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Publication Number
US-9283365-B2
Publication Date
2016-03-15
Expiration Date
Abstract
A method of producing projections on a patch including providing a mask on a substrate and etching the substrate using an etchant and a passivant to thereby control the etching process and form the projections, wherein the passivant does not include oxygen.
Core Innovation
The invention relates to producing projections on a patch by providing a mask on a substrate and etching the substrate using an etchant and a passivant to thereby control the etching process and form the projections. The etching process is continuously controlled using the etchant and the passivant. The passivant does not include oxygen, so oxygen-free passivation is used during the etching.
The oxygen-free passivation avoids formation of a silicon oxyfluoride layer and enables controllable projection profiles, including concave, flat, convex, and stepped projection geometry. This control is described as reducing the bullseye effect, reducing the need for hard metal masks, and improving projection robustness for skin penetration. The method is applied to silicon projection needle patches using plasma etching with a passivant that is oxygen-free.
The described approach includes post-etch sharpening based on forming a thermal silicon dioxide layer and then removing silicon dioxide using hydrofluoric acid. The document also describes optional coating, including gold coating and an adhesion layer. The resulting projections are evaluated with penetration into the stratum corneum and analyses including cryo-SEM and confocal multi-photon microscopy to link stepped projection geometry to controlled penetration depth.
Claims Coverage
The independent claim family coverage centers on a method of producing projections on a patch by masking and etching with continuous control using an oxygen-free passivant, resulting in formation of projections with controlled etching profiles. The independent claim contains 1 main inventive focus: oxygen-free passivant used with continuous etchant/passivant control during projection-forming etching.
Mask-defined projection forming using continuously controlled etching with an oxygen-free passivant
A method of producing projections on a patch including providing a mask on a substrate and etching the substrate using an etchant and a passivant to thereby control the etching process and form the projections, wherein the etching process is continuously controlled using the etchant and the passivant, and wherein the passivant does not include oxygen.
Overall claim coverage is directed to controlling projection formation on a patch by continuously controlling etching using an etchant and an oxygen-free passivant, with additional refinements described in dependent claims for mask selection, passivant selection, etchant definition, control strategies, numeric etchant-to-passivant ratios, projection geometry constraints, and optional sharpening/coating steps.
Stated Advantages
Avoids formation of a silicon oxyfluoride layer.
Enables controllable projection profiles, including stepped projection geometry.
Reduces the bullseye effect.
Reduces the need for hard metal masks.
Improves projection robustness for skin penetration.
Documented Applications
Evaluating penetration through skin, including penetration through the stratum corneum and into viable epidermis, using coated silicon projections and needle patch geometries with cryo-SEM and confocal multi-photon microscopy analyses.
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