Solid Colorimetric Hydrogel via Gamma-Ray Irradiation

The patent changes the triggering parameter from immediate skin temperature/pH response to a time-dependent refractive index change. The hydrogel composition uses a specific refractive index difference between water and oil phases that only manifests after a predetermined time period, allowing the mask pack to maintain its appearance during application and then visually indicate when to remove it.

The patent employs a disposable mask pack design where the color-changing function is integrated into the single-use hydrogel composition. The refractive index-based indication system provides a one-time visual signal during the brief mask application period, eliminating the need for reusable indicators that would require cleaning and maintenance.

The patent converts the harmful immediate chemical reaction to a beneficial safe physical phenomenon. Instead of using metals or conjugation compounds that can elute and cause skin irritation, the invention uses the natural refractive index properties of water and oil phases in the hydrogel. The visual indication arises from light scattering due to refractive index differences that change over time, a completely safe physical process that eliminates elution risks.

The patent replaces the chemical mechanism (metal-based color change) with an optical-physical mechanism (refractive index difference). The color change function is achieved not through chemical reactions but through optical properties of the hydrogel structure itself, specifically the refractive index contrast between water and oil phases that evolves over time.

The patent creates a composite hydrogel system combining multiple components: hydrophilic polymer, water, oil phase, and surfactant. This composite structure provides both skin penetration capability through the hydrophilic polymer and stability through the balanced composition. The oil phase and surfactant work together to stabilize the hydrogel matrix, preventing water loss while maintaining the desired physical properties.

The patent applies different properties to different components of the hydrogel system. The hydrophilic polymer provides skin penetration and moisture retention, while the oil phase provides structural stability and prevents water loss. The surfactant locally stabilizes the interface between water and oil phases. This division of functional responsibilities among components achieves both skin penetration and physical stability.

The patent extracts and removes the harmful preservative component from the mask pack formulation. By using a single-use disposable design with sterile packaging, the invention eliminates the need for preservatives that would otherwise be required to prevent microbial growth in reusable products. The sterile barrier provided by the packaging system replaces the chemical preservative function.

The patent applies preliminary sterilization through sterile packaging and single-use design before the product reaches the user. The mask pack is sterilized during manufacturing and sealed in sterile packaging, preventing microbial contamination without requiring skin-contact preservatives. This preliminary action eliminates the need for harmful preservatives that would irritate the skin.