If you have recently started using a piezo or STM scanner in your laboratory to look at the molecular structure, topography, and the thermal conductivity of small sample materials, then you undoubtedly want all of your testing to be completed without contamination. Contamination can occur quite easily, especially when sample sizes are so tiny. Keep reading to learn about some easy ways to keep contamination to a minimum so you do not have to complete tests over and over again when you first start using the scanner machine.
Change The Tip Every Time
Since sample materials are scanned and projected onto a screen at their molecular level, even the smallest bit of dust or debris can contaminate one or several of your tests. One of the more common contamination areas that can reduce the accuracy of your results is the scanning tip. This tip is the small wire that is inserted into the end of the piezo scanner tube. Electrical current is passed through the wire and into your sample, and the reaction of the sample to the current will produce your results.
A new tip must be placed within the end of the piezo scanner tube every time you use the machine, and the tip is formed with a piece of platinum iridium wire. This wire is sometimes sold as piezoelectric wire, so make sure to purchase a large spool so you have more than enough.
To reduce contamination concerns, never touch the wire as you prepare a tip. You should instead use needle-nose or flat-nose pliers and wire cutters to work with the wire. Put some vinyl gloves on your hands first, and then clean your tools thoroughly with rubbing alcohol or pure ethanol alcohol. Allow the alcohol to evaporate and then hold the end of the wire in your pliers. Measure a short length of wire. Most piezo tips need to be less than one-half or one-quarter of an inch long. Look in the manual for the scanner to find the exact tip length.
Use your wire cutter to cut the wire. Afterwards, angle your cutters at a 45 degree angle to the end of the wire and snip off the end. This will create the sharp tip. Immediately grasp the wire with a pair of tweezers that have been swabbed with alcohol and secure the wire into the tip end of the piezo tube. Once you have finished your testing, use tweezers to remove the tip without touching the scanner tube with your hand.
Clean The Sample Holder
The piezo scanner will have a sample holder where you can place your sample just underneath the wire tip that extends out from the tube. The holder will have a magnet end that will help to hold your metallic samples. This magnet surface will hold onto metal materials strong enough that an electrical charge can pass through without moving or disturbing the sample material. This means that small particles may be left behind on the magnet sample area once the testing is over.
Since different types of metals will produce widely different results during the scanning process, particulate matter on your sample holder can contaminate your results. You will need to clean the holder, making sure that dust and lint are not left behind in the process. You can use alcohol to clean the holder, and you should wipe it clean when you are done to remove debris. Purchase some lint-free wipes made for either laboratory or clean room facilities to wipe the holder.
Use tweezers to place your sample on the magnetic end of the holder, and use your gloved hands to secure the holder in the scan head.