Capacitive Wetness Detection in Absorbent Articles Using a Built-In Pocket
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Solution Overview
Problem
Existing disposable absorbent articles face issues such as sensing lines affecting appearance, vulnerability to external moisture, unreliable electrical connections, misalignment, and ineffective wetness detection due to resistive systems.
Innovation Solution
Sensing lines are placed inside the diaper with a waterproof covering layer and a built-in pocket to protect against moisture, ensuring face-to-face contact with the sensor, and utilizing electrolytic capacitance for accurate wetness detection, leveraging the diaper's elastic force for secure fixation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sensing lines are printed on the outer surface of the backsheet with carbon ink, then wetness detection function is achieved, but the appearance of the diaper is affected and external moisture causes false alarms
Solution Approach 1:
The sensing lines are extracted from the outer surface and relocated to the inner surface of the backsheet, separating the sensing function from the external environment. This extraction eliminates exposure to external moisture while maintaining the wetness detection capability through contact with internal urine.
Solution Approach 2:
The sensing lines are nested within the diaper structure by embedding them in the inner surface of the backsheet, creating a hierarchical arrangement where the sensing function is contained within the protective diaper structure, shielding it from external harmful factors.
2Ease of operation
If sensor is attached to the outside of diaper, then wetness detection is enabled, but the sensor is hard to secure and alignment depends on naked eye causing misalignment
Solution Approach 1:
The sensing lines are pre-positioned and fixed on the inner surface of the backsheet during diaper manufacturing, creating a predetermined accurate reference position. The sensor is then simply attached to the outer surface without requiring precise alignment, as the sensing function is achieved through the pre-established sensing line positions.
Solution Approach 2:
The sensing lines act as an intermediary element between the external sensor and the internal urine, enabling wireless or contactless capacitance-based detection. This intermediary eliminates the need for direct mechanical connection and precise alignment between sensor and sensing lines.
3Object-affected harmful factors
If sensing lines are set inside the diaper, then appearance is improved and protection from external moisture is achieved, but reliable electrical connection with sensor becomes more difficult
Solution Approach 1:
The traditional mechanical contact-based sensing system is replaced with a capacitance-based sensing system. The sensing lines measure urine presence through electrical field interaction and capacitance changes rather than direct physical contact, eliminating the need for reliable electrical connections through tight contacts while maintaining sensing accuracy.
Solution Approach 2:
The sensing mechanism transitions from resistance-based (requiring direct contact) to capacitance-based (measuring electrical field changes). This parameter change allows the sensing lines to detect urine presence through dielectric constant changes in the surrounding medium, enabling reliable detection without direct electrical contact.
4Ease of operation
If pocket is set outside the diaper, then sensor fixation is attempted, but the pocket cannot use waist elasticity and electrical connection reliability is reduced
Solution Approach 1:
The pocket structure is moved from the outer surface to the inner surface of the backsheet, changing its spatial dimension and integration level. This internal positioning allows the pocket to benefit from the diaper's waist elasticity and three-dimensional compression forces, improving both sensor fixation and electrical connection reliability through natural structural forces.
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 enhances reliability and convenience by eliminating aesthetic impact, protecting against moisture, ensuring reliable electrical connections, and enabling accurate wetness detection without misalignment, facilitating mass production and versatility.
Implementation Method 1
the sensing lines can realize the wetness detection function of the absorbent article through the dielectric layer by means of electrolytic capacitance
Implementation Method 2
the sensing lines can realize the wetness detection function of the absorbent article through the dielectric layer by means of electrolytic capacitance
Implementation Method 3
a separable part between the contact surface and the waterproof covering layer constitutes a built-in pocket
Data Source
Figure 1~2B
Figure 3A~3B
Figure 4A~5
AI summary
An intelligent absorbent article (10) based on a capacitive sensing film (40) and a built-in pocket (26), a system device implementing monitoring of a wetness state of the intelligent absorbent article (10), and two types of capacitive sensing film (40) comprising the built-in pocket (26) and suitable for producing the intelligent absorbent article (10). The intelligent absorbent article (10) comprises a disposable absorbent article, a capacitive sensing film (40), a built-in pocket (26), and a short circuit protection mechanism. The disposable absorbent article comprises a surface layer (11), an absorbent layer, and a bottom film (15). The sensing film (40) comprises a contact surface, a sensing surface (62), a dielectric layer, and at least two sensing lines (21,22); the dielectric layer enables the sensing lines (21,22) to be isolated and insulated from the sensing surface (62); and when the sensing surface (62) is wetted by liquid contained in an electrolyte, the sensing lines (21,22) can pass through the dielectric layer and achieve a wetness detection function of the sensing surface (62) in an electrolytic capacitive mode. The built-in pocket (26) is used for inserting a sensor, and the contact surface provides convenience for face-to-face contact and electric connection of the sensor and the sensing liners (21,22). The short-circuit protection mechanism is used for protecting the sensing lines (21,22) from being affected by wetness inside and outside the disposable absorbent article.