[3dem] Vitrobot tweezers

[Frederik Peter (ELMI)]

Dear Joseph,

Damaged Vitrobot tweezers are not rare. As Wim Hagen pointed out already, Dumont tweezers (sold under the same number) have a variation in length AND thickness of the tips. When the first Vitrobots were produced this was already noticed. To make vitrification reproducible the size and shape of the tweezers was rigorously standardized. This included length (slightly shorter than average), tips (additional thinning) and rotational symmetry. We noticed that some tweezers had slightly thicker tips which worked as spacers in the blotting process; filter paper was blotting tweezers and not the grid. This was prevented by sparking the tips and thus removing material without deformation of the tips. The screw hole in the tweezers to screw-mount it in the brass dovetail block was also produced by sparking. 
Rotational symmetry implies that all tweezers having the same length, also have the same position between the blot pads. This not only hold for all right-hand workers, but also for left handers using a mirror procedure. Rotational symmetry can be checked in a lathe, in addition we had a small tool in the lab to check length and rotational symmetry.
If you consider all these processing steps it adds up to the costs of an item that looks a simple piece of machining. The commercial price of the golden FEI tweezers has been annoying to a lot of customers. An alternative source (a reputed company in the USA) has made a quotation that could result in a reasonable price for additional/replacement Vitrobot tweezers.
As inventor of the Vitrobot I had an ample supply of excellent tweezers. These were made next door in the engineering/machining department where my co-inventors of the Vitrobot were working. In more than 10 years they  designed and build all prototypes (more than 4 generations) which were tested and improved in my lab. In the lab I noticed that Vitrobot tweezers became the favourite handling tool for EM-grids, a general and reliable precision tool. The use of these tweezers for non vitrification purposes also shortened there effective life-time.

Kind regards,
Peter Frederik
Maastricht     
________________________________________
Van: 3dem-bounces at ncmir.ucsd.edu [3dem-bounces at ncmir.ucsd.edu] namens John Rubinstein [john.rubinstein at utoronto.ca]
Verzonden: donderdag 5 februari 2015 0:08
Aan: 3dem at ncmir.ucsd.edu
Onderwerp: Re: [3dem] Vitrobot tweezers

Dear Joe‎,

We have also done this.
I recommend that after manufacturing a new pair of tweezers with a Vitrobot attachment block you apply Loctite (red)‎/Threadlocker (red) to the screw that secures the tweezers to the block. A screw coming loose with a pair of Vitrobot tweezers could be very dangerous.

Loctite can be purchased at a hardware store. The old Loctite securing the Vitrobot tweezer screw can be removed by heating.

Best regards,
John

Sent from my BlackBerry 10 smartphone.
From: Diaz-Avalos PhD, Ruben
Sent: Wednesday, February 4, 2015 5:14 PM
To: 3dem at ncmir.ucsd.edu
Subject: Re: [3dem] Vitrobot tweezers


Hi Joe,

As Bob pointed out, the easiest thing to do, is to remove the old tweezers and replace them with a new set (they are dumont style L5 tweezers, and you can find them in EMS, part number 0508-L5-PS). You will have to mill them to fit the brass piece and make a hole, which is a tad difficult because they are made of kriptonite or some similar material. Of course, it is critical to place the hole at the proper location. If you want to have some more of the brass pieces made, it is a tad more expensive, but it can be done in any machine shop that has EDM (any decent Engineering Department has one). The brass piece should cost you something in the order of $120 and the tweezers another $50, so in total you should be able to have them made for something ~$200.

Cheers!

Ruben.


On Feb 3, 2015, at 6:59 PM, Joseph Wang <joewang at ucdavis.edu<mailto:joewang at ucdavis.edu>> wrote:

Dear all,

I am thinking to make the customized tweezers for Vitrobot Mk III as the commercial ones are over my budget. Does anyone have a blueprint that can be kindly shared with?

Thank you and best regards,
Joseph
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