Flexible Circuit Electrode Array Retinal Adhesion
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Solution Overview
Problem
Existing flexible circuit electrode arrays for biomedical implants, such as retinal prostheses, face challenges in achieving optimal adhesion and insulation between polymer layers, leading to increased electrical resistance and potential damage to delicate neural tissue due to sharp edges and uneven pressure distribution on curved surfaces like the retina.
Innovation Solution
A flexible circuit electrode array is manufactured using a method that involves depositing a metal trace layer with a base and top coating layer, activating the insulator polymer base layer, and applying a top insulator polymer layer to form a single insulating polymer layer, with a top metal layer acting as an adhesion aid, and shaping the array to match the curvature of the retina using thermoplastic polymers and molds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a flexible circuit electrode array is made flat using conventional fabrication techniques, then manufacturing precision is improved, but pressure distribution on curved retinal surface deteriorates causing tissue damage
Solution Approach 1:
The patent applies curvature to the flexible circuit electrode array to match the spherical surface of the retina. The array is formed with a curved configuration that conforms to the retinal surface, eliminating sharp edges and ensuring uniform pressure distribution across all electrodes during implantation.
2Device complexity
If polymer layers are stacked without activation treatment, then manufacturing complexity is reduced, but adhesion between layers deteriorates leading to delamination
Solution Approach 1:
The patent applies activation treatment to the first polymer layer before depositing the second polymer layer. This preliminary activation creates a surface that promotes strong adhesion between the layers, preventing delamination during implantation and operation.
3Strength
If edges of the flexible circuit are left sharp for structural integrity, then mechanical strength is improved, but harmful factors increase due to cutting of delicate retinal tissue
Solution Approach 1:
The patent curves the flexible circuit electrode array to match the retinal surface, which inherently rounds all edges and eliminates sharp corners that could cut retinal tissue during implantation, while maintaining structural integrity through the curved configuration.
4Device complexity
If a single flat layer is used for simplicity, then device complexity is reduced, but insulation performance deteriorates due to uneven pressure distribution on curved surfaces
Solution Approach 1:
The patent forms the flexible circuit electrode array with a curved configuration that conforms to the spherical retinal surface. This curvature ensures that all electrodes maintain uniform contact pressure with the retina, providing consistent insulation performance across the entire array during implantation.
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 method enhances adhesion and insulation properties, reducing electrical resistance and minimizing tissue damage by ensuring uniform pressure distribution and smooth edges, thus improving the performance and safety of the implantable device.
Implementation Method 1
a top metal layer acting as an adhesion aid
Implementation Method 2
shaping the array to match the curvature of the retina using thermoplastic polymers and molds
Data Source
AI summary
A method for manufacturing a flexible circuit electrode array, comprising:a) depositing a metal trace layer containing a base coating layer, a conducting layer and a top coating layer on the insulator polymer base layer;b) applying a layer of photoresist on the metal trace layer and patterning the metal trace layer and forming metal traces on the insulator polymer base layer;c) activating the insulator polymer base layer and depositing a top insulator polymer layer and forming one single insulating polymer layer with the base insulator polymer layer;d) applying a thin metal layer and a layer of photoresist on the surface of the insulator polymer layer and selective etching the insulator layer and the top coating layer to obtain at least one via; ande) filling the via with electrode material.A layer of polymer is laid down. A layer of metal is applied to the polymer and patterned to create electrodes and leads for those electrodes. A second layer of polymer is applied over the metal layer and patterned to leave openings for the electrodes, or openings are created later by means such as laser ablation. Hence the array and its supply cable are formed of a single body. Alternatively, multiple alternating layers of metal and polymer may be applied to obtain more metal traces within a given width.The method provides an excellent adhesion between the polymer base layer and the polymer top layer and insulation of the trace metals and electrodes.