Quasi-Digital MR Biosensor Array for Single Molecule Detection
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Solution Overview
Problem
Current biosensor technologies are unable to detect single molecules effectively due to limitations in sensitivity and practicality, particularly in clinical and field settings, as they require large numbers of magnetic nanoparticles and precise calibration, which is not feasible with existing magnetoresistive (MR) sensors.
Innovation Solution
A quasi-digital magnetoresistive biosensor system comprising an array of small MR sensors linked together, enabling enhanced sensitivity through a digital readout and eliminating the need for precise resistance measurements, allowing for the detection of a single magnetic nanoparticle using less expensive and robust electronics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If large MR sensors are used to detect single molecules, then sensitivity is improved, but device complexity and manufacturing difficulty increase due to requiring hundreds to thousands of magnetic nanoparticles and meticulous calibration
Solution Approach 1:
The patent divides the detection function across multiple small MR sensors arranged in an array, where each sensor detects individual magnetic nanoparticles. This segmentation allows the system to achieve high sensitivity through statistical accumulation of signals from many independent sensors, eliminating the need for a single large sensor with complex calibration requirements.
Solution Approach 2:
The patent uses multiple copies of identical small MR sensors in an array configuration. Each sensor is a simple, standardized unit that can be mass-produced, and the collective signal from these copies provides the necessary sensitivity. This copying approach replaces the need for a single complex, meticulously calibrated large sensor.
2Device complexity
If small MR sensors are used to detect single molecules, then device complexity is reduced, but the probability of a molecule or reporter landing on a single tiny sensor becomes approximately zero
Solution Approach 1:
The patent merges the detection capabilities of multiple small MR sensors into a single array that functions as one detection system. By combining the signals from many sensors, the system achieves both the simplicity of small sensors and the high detection probability of a large effective sensing area, resolving the trade-off between sensor size and detection probability.
3Ease of operation
If fluorescent labels are used for detection, then ease of operation is improved, but sensitivity to detect single molecules is insufficient due to photobleaching and autofluorescence
Solution Approach 1:
The patent replaces the optical detection mechanism (fluorescent labels) with a magnetic detection mechanism (MR sensors). This substitution eliminates the fundamental limitations of fluorescence (photobleaching, autofluorescence) while maintaining ease of operation through simple resistance measurements. The magnetic field interaction with MR sensors provides inherently higher sensitivity for single-molecule detection.
4Measurement precision
If Wheatstone bridge is used for precise resistance measurements, then measurement precision is improved, but device complexity and susceptibility to thermal drift increase
Solution Approach 1:
The patent extracts and removes the Wheatstone bridge circuitry from the detection system. Instead of using complex bridge measurements, the invention directly measures resistance changes of individual small MR sensors, eliminating the need for bridge balancing and reducing susceptibility to thermal drift. This simplification maintains measurement precision while significantly reducing device complexity.
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 system achieves competitive or better sensitivity in detecting single molecules with reduced complexity and noise, overcoming the limitations of existing MR sensors by using an array configuration and digital detection methods, making it suitable for practical applications.
Implementation Method 1
magnetoresistive (MR) sensors... The change in resistance of an MR sensor is proportional to the coverage of MNPs on the sensor's surface
Implementation Method 2
magnetic layers... The magnetic layers may be ferromagnetic, antiferromagnetic, synthetic antiferromagnetic or a combination thereof
Data Source
AI summary
A biosensor may provide a magnetoresistive (MR) film comprising a nonmagnetic layer may be sandwiched between the two ferromagnetic layers. The MR film may be positioned on a substrate, where the edges of the MR film are in contact with leads. The leads may be in contact with pads. The sensors may provide quasi-digital readout that enable greatly enhanced sensitivity. In some embodiments, biosensors may be arranged as array of sensors. The array of sensors may be arranged as a symmetric or asymmetric N1×N2 array, where N1 and N2 are integers, N1 represents the number of sensors linked together in series, and N2 represents the number of sensor sets in parallel, where each sensor set may comprise one or more sensors. Further, the array of sensors may be coupled to a voltmeter, which may be a single voltmeter in that allows the sensors to all be probed simultaneously.