The current study develops a new process for the fabrication of Pt resistor temperature detectors (RTDs), cantilevers covered with a water-absorbent polyimide layer for humidity measurement and the bending-up of cantilevers to determine the flow rate. Pt RTDs are fabricated on the silicon substrate. The temperature measurement is based on the linear resistance variations when temperature changes. The polyimide layer is spun on the cantilever to form a humidity sensing layer. A variation in humidity causes moisture-dependent bending of the micro-cantilever, which changes the measured resistance of the resistor on the microcantilever. The same type of micro-cantilever, without spinning on polyimide, is used to form an anemometer. It is found that the cantilever bends slightly upward as a result of the released residual stress induced in the beam during the fabrication. When wind passes over the cantilever beam, a small deformation occurs. Variations in the flow rate can therefore be determined by measuring the changes in resistance caused by the beam deflection, using a LCR meter.

Candlelight-style, blue hazard-free light sources have been long desired in order to minimize the threats of blue emission on human health, artifacts, ecosystems, and night skies. Flexible light sources can enable numerous innovative products that are wearable, rollable, foldable, and portable. If also transparent, more applications including smart displays, lighting, signage, etc., can be implemented. However, current flexible lighting sources have issues like the use of environmentally unfriendly materials and poor lifetimes. Here, we show the fabrication and lifetime study of a candlelight-style organic light-emitting diode (LED) on high-flexibility, transparent mica that is 100% plastic-free. We found that the mica substrate coated with a transparent conductor survived a record-high bending curvature, i.e., 1/5 mm–1 and 50,000 bending cycles at a 7.5 mm bending radius. The candlelight organic LED fabricated thereon showed a good lifetime that is 83% of that on glass. The blue light-less emission permits at 100 lx an exposure limit of 47,000 s, while the exposure limit is 320 s for a cold-white counterpart; upon exposure at night for 1.5 h, it suppresses 1.6% melatonin, while 30% melatonin is suppressed for the cold-white counterpart. Our results demonstrate how blue hazard-free lighting sources are fabricated on eco-friendly mica that is highly flexible, and the resultant device showed a lifetime approaching that on glass due to its high resistance against moisture and oxygen penetration. The findings suggest that mica can be a good candidate for flexible transparent devices. We expect that these could bring up opportunities to promote omnifriendly lighting applications with a higher degree of design flexibility.

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