Soot Sensor Inter-Digitized Electrode Ablation
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Solution Overview
Problem
Existing soot sensors face challenges in maximizing signal sensitivity and protecting electrodes from abrasion in exhaust environments, as the inter-digitized finger design is prone to carbon shorts and requires effective pattern formation and protection methods.
Innovation Solution
A method involving the use of an ablating device to create inter-digitized finger paths on a conductive sensing element pad without electrical connections, which can be formed before or after ink firing, with a protective layer to ensure soot contact and prevent electrode shorting, and the option to laminate a heater for enhanced functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If inter-digitized finger paths are created to maximize perimeter between electrodes, then sensitivity of soot detection is improved, but the risk of carbon shorts between fingers increases
Solution Approach 1:
An electrically insulating material is introduced as an intermediary substance between the conductive finger paths. This insulating material prevents carbon shorts while allowing the inter-digitized structure to maintain its high perimeter-to-area ratio, thus preserving sensitivity without compromising reliability.
Solution Approach 2:
The insulating material is applied selectively in the regions between finger paths where shorts would occur, while maintaining conductive properties in the finger paths themselves. This localized differentiation allows each region to have the appropriate electrical property for its function.
2Measurement precision
If electrode paths are made longer to maximize signal, then measurement precision is improved, but the electrodes become more vulnerable to abrasion from exhaust
Solution Approach 1:
A protective coating layer is applied over the conductive finger paths, creating a protective shell that shields the electrodes from abrasive exhaust particles while allowing the long inter-digitized structure to maintain its signal-generating capability.
Solution Approach 2:
The sensor structure combines conductive materials for the finger paths with insulating and protective coating materials, creating a composite structure that simultaneously achieves electrical functionality, mechanical protection, and chemical resistance.
3Strength
If protective coating is applied to prevent abrasion, then electrode protection is improved, but soot contact with electrodes may be reduced
Solution Approach 1:
The protective coating is designed with porous or permeable characteristics that allow soot particles to penetrate through or adhere to the coating while still providing mechanical protection. This maintains electrode protection while ensuring adequate soot contact for accurate measurement.
Solution Approach 2:
The protective coating properties are optimized locally - providing dense protection in areas prone to abrasion while maintaining permeability or soot-accessibility in areas where particle contact is critical for sensing.
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
This approach enhances signal sensitivity and protects electrodes by creating precise, long paths between conductive fingers, allowing for accurate soot measurement and prevention of large debris-induced shorts, thereby improving the reliability and accuracy of soot sensing.
Implementation Method 1
using an ablating device to establish two separate inter-digitized fingers paths without electrical connection between the finger paths
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
An ablating device is used to form a pattern (32) into a sensing element pad (28) of a soot sensor, with the pattern (32) establishing two finger paths (34, 36) without electrical connection between them. The pattern (32) can be formed through a protective layer (46) on the sensing element pad (28) before the sensing element pad (28) is fired.