While polymer microneedles may easily be fabricated by casting a solution in a mold, either centrifugation or vacuumizing is needed to pull the viscous polymer solution into the microholes of the mold. We report a novel process to fabricate polymer microneedles with a one-sided vacuum using a ceramic mold that is breathable but water impermeable. A polymer solution containing polyvinyl alcohol and polysaccharide was cast in a ceramic mold and then pulled into the microholes by a vacuum applied to the opposite side of the mold. After cross-linking and solidification through freeze-thawing, the microneedle patch was detached from the mold and transferred with a specially designed instrument for the drying process, during which the patch shrank evenly to form an array of regular and uniform needles without deformation. Moreover, the shrinkage of the patches helped to reduce the needles' size to ease microfabrication of the male mold. The dried microneedle patches were finally punched to the desired sizes to achieve various properties, including sufficient strength to penetrate skin, microneedles-absorbed water-swelling ratios, and drug-release kinetics. The results showed that the microneedles were strong enough to penetrate pigskin and that their performance was satisfactory in terms of swelling and drug release.

Abrasive waterjet (AWJ) machining is a new non-conventional machining technology. Compared with other conventional and non-conventional machining technologies, AWJ offers the following advantages: no thermal distortion, small machining force, high machining versatility, etc. Therefore this technology is regarded as a high potential technology in the field of machining difficult-to-cut materials. In this paper, a comprehensive review of research situation about the cutting performance, the cutting mechanism and the measures to improve the cutting quality is given. The application of abrasive waterjet machining in turning, milling and drilling is reviewed finally.

As a unique machining way, Abrasive Waterjet Machining (AWJ) is one of the fastest developing new non-traditional machining methods and has a wide range of machinable materials. In this paper, the machining mechanism in AWJ is theoretically analyzed by impact dynamic mechanics method. There is stagnancy layer between waterjet and workpiece surface. It is found that the stagnancy layer and low energy abrasive particle are the main factors, which weaken machining capability and effective utilizing ratio of energy of AWJ machining. Ultrasonic Vibration Abrasive Waterjet Machining, a new machining method, is put forward and the influence of ultrasonic vibration on machining mechanism of AWJ machining is discussed.

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The effect of cutting parameters such as water pressure, nozzle traverse speed and standoff distance on the granite cutting performance as characterized by kerf width, kerf taper, and striation drag angle are researched with a series of experiments using garnetabrasive and ultra high pressure abrasive water jet numerical control machine tool. The relationship between system pressure and abrasive mass flow rate is also studied. The research results show that the abrasive mass flow rate is only proportional to water pressure and the effect of other cutting parameters is not significant. It is found that an increase in water pressure is associated with an increased kerf width and a decreased kerf taper. The kerf width decreases with the enhancement of nozzle traverse speed, and resulting in a significant increase in kerf taper as the nozzle traverse speed increases. The kerf width increases with the enhancement of standoff distance, and hence it causes a significant increase in kerf taper at the standoff distance domain from 3mm to 4mm and then a little decrease in kerf taper at the standoff distance increasing from 4mm to 5mm. The striation drag angle decreases with an increase in water pressure and a decrease in nozzle traverse speed.