The cheap and easy solution (depending on your hardware) to avoid charge accumulation for one-way sorting is to push the central waste stream collection off to the side (Dick Stovel taught us to use a chopped-off yellow tip of the right length, wedging it in to push the collector over)--set the voltage balance to push the central stream into the waste collection, and the sort stream to be absolutely vertical (i.e., no net charge). You can aim a drop into a very small area using this method, and for large sorts, there's no charge accumulation. It would be nice if manufacturers would make the necessary accomodations to make "vertical" sorts easier to set up; in my opinion, there's no reason it shouldn't be done anytime you do a one-way sort! mr At 10:35 PM -0500 11/25/02, Howard Shapiro wrote: >Larry Polsky wrote- > >>As a newcomer to sorting, I would appreciate any thoughts or comments on >>the need for inserting a static drain wire into non-conducting >>sort-collection tubes. >> >>There are references in the literature (see below*) that note the >>possibility of sorted droplets being repelled by static charge that can >>accumulate on non-conducting, plastic collection tubes. The suggestion >>made in these references is to insert a grounded drain wire into the >>collection tube to dissipate any charge. However, two experienced sorters >>who I have asked about this have not seen static accumulation to be a >>problem and do not use drain wires. The suggestions have also been made >>to use glass tubes (not always possible) or to coat non-conducting >>collection tubes with serum to achieve the same result. > >The droplets you sort are charged. If you sort them into a nonconductive >vessel, they stay charged (you can pick up a shock by dipping your finger >into a weight boat full of sorted droplets, but it's kind of hard to get a >finger into one of the small tubes typically used for sorting). Once you >accumulate a pool of charged droplets, they tend to repel droplets of like >charge. I don't sort much, but when I have done sorts, I have noted some >strange behavior of droplets, which seemed to go away when I used a >grounding wire. If you are not inexplicably losing cells, you probably >don't need to bother with grounding. If accumulated charge got to be a >problem, the best solution might be to have collection tubes made of >conductive plastic. > >-Howard
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