June 2015

June 15, 2015

Take CHARGE of Static Issues

Most people are taught to think of electricity via the analogy of running water.  The volume of water moved from point A to point B is analogous to voltage while the rate which the water flows is like electrical current.   Multiply the two together and you have power(P=IxE).  

Static electricity is the opposite of current electricity, in that it does not move.  It just builds up between two non-conducting materials (like plastic and rubber) and sits there, waiting to discharge (Google Triboelectric Effect).  If you have ever touched something and got a brief shock, you have likely experienced static build up and provided the path to ground that discharged that potential energy charge.  If you ever touched something and got a prolonged and painful shock, you have probably been electrocuted and may be reading this from the Great Beyond.

Static build-up occurs in environments that are dry.  Water molecules help diminish charge build up.  Insofar as laboratories are concerned, static is generally not an issue due to controlled temperatures and humidity...but they are not immune.   This can be routinely found to be an issue with ill-behaved liquid handlers.   Disposable plastic pipette tips have been known to 'hang up' or not eject from their mandrels  when humidity levels drop.   I have seen tips appear to dance in mid-air, only held to the mandrel by static charges.   This is dramatically visible with lower volume (384) tips as their mass is less to begin with and is exacerbated by the use of rubber o-rings on the dispense head mandrels.   Rubber, plastic and lack of humidity are the perfect recipe for static cling.

So what can be done?  Well, the simple solution is to add humidity to lab.  If the lab's HVAC system is not capable of effecting changes, you could place a humidifier near your liquid handler.  Just be careful as it is a fine line between adding moisture to the air and saturating your robot.  Get a can of Static Guard from your local grocery store.  These sprays add moisture (water and alcohol, with minerals and salts removed) and are very effective (albeit temporarily) when sprayed directly on rubber o-rings.   Another longer lasting and more pragmatic solution would be to place an ionizing fan right on the liquid handler deck, near your tips racks.  These devices add electrical charges to the air (anions, or negative ions) and the fan blows it across your tips which can change the electron imbalance just enough to offset clinging tip issues.

Don't let your labs environment make you retreat from automated assays....wait for it....here it comes...."CHARGE."    That just happened.  BAM.  

Next Blog - Vision Sensors (they can be used for lots of stuff, including pipette tip issues...)