Capacitive Skin Detection in Injection Devices to Prevent Misfire
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Solution Overview
Problem
Existing injection devices lack adequate security measures to prevent accidental medication expulsion and user injury, particularly when placed on hard surfaces or when handling the device, as they do not reliably distinguish between human skin and other materials.
Innovation Solution
Incorporating a capacitive proximity sensor that detects human skin contact while ignoring non-naked body areas and hard surfaces, coupled with a control unit that only allows needle deployment when proper skin contact is confirmed, ensuring safe and accurate injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a proximity sensor is added to detect skin contact, then safety against accidental injection is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical safety switches or pressure sensors with a capacitive proximity sensor that uses electrical capacitance changes to detect skin contact. This substitution reduces mechanical complexity while maintaining safety functionality, as capacitive sensors have no moving parts and can be integrated into the device housing.
Solution Approach 2:
The capacitive sensor acts as an intermediary between the physical act of placing the device on skin and the electronic control system. It translates the physiological property of skin (capacitance) into an electrical signal that the control unit can process, enabling safe injection without direct mechanical contact detection.
2Measurement precision
If the sensor is made highly sensitive to detect all contacts, then detection accuracy improves, but false detection of non-skin materials increases
Solution Approach 1:
The patent changes the detection parameter from simple proximity detection to capacitive coupling detection. Skin tissue has unique dielectric properties (capacitance value around 4-10 pF) that differ from other materials. By measuring capacitance rather than just proximity, the system achieves high detection accuracy while rejecting false positives from non-skin materials through appropriate threshold setting.
Solution Approach 2:
The capacitive sensor is positioned and configured to detect local skin properties at the injection site. The sensor geometry and electrode arrangement are optimized to create an electric field that penetrates through the device housing and interacts specifically with skin tissue characteristics, enabling localized detection with high precision.
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 solution significantly reduces the risk of accidental medication expulsion and user injury by ensuring the needle is only deployed when the device is correctly positioned on human skin, preventing accidental piercing and needle breakage.
Implementation Method 1
a capacitive proximity sensor for detecting proximity or contact of human skin to/with said surface
Data Source
Figure 1~2
Figure 3~4
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 and a capacitive proximity sensor (12, 13, 30) for detecting proximity or contact of human skin to/with said surface (5), is characterised in that said capacitive proximity sensor (12, 13, 30) is so set that a mere contact of a finger on said surface (5) is not detected, and/or is so set to substantially not detect dry clothes, and/or is so set to substantially not detect any of the following materials: dry cotton, dry leather, and/or is so set to substantially not detect any of the following materials: wood, plastic, metal, ceramic, glass.