Capacitive Skin Sensing for Safe Needle Activation in Injection Devices
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Solution Overview
Problem
Existing injection devices lack adequate security measures to prevent accidental medication expulsion and user injury, particularly when the device is placed on hard surfaces or when handling, and fail to distinguish between human skin and other materials.
Innovation Solution
An injection device equipped with a capacitive proximity sensor featuring a concave electrode adjacent to the needle passage, which only detects human skin and prevents needle activation on non-skin surfaces, combined with a control unit that ensures the needle is only moved to the operating position when proper skin contact is confirmed, reducing the risk of accidental injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitive proximity sensor is used to detect skin contact, then the ability to detect proximity is improved, but the sensor may falsely detect non-skin materials (hard surfaces, clothes, etc.) leading to accidental needle activation
Solution Approach 1:
The electrode is configured with a specific geometric shape (e.g., annular, U-shaped) that matches the contour of the through hole. This local geometric configuration creates an electric field distribution that is sensitive to skin contact at the through hole location while being less sensitive to other materials, thereby improving detection accuracy and reducing false positives
Solution Approach 2:
The sensor parameters (electrode geometry, capacitance thresholds, detection sensitivity) are specifically calibrated to distinguish skin from non-skin materials. By adjusting these parameters, the system achieves high precision in detecting skin contact while maintaining reliability by excluding false detections from other materials
2Productivity
If the needle can be moved to the operating position freely, then the injection process is faster and easier, but the risk of accidental needle exposure and breakage increases
Solution Approach 1:
The system performs preliminary detection of skin contact through the capacitive sensor before allowing the needle to be moved to the operating position. This preliminary verification ensures that the needle is only activated when properly positioned on skin, preventing accidental exposure and breakage while maintaining efficient injection delivery
Solution Approach 2:
The capacitive proximity sensor provides real-time feedback on whether skin contact is detected. The control system uses this feedback to enable or disable needle activation, creating a closed-loop safety mechanism that prevents accidental needle exposure while allowing rapid injection when conditions are appropriate
3Measurement precision
If the sensor is highly sensitive to detect any contact, then contact detection is improved, but the device may detect non-skin materials (dry clothes, wood, plastic, metal, ceramic, glass) leading to false positives
Solution Approach 1:
The electrode geometry is specifically designed to create an electric field pattern that interacts differently with skin versus non-skin materials. The localized field configuration at the through hole provides inherent material discrimination capability while maintaining high sensitivity for detecting actual skin contact
Solution Approach 2:
The detection parameters (capacitance thresholds, sensitivity settings, detection algorithms) are calibrated to recognize the electrical characteristics of skin while filtering out signals from non-skin materials. This parameter optimization enables the sensor to maintain high sensitivity for skin detection while achieving versatility in rejecting false materials
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
Enhances user safety by ensuring medication is only injected when the device is correctly placed on human skin, preventing accidental needle exposure and breakage, thereby reducing risks of medication expulsion and user injury.
Implementation Method 1
a capacitive proximity sensor for detecting proximity or contact of human skin to/with said surface
Data Source
AI summary
An injection device for injecting medication to a patient, comprising a surface (5) having a through hole (3) for passage of a needle, is characterised by further comprising a capacitive proximity sensor (12, 13, 30) for detecting proximity or contact of human skin to/with said surface (5).