Magnetic Sensor Protective Layer Surface Roughness
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Solution Overview
Problem
Conventional biosensors face challenges in accurately detecting biomolecules due to variance in detection results, especially when dealing with samples of low biomolecule concentration, as a portion of captured biomolecules and magnetic beads are removed during the detection process.
Innovation Solution
A magnetic sensor with a substrate and a magnetoresistive effect element, where the protective layer on top of the magnetoresistive effect element has a prescribed surface roughness, aiding in the accurate detection of biomolecules using magnetic beads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional biosensor with a smooth protective layer is used, then the device structure is simple and easy to manufacture, but biomolecules and magnetic beads are removed during detection, causing large variance in detection results
Solution Approach 1:
The protective layer is designed with different surface properties: the first surface (facing the sample) has higher roughness (Ra: 0.1-10 nm) to prevent removal of biomolecules and magnetic beads, while the second surface (facing the magnetoresistive effect element) remains smooth to maintain device functionality. This local differentiation resolves the contradiction by providing both high detection accuracy and manageable device complexity.
2Reliability
If gradient magnetic field or washing is applied to remove excess biomolecules and magnetic beads, then unbound substances are cleared, but captured biomolecules and magnetic beads are also partially removed, increasing detection result variance
Solution Approach 1:
The protective layer's first surface is pre-engineered with specific roughness (Ra: 0.1-10 nm) to create strong adhesion sites that prevent the removal of captured biomolecules and magnetic beads during subsequent washing or gradient magnetic field application. This preliminary structural preparation counteracts the harmful effect of substance loss during the detection process.
3Measurement precision
If the protective layer surface is made rough to prevent removal of biomolecules, then detection accuracy improves, but the manufacturing process becomes more complex
Solution Approach 1:
The protective layer's surface roughness parameter is optimized to a specific range (Ra: 0.1-10 nm) that provides sufficient adhesion to prevent biomolecule removal while remaining compatible with conventional manufacturing techniques such as spin coating or dip coating. This parameter optimization resolves the contradiction by achieving high detection accuracy without excessively complicating the manufacturing process.
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 magnetic sensor achieves high accuracy in detecting biomolecules by minimizing the removal of biomolecules and magnetic beads, thereby reducing variance in detection results, even with low biomolecule concentrations.
Implementation Method 1
a magnetoresistive effect element provided on the first surface of the substrate. The resistance of the magnetoresistive effect element changes in accordance with an input magnetic field
Data Source
AI summary
A magnetic sensor used to detect a detection target substance in a sample includes a substrate having a first surface and a second surface, which is opposite the first surface and a magnetoresistive effect element provided on the first surface of the substrate. The resistance of the magnetoresistive effect element changes in accordance with an input magnetic field. A protective layer covers the top of the magnetoresistive effect element. The surface of the protective layer, which is positioned on top of the magnetoresistive effect element, has a prescribed surface roughness.