Large scale waterjet printing for the ultra-fast high definition sensor sorting technology

Normally, an air jet has a large diameter, so it acts not only on the targeted particles, but also on some unwanted particles around, as shown in Fig.1. To improve the recovery grade, compromises have to be made that either to only pick up those particles of the spatial distance with their neighbors large enough, or to simply prepare a loose distributed feed flow, leaving most of the spatial space empty. The former option results in a low recovery rate and the later one dramatically decreases throughput. Besides, the air blow bars or mechanical actuators relying on mechanical response in switching on and off are relatively slow, which limits the temporal resolution of the sorting process. Therefore, to obtain high purity and high throughput at the same time, both the spatial and temporal resolutions need to be significantly improved, and we think the large scale waterjet printing technology is a very good solution.
Water droplets generated by the waterjet printing device have small size of dozens of micron, and have short time interval of the magnitude in microsecond, which guarantee a high resolution at space and time, respectively. With a thin layer of water accurately accumulated on the surface of the selected particles, adhesive force could be used to take the selected particles away from the stream of the feed, while without removing other particles. Based on the principle of the inkjet printing (Kuhn et al., 1979), we designed and built a large scale waterjet printing device that could apply for the ultra-fast high definition sensor sorting technology. The main difference of the waterjet printing compared to the inkjet printing is that waterjet printing has huge amount of the nozzles, normally to that of thousands, to satisfy the large scale industrial application. Efforts are made to make identical nozzles and also to synchronize and coordinate the thousands of water jets.