Fractal Interconnects for Retinal Implants
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Solution Overview
Problem
Current neuro-electronic interface devices face challenges such as capacitance overload, toxin induction, and insufficient connections between electrodes and neurons, limiting the functionality of electronic implants like retinal implants and prosthetic hands.
Innovation Solution
The development of fractal interconnects with scaling gradients between 1.1 and 1.9 over a scaling range of at least one order of magnitude, which are fabricated using nanoscale particles and deposited onto a non-conductive planar layer, providing improved connectivity and reduced charge density at the interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the size of each electrode is increased to improve connection likelihood with neurons, then connectivity to neurons is improved, but light transmission to the underlying photodiode is blocked
Solution Approach 1:
The electrode surface is transformed from a conventional flat 2D plane to a fractal 3D structure with dimension between 1 and 2. This dimensional transformation allows the electrode to occupy more spatial volume and provide greater surface area for neuronal contact while maintaining a smaller projected footprint, thereby preserving light transmission to the photodiode below.
Solution Approach 2:
The fractal electrode structure exhibits self-similarity across multiple scales, with smaller fractal patterns nested within larger ones. This nested architecture enables the electrode to maximize its surface area within a compact form factor, increasing neuronal connectivity without proportionally increasing the overall electrode size that would block light.
2Object-affected harmful factors
If the surface roughness of the electrode is increased to reduce capacitance overload and toxin induction, then electrical signal safety is improved, but manufacturing complexity increases
Solution Approach 1:
The electrode surface morphology is changed from conventional smooth or uniformly rough surfaces to a fractal structure with specific dimension between 1 and 2. This parameter change in surface geometry provides controlled surface area expansion that reduces charge density and electrical stress while maintaining manufacturability through established fractal fabrication techniques.
Solution Approach 2:
The fractal electrode can be constructed using composite material structures that combine conductive materials with fractal geometries. This allows the electrode to achieve the desired surface characteristics for reduced capacitance overload while utilizing materials and fabrication processes that are compatible with existing manufacturing capabilities.
3Productivity
If photodiodes are fabricated with high packing density to match retinal rod and cone density, then light detection capacity is improved, but the number of unconnected electrodes increases
Solution Approach 1:
By transforming the electrode from a 2D planar structure to a fractal structure with dimension between 1 and 2, the electrode achieves greater surface area within the same footprint. This allows high-density photodiode arrays to maintain their light detection capacity while their corresponding fractal electrodes provide sufficient surface area to connect with the high density of retinal neurons.
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 fractal interconnects enhance connectivity to neurons, allowing for more reliable and efficient signal transmission while minimizing damage to biological tissues, thereby improving the performance of neuro-electronic interfaces in various implant applications.
Implementation Method 1
The interconnect has a fractal dimension D between 1.4 and 1.9 over a scaling range of at least one order of magnitude below 200 μm... the interconnect consists of an assembly of nanoscale particles
Data Source
AI summary
A neuro-electronic interface device has a micro-electrode electrically connected to an interconnect that has scaling gradients between 1.1 and 1.9 over a scaling range of at least one order of magnitude. The device preferably has an array of such fractal interconnects in electrical contact with an array of micro-electrodes. Such fractal interconnect arrays may be components of implants including a retinal implant device having an array of photodetectors in electrical contact with the array of micro-electrodes. The interconnects may be fabricated by forming nanoscale particles and depositing them onto a non-conductive surface that is smooth except for electrodes which serve as nucleation sites for the formation of fractal interconnect structures through diffusion limited aggregation.