The most important characteristics of pins, and the primary determinates of the volume of liquid transferred, are the physical features and the speed of withdrawal. The list below summarizes all the factors that contribute to the volume delivered. With each application these factors can be controlled and standardized so that the delivery volumes are very reproducible. With most applications the CV's of pin volume transfers are less than 5%.
1. Pin Diameter. The greater the diameter the larger the hanging drop and the greater the volume transferred. We have developed very precise methods and treatments of the pins to achieve very reproducible volume transfers.
2. Volume of slot in the pin. We use a very exact EDM process to create precision volume slots. The larger the slot the greater the volume transferred.
3. Speed of removal of pin from source liquid. The faster the speed of pin removal from the liquid the greater the volume transferred as the liquid does not have time to drain from the sides of the pin. Increasing the speed of withdrawal from the source plate by 7- fold will increase the volume delivered by as much as 3 fold in a linear relationship. This phenomenon can be exploited to expand the range of delivery volume for a single pin. The chart below illustrates the effects of increasing the speed 7- fold. The speed range is from 0.78 cm/sec to 5.7 cm/sec. Use this chart to select the pin that will deliver in your desired range.
4. Depth to which the pin is submerged in source plate. The greater submersion depth the greater the volume transferred on the sides of the pin.
5. Depth to which the pin is submerged in recipient plate liquid. The greater the depth the greater the volume transferred as long as it is at least equal to the depth of the source well.
6. Microplate well diameter. The larger the well diameter the greater the volume transferred. This has to do with the proximity of the well meniscus affecting the surface tension of liquid in the middle of the well where the pin removes the liquid. See this table comparing 96 and 384 well microplates and the volumes transferred.
7. Surface tension of the pin. The greater the surface tension the smaller the volume transferred. Hydrophobic/lipophobic coatings have the most effect on the larger diameter pins and at the lower speeds of withdrawal.
8. Surface tension of the liquid being transferred. The greater the surface tension the smaller the volume transferred.
9. Speed of pin striking recipient dry plate. The faster the striking speed the greater the volume transferred.
10. Surface tension of the dry plate. The less the surface tension the greater the volume transferred.
Select The Volume You Need To Transfer For Your Application
Delivery Volume Ranges
Delivery volume range is determined by speed of withdrawal from source liquid.
slow speed = 0.78 cm/sec = low volume delivery range
fast speed = 5.70 cm/sec = high volume delivery range
Follow this link to assay methods
The links below are to delivery volume range tables for uncoated and hydrophobic coated delivering either DMSO or Aqueous solutions in liquid to liquid transfers.
DMSO TRANSFERS WITH UNCOATED AND HYDROPHOBIC COATED PINS
AQUEOUS TRANSFERS WITH HYDROPHOBIC COATED PINS
AQUEOUS TRANSFERS WITH UNCOATED STAINLESS STEEL PINS
A Guide for Selecting the Right Pin for Your Application
1. What volume do you need to transfer? DMSO? Aqueous? See these tables to determine your options. Also consider custom slot pins.
2. What volume is in the source plate wells? If it is small a slot pin will have a definite advantage.
3. Will the source plate have wells with significantly different levels of liquid? Cherry picked source plate or edge drying effect?. If yes and if the absolute volume transferred is critical, then select the largest slot pin that is in your transfer range. This will minimize the effect of liquid height on the volume of liquid carried on the sides of the pin. Also consider custom slot pins.
4. Does the material transferred bind non-specifically to stainless steel? If yes then select the Hydrophobic or lipophobic coated pins. If no, select the uncoated pins.