SILICON NEEDLE ARRAY ON FLEXIBLE SUBSTRATE FOR FLUID TRANSFER

Transdermal delivery is an attractive alternative, but it is limited by the extremely low permeability of skin. To solve this problem, a novel means--micro needle array based on micro electro-mechanical system （MEMS） technology, is provided to increase permeability of human skin with efficiency, safety and painless delivery. The fabrication method consists of a sequence of deep-reactive ion etching （DRIE）, anisotropic wet etching and conformal thin film deposition. The novel technology can enable the realization of micro fabricated micro needle array on a flexible silicon substrate. The micro needle array can be mounted on non-planar surface or even on flexible objects such as a human fingers and arms. The fabricated hollow wall straight micro needles are 200 μm in length, 30 μm inner diameter, and 50 μm outer diameter with 250 μm center-to-center spacing. Flow rate test proves that the polymeric base construction is important to function of micro needles array in package. Glucose solvent tests show that surface tension is the dominant force to affect the characters of flow in micro needles channel.

Thermal degradation and hydrolysis depolymerization of printing ink components for plastic packaging in recycling processes: a review

This review covers the decomposition mechanisms of various printing ink binder resins,with a particular focus on their behavior under extrusion conditions in the mechanical recycling process of polyolefin(PO)based plastic packaging.Thermal degradation and hydrolysis of the nitrocellulose(NC)-the most used binder for flexographic surface printing on single-layer flexible plastic packaging,occur concurrently during the mechanical recycling process under 160-210℃.For other printing ink binders,polyurethane(PU)noticeable degradation takes place between 200 and 300℃,mostly above 250℃.However,with the involvement of humidity,degradation by hydrolysis can start from 150℃.A similar effect is also discovered with the cellulose acetate(CA)derivatives,which are thermally stable until 300℃ and can be hydrolyzed at 100℃.The thermal stability of polyvinyl butyral(PVB)is not influenced by humidity,with thermal stability ranging from 170 to 260℃,depending on different types.Ultraviolet(UV)-cured acrylics are thermaliy stable until 400℃.The hydrolysis degradation can take place at room temperature.Moreover,this review covers the thermal stability of different colorants used for printing ink application and elaborates on several thermal-stable alternatives of some common colors.This study further reviews how the binder resin affects the quality of recyclates,revealing it to be not only induced by the degradation of the binder resin but also by the immiscibility between the plastic and binder resin.In advanced recycling processes,mainly selective dissolution-precipitation and pyrolysis,the presence of binder resin and its degradation products could stll affect the quality of the product.This review accentuates the imperative need for in-depth research to unravel the impact of printing ink constituents on the quality of recycled products.