High Aspect Ratio Microelectrode Arrays with Tapered Tips

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Solution Overview

Problem

Conventional electrode formation processes are unable to produce satisfactory microelectrodes with lengths extended beyond 1.5 to 2 mm, resulting in fragile needles unsuitable for implantation due to severe narrowing or missing tips, limiting the ability to probe and stimulate neurons in complex three-dimensional environments.

Innovation Solution

A method involving electrical discharge machining to form a criss-cross pattern of channels on a substrate, followed by etching to create tapered tips with high aspect ratios, allowing for customizable lengths and enhanced mechanical strength of microelectrodes, which can be used as neural interface devices or cortical implants.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If conventional electrode formation processes are used to extend electrode lengths beyond 1.5 to 2 mm, then the length of microelectrodes is increased, but the mechanical strength deteriorates resulting in fragile needles unsuitable for implantation

Engineering Contradiction:

Improvelength of microelectrodeVSAvoidmechanical strength of microelectrode

Core Design Contradiction:

Length of moving objectVSStrength

Solution Approach 1:

The patent applies preliminary action by forming a tapered profile at the tip region of the microelectrode before the final etching process. This pre-formed taper reduces stress concentration during subsequent processing and implantation, preventing tip fracture while maintaining the ability to achieve extended lengths beyond 2 mm. The tapered geometry is created in advance to prepare the structure for successful long-term implantation.

Inventive Principle:

Principle #10Preliminary action

2Length of moving object

If conventional electrode formation processes are used to extend electrode lengths, then the length of microelectrodes is increased, but the manufacturing precision deteriorates resulting in severe narrowing or missing tips

Engineering Contradiction:

Improvelength of microelectrodeVSAvoidprecision of electrode tip formation

Core Design Contradiction:

Length of moving objectVSManufacturing precision

Solution Approach 1:

The tapered profile is formed as a preliminary structure before final tip definition through etching. This pre-shaping ensures that even when electrodes are extended to lengths beyond 2 mm, the tip region maintains proper geometry without severe narrowing or complete tip loss, thereby preserving manufacturing precision across extended length ranges.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent employs parameter changes by modifying the etching process parameters and utilizing a pre-formed tapered profile to maintain tip precision. By changing the geometric parameters (taper angle, tip radius) and process parameters (etching conditions), the method achieves consistent tip formation precision even for electrodes with lengths exceeding conventional limits of 1.5 to 2 mm.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If conventional electrode formation processes are used, then the manufacturing process is simple, but the adaptability deteriorates limiting the ability to probe and stimulate neurons in complex three-dimensional environments

Engineering Contradiction:

Improvesimplicity of fabrication processVSAvoidadaptability to three-dimensional environments

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The patent maintains ease of manufacture by using standard semiconductor fabrication processes while changing the geometric parameters to create tapered profiles. This parameter modification enables the electrodes to achieve high aspect ratios and extended lengths, providing the adaptability needed for complex three-dimensional neural environments without requiring entirely new manufacturing approaches.

Inventive Principle:

Principle #35Parameter changes

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

Enables the fabrication of ultra-high aspect ratio microelectrodes with customizable lengths, providing mechanical strength and suitability for implantation, enabling deeper access and complete coverage of nerves for recording and stimulating applications.

Implementation Method 1

A substantially criss-cross pattern of channels on a top surface of the work-piece substrate is formed using electrical discharge machining to form a plurality of shaped columns having tapered tips

Methodology Applied

Scientific EffectElectrical discharge machining: Electrical Discharge Machining

Implementation Method 2

The plurality of shaped columns is etched to sharpen the tapered tips into needle tips forming the array of microelectrodes

Methodology Applied

Scientific EffectEtching:

Data Source

PatentUS8886279B2High aspect ratio microelectrode arrays enabled to have customizable lengths and methods of making the same

Publication Date: 2014.11.11 UNIV OF UTAH RES FOUND

AI summary

A method of fabricating an array of micro electrodes enabled to have customizable lengths. A substantially criss-cross pattern of channels on a top surface of the work-piece substrate (10) is formed using electrical discharge machining to form a plurality of shaped columns (20) having tapered profiles. The shaped columns have a tapering profile which extends at least 50% of the length of the columns. The plurality of shaped columns is etched to sharpen the tapered tips into needle tips forming the array of microelectrodes.