Stimuli-Responsive Hydrogel Antenna for Battery-Free Diaper Sensing
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Solution Overview
Problem
Existing 'smart-diaper' solutions face challenges such as high cost, large form factor, need for batteries, and safety concerns due to metal components, making them unsuitable for disposable diapers and user comfort.
Innovation Solution
Integration of a conductive stimuli-responsive hydrogel-based non-metal antenna with a UHF RFID tag and wireless data communication IC, which activates upon interaction with an activating agent to transmit power and enable wireless communication, eliminating the need for batteries and metal components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external sensors are fabricated into diapers, then health monitoring capability is improved, but cost increases making them economically infeasible for disposable diapers
Solution Approach 1:
The patent employs a passive RFID tag with hydrogel antenna that can be disposed of with the diaper, eliminating the need for expensive reusable sensor components. The hydrogel antenna is inexpensive to manufacture and integrates directly into the disposable diaper structure, making health monitoring economically feasible for single-use products.
Solution Approach 2:
The patent extracts the battery and active electronics from the sensor system, retaining only the passive RFID tag and hydrogel antenna. This extraction eliminates complex power management requirements and reduces manufacturing complexity, enabling integration into disposable diapers while maintaining health monitoring functionality.
2Ease of operation
If batteries are included for wireless communication, then communication capability is improved, but form factor increases making embedding difficult
Solution Approach 1:
The patent removes the battery from the system entirely by using a passive RFID architecture. The RFID tag harvests energy from the reader's electromagnetic field to power the hydrogel antenna, eliminating the need for bulky battery compartments and enabling thin, flexible integration into diaper layers.
Solution Approach 2:
The patent replaces the mechanical battery-powered system with an electromagnetic energy harvesting system. The passive RFID tag uses electromagnetic induction to receive power wirelessly from the reader, substituting a mechanical power source with a field-based energy transfer mechanism that requires no physical space for battery storage.
3Reliability
If metal components are used in sensors, then conductivity and signal transmission are improved, but safety and comfort are compromised
Solution Approach 1:
The patent changes the material parameter from metal to conductive hydrogel. The hydrogel maintains electrical conductivity necessary for RFID signal transmission while being biocompatible, non-irritating, and safe for prolonged contact with sensitive skin areas, thus resolving the conflict between signal transmission and safety.
Solution Approach 2:
The patent uses a composite hydrogel material that combines electrical conductivity with biocompatibility. The hydrogel can be formulated with conductive particles or polymers to achieve sufficient conductivity for RFID operation while maintaining the soft, flexible, and safe characteristics of hydrogel materials for skin contact applications.
4Measurement precision
If active sensors are used for continuous monitoring, then monitoring accuracy is improved, but energy consumption increases requiring external power sources
Solution Approach 1:
The patent employs periodic interrogation by the RFID reader instead of continuous active sensing. The reader periodically activates the passive RFID tag to take measurements, allowing the sensor to remain dormant between measurements and conserve energy, while still providing accurate periodic health monitoring data.
Solution Approach 2:
The passive RFID tag harvests energy from the reader's electromagnetic field during each interrogation cycle, using that energy to power its own measurement and communication functions. This self-powered operation eliminates the need for external batteries or power sources while maintaining measurement capability during active periods.
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 provides a cost-effective, compact, and safe wireless sensing system for health monitoring, seamlessly integrated into diapers, capable of detecting moisture and pH levels without external power sources, enhancing user comfort and economic feasibility.
Implementation Method 1
a conductive stimuli-responsive hydrogel material configured to be inactive prior to an interaction with an activating agent and active upon the interaction with the activating agent
Implementation Method 2
The antenna is further configured to transmit power to turn on the wireless data communication IC only when the non-metal antenna is active
Data Source
AI summary
An agent activated non-metal antenna for an ultra-high frequency (UHF) wireless sensor having a radio frequency identification (RFID) tag in electronic communication with the non-metal antenna, and a wireless data communication integrated circuit (IC), includes a conductive stimuli-responsive hydrogel material configured to be inactive prior to an interaction with an activating agent and active upon the interaction with the activating agent. The antenna is further configured to transmit power to turn on the wireless data communication IC only when the non-metal antenna is active upon interaction with the activating agent.