Modifications to a transepidermal water loss (TEWL) device

OVERVIEW

• Operates rapidly at higher relative humidity levels, offering faster measurement and easier calibration over prior designs. 
• Real-world applications include skin barrier breakdown evaluation, dermatology, cosmetics, and food allergy monitoring.

BACKGROUND

Transepidermal water loss (TEWL), or insensible sweating, measures water flux emanating from skin to evaluate skin barrier integrity associated with conditions like atopic dermatitis. Common measurement approaches rely on hygrometer-based systems categorized into open and closed chamber designs. Open chamber systems use vertically arranged humidity sensors but remain highly susceptible to ambient airflow fluctuations. Closed chamber systems mitigate ambient interference; however, unvented configurations suffer from internal moisture accumulation that prevents continuous monitoring. Alternative closed models incorporate active cooling condensers to convert vapor into ice, yet these systems are bulky, require high power consumption, cause skin discomfort, and cannot be made wearable. Previous wearable closed-chamber active venting approaches struggled with slow sensor responses when adjusting internal relative humidity levels. Consequently, there is a clear need for an improved device that rapidly, accurately, and reliably matches ambient humidity while maintaining environmental isolation.

INNOVATION

The proposed invention introduces modified closed-chamber TEWL device configurations featuring an active pump and dual-inlet architecture to rapidly achieve desired chamber humidity. Beyond a primary inlet providing dry air through a moisture filter, the system incorporates a secondary inlet to introduce ambient air directly. Airflow pathways are controlled either manually using caps or electronically via a 3-port valve that prevents moisture trapped in filters from entering during ambient air intake. Small-diameter fluidic channels (1 mm or smaller) in elbow, U-shaped, or serpentine geometries create high flow resistance, preventing vapor diffusion loss and isolating the chamber from surrounding environmental turbulence during measurement. The active venting mechanism rapidly resets humidity without depending on sensor feedback delays. Real-world applications encompass dermatology, cosmetic skin monitoring, tracking skin barrier function, and emerging uses such as monitoring allergic reactions and food allergies.

RELATED TECHNOLOGY

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