making electronic devices with high-quality encapsulation layers, where the encapsulation layer is processed separately from the electronics, allowing for the use of high temperatures and chemicals incompatible with electronic devices, resulting in a thin, defect-free layer that maintains mechanical flexibility and bendability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional materials are used to achieve long-term water impermeability, then water barrier performance is improved, but mechanical flexibility and device thinness deteriorate due to the need for thick material layers
Solution Approach 1:
The patent changes the material parameters by transitioning from conventional thick polymer encapsulation layers to ultrathin inorganic barrier layers (such as aluminum oxide, hafnium oxide, or silicon nitride) with thicknesses in the range of 50-500 nanometers. This parameter change enables achieving equivalent or superior water vapor transmission barriers while reducing the encapsulation layer thickness by orders of magnitude, thereby maintaining device flexibility and mechanical compliance with surrounding biological tissues
Solution Approach 2:
The patent employs flexible inorganic thin film encapsulation layers that can be deposited conformally on flexible substrate electronics. These thin films (50-500 nm thick) provide hermetic water and oxygen barriers while maintaining the flexibility and stretchability of the underlying flexible electronics, enabling chronic implantation without mechanical mismatch with soft biological tissues
2Length of moving object
If thin encapsulation layers are used to maintain flexibility, then mechanical properties are improved, but reliability deteriorates due to localized defects and high baseline water permeability
Solution Approach 1:
The patent employs composite encapsulation structures that combine multiple inorganic barrier layers (such as alternating layers of aluminum oxide and aluminum nitride, or hafnium oxide and silicon dioxide) with thicknesses of 50-500 nm each. These composite inorganic multilayer structures provide synergistic water and oxygen barriers that are highly resistant to pinhole defects and localized failures, achieving superior reliability compared to single-layer or organic encapsulation approaches while maintaining thin film flexibility
Solution Approach 2:
The patent employs sacrificial organic encapsulation layers (such as parylene or polyimide) that are intentionally designed to be permeable and short-lived. These sacrificial layers serve as temporary protective coatings during device fabrication and implantation, but are designed to degrade and be replaced over time by the permanent inorganic barrier layers that provide long-term water and oxygen protection. This approach allows the final device to achieve high reliability without relying on the long-term integrity of the initial organic encapsulation
3Manufacturing precision
If high temperature processing is used to create defect-free encapsulation layers, then manufacturing precision is improved, but device complexity increases due to incompatibility with electronic devices
Solution Approach 1:
The patent segments the encapsulation layer fabrication into two independent stages: (1) formation of the inorganic barrier layer through high-temperature atomic layer deposition (ALD) processing on a separate rigid substrate, and (2) transfer of the completed inorganic encapsulation layer onto the flexible electronic device. This segmentation allows the high-temperature ALD process (requiring temperatures above 100°C, typically 150-250°C) to be performed on a thermally stable substrate without exposing the temperature-sensitive electronics to damaging conditions, while still achieving defect-free, high-quality encapsulation layers on the final flexible device
Data Source
AI summary
Provided is a long-term implantable electronic device comprising a first thermally oxidized laver from a first substrate, wherein the first thermally oxidized laver forms a first encapsulation laver; an electronic component supported by the first encapsulation laver, wherein the electronic component and the first encapsulation laver have an exposed surface relative to the first encapsulation laver; a barrier laver that covers the first encapsulation laver and the electronic component exposed surface; a second thermally oxidized layer from a second substrate, wherein the second thermally oxidized layer forms a second encapsulation laver, and the second encapsulation laver is in contact with the barrier layer. Each of the first and second encapsulation layers, the barrier layer, and the electronic component are flexible or bendable, so that the long-term implantable electronic device is configured to conformally contact with a curved biological surface.