Flexible Skin Conductivity Sensor with Uneven Electrode Structure
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Solution Overview
Problem
Conventional sensors for measuring skin conductivity have limited sensitivity due to a small skin-electrode contact area, making it difficult to accurately measure stress levels, especially when worn on body parts with less active sweat glands, leading to discomfort and reduced measurement accuracy.
Innovation Solution
A sensor with a flexible base board and electrodes featuring an uneven structure, such as a Pt-black layer or pillar structures, that increases the electrical contact area with skin via sweat, and through holes for sweat evaporation, allowing for efficient measurement of electrodermal activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional flat electrode is used on a rigid substrate, then the manufacturing process is simple, but the skin-electrode contact area is small leading to limited measurement sensitivity
Solution Approach 1:
The electrode surface is transformed from flat to convex curved surface, increasing the contact area with skin. The convex shape allows better adaptation to skin contours and enhances sweat collection, thereby improving measurement sensitivity without significantly complicating the manufacturing process
Solution Approach 2:
The electrode incorporates a porous structure that increases surface area and enhances capillary action for sweat absorption. The porous material allows sweat to be drawn into the electrode structure through capillary forces, increasing the effective contact area and improving conductivity measurement sensitivity
2Ease of operation
If the electrode is made rigid for stable manufacturing, then manufacturing precision is good, but comfort during wear is reduced
Solution Approach 1:
The electrode is fabricated on a flexible substrate such as a flexible printed circuit board (FPCB), allowing the electrode to conform to skin contours and move with body motion. This flexible construction maintains manufacturing precision through rigid patterning processes while enabling wear comfort through material flexibility
Solution Approach 2:
The convex curved surface of the electrode helps it adapt to skin topology, improving comfort during wear. The curved design allows the electrode to follow skin contours rather than forcing a flat surface against curved anatomy, reducing pressure points and improving wearability
3Measurement precision
If sweat is allowed to accumulate on the electrode surface, then electrical contact area increases, but measurement errors occur due to excessive sweat
Solution Approach 1:
The electrode incorporates vibration elements that generate mechanical vibrations to prevent sweat from accumulating excessively on the electrode surface. The vibrations keep sweat in motion and prevent large pools from forming, which could cause measurement errors, while still maintaining sufficient contact for accurate conductivity measurements
Solution Approach 2:
The electrode design includes features that extract or remove excess sweat from the measurement area. By actively managing sweat removal through structural design or active mechanisms, the system maintains optimal sweat levels for measurement without allowing harmful accumulation that would cause errors
4Measurement precision
If the contact area between electrode and skin is increased, then measurement sensitivity improves, but skin-electrode contact resistance increases
Solution Approach 1:
The porous electrode structure increases surface area for sweat absorption through capillary action, improving sensitivity to electrodermal activity. The porous material's high surface area-to-volume ratio allows better sweat collection while maintaining low contact resistance through the capillary-driven sweat transport mechanism
Solution Approach 2:
The electrode uses composite materials combining conductive materials with porous or convex structural elements. This composite construction achieves both high surface area for sensitive measurement and good electrical conductivity for reliable signal transmission, resolving the contradiction between sensitivity and reliability
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 sensor achieves higher sensitivity by reducing skin-electrode contact resistance and eliminating measurement errors from sweat accumulation, enabling accurate stress level measurement on various body parts without discomfort.
Implementation Method 1
the uneven structure may be configured to have protrusions, with gaps defined between the protrusions, so that the sweat secreted onto the surface of skin permeates between the protrusions by a capillary phenomenon
Implementation Method 2
a plurality of through holes is formed through the base board, the electrode, and the uneven structure in a direction perpendicular to a surface of the base board
Data Source
AI summary
Disclosed is a sensor for measuring skin conductivity and a method of manufacturing the same, wherein the sensor includes: a base board made of a flexible material; an electrode provided on a surface of the base board, and transmitting an electrical signal; and an uneven structure provided on the electrode, and configured to increase an electrical contact area with skin via sweat secreted onto a surface of skin.