Microelectrode Array Bonding Using Biocompatible Solder
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Solution Overview
Problem
Fabricating high density microelectrode arrays with flexible microwires for neural interfaces poses challenges such as material machining, fixturing, damage reduction, hermeticity, and fluid/ion transfer during fabrication.
Innovation Solution
A microelectrode array with elongated microwires bonded to a substrate using biocompatible solder or braze material, featuring a ceramic substrate and conical tips, and methods involving diffusion bonding, ultrasonic bonding, and subtractive techniques to form microwires without affecting hermeticity, with a ceramic film coating for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If flexible microwires are used in high density microelectrode arrays, then adaptability to brain tissue is improved, but fabrication complexity and damage risk increase
Solution Approach 1:
The device is segmented into distinct functional modules: a rigid substrate containing feedthroughs and bonding structures, and flexible microwire probes extending from it. This segmentation allows the substrate to provide structural stability during fabrication while the microwires provide flexibility for brain tissue adaptation, resolving the contradiction between adaptability and fabrication complexity.
Solution Approach 2:
The substrate is pre-fabricated with feedthroughs, bonding pads, and hermetic sealing structures before the microwires are attached. This preliminary action ensures that all complex fabrication steps (machining, hermetic sealing, electrical interconnections) are completed on the rigid substrate first, simplifying subsequent micrawire attachment and reducing overall fabrication complexity while maintaining adaptability.
2Reliability
If hermetic sealing is implemented during fabrication, then reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The hermetic sealing function is merged with the substrate structure itself through integrated feedthroughs and bonding designs. The substrate incorporates hermetic feedthroughs that pass through it, and bonding structures that create hermetic seals between the substrate and micrawires, eliminating the need for separate hermetic sealing components and reducing manufacturing complexity while ensuring reliability.
Solution Approach 2:
Biocompatible solder or braze materials serve as intermediary substances that simultaneously achieve hermetic sealing and electrical connection between the substrate feedthroughs and micrawires. This intermediary material resolves the contradiction by providing both hermeticity for reliability and a manufacturable bonding process.
3Length of moving object
If micrawires are machined with small diameters, then insertion capability is improved, but susceptibility to damage increases
Solution Approach 1:
The flexible micrawires are nested within or attached to the rigid substrate structure during fabrication and handling. The substrate acts as a protective housing that shields the delicate micrawires from damage during the fabrication process, allowing the micrawires to have small diameters for brain tissue insertion while the substrate provides mechanical strength and damage resistance.
Solution Approach 2:
The rigid substrate provides beforehand cushioning and mechanical support to the flexible micrawires during fabrication and implantation. This protective structure prevents damage to the delicate micrawires before they are inserted into brain tissue, resolving the contradiction between small diameter for insertion capability and strength for damage resistance.
4Quantity of substance
If high density arrangement is implemented, then recording capability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The rigid substrate serves multiple functions: it provides structural support, establishes precise positioning for high-density micrawire arrays through pre-fabricated feedthroughs and bonding pads, and enables hermetic sealing. This multi-functionality allows high-density arrangement for improved recording capability while the substrate's precision manufacturing capabilities maintain positioning accuracy.
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 solution enables the creation of implantable neural-interface probes with improved hermeticity, reduced damage, and effective insertion into brain tissue, facilitating better neuronal recording and stimulation while maintaining structural integrity.
Implementation Method 1
an array of microwires extending from the substrate, wherein the array of microwires may be connected or bonded to the plurality of feedthroughs using a biocompatible solder or braze material
Implementation Method 2
an array of microwires extending from the substrate, wherein the array of microwires may be connected or bonded to the plurality of feedthroughs using a biocompatible solder or braze material
Implementation Method 3
the device may further comprise a ceramic film coated over or onto the array of micrawires
Data Source
AI summary
An implantable device and methods for forming the same are provided. The device may comprise: (a) a substrate comprising a plurality of feedthroughs, wherein the plurality of feedthroughs comprises a first conductive material; and (b) an array of microwires extending from the substrate. The array of microwires may be connected or bonded to the plurality of feedthroughs using a biocompatible solder or braze material or intermediate filler material. The array of microwires may comprise a second conductive material that is different from the first conductive material.