silicon and acetylcellulose

The market for wearable devices such as smart watches and smart glasses continues to grow rapidly. Smart glasses are attracting particular attention because they offer convenient features such as hands-free augmented reality (AR). Since smart glasses directly touch the face and head, the device with high temperature has a detrimental effect on human physical health. This paper presents a thermal network model in a steady state condition and thermal countermeasure methods for thermal management of future smart glasses. It is accomplished by disassembling the state by wearing smart glasses into some parts, creating the equivalent thermal resistance circuit for each part, approximating heat-generating components such as integrated circuits (ICs) to simple physical structures, setting power consumption to the heat sources, and providing heat transfer coefficients of natural convection in air. The average temperature difference between the thermal network model and a commercial thermal solver is 0.9 °C when the maximum temperature is 62 °C. Results of an experiment using the model show that the temperature of the part near the ear that directly touches the skin can be reduced by 51.4% by distributing heat sources into both sides, 11.1% by placing higher heat-generating components farther from the ear, and 65.3% in comparison with all high conductivity materials by using a combination of low thermal conductivity materials for temples and temple tips and high conductivity materials for rims.

Topics: Cellulose; Convection; Lenses; Liquid Crystals; Models, Theoretical; Silicon; Smart Glasses; Temperature

Permeation of caffeine through human skin and artificial membranes (mounted in modified Franz type diffusion cells) was evaluated, either from saturated solutions or from commercially available topical formulations (all containing 3% caffeine). Data interpretation of the caffeine diffusion through human skin does not implicate transfer through pores despite caffeine being a relatively polar molecule. No correlation was found between transfer though the synthetic membranes (cellulose acetate impregnated with isopropyl myristate and silicone rubber soaked in isopropyl myristate) and that observed through skin. The synthetic membranes can be used for assessing product performance in quality assurance but will give little indication of its performance in vivo. The study investigated the percutaneous permeation of caffeine through human skin in order to obtain a mechanistic interpretation of its route of permeation. Synthetic membranes were also examined to determine if they could be used as models for human skin. Different commercial formulations investigated to determine the significance of enhancement strategies.

Topics: Administration, Topical; Caffeine; Cellulose; Central Nervous System Stimulants; Chemistry, Pharmaceutical; Diffusion; Humans; In Vitro Techniques; Kinetics; Membranes, Artificial; Permeability; Silicon; Skin; Skin Absorption; Solubility; Solutions