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June 2022

How to Improve your Surface Tension Technique
This month we set out to help you improve your technique for measuring surface tension using either DROPimage Advanced (with the Surface Tension Tool or a methods-based experiment) or DROPimage Pro (with the Surface Tension Tool only). To get started please click on the video below to watch it.


First, note that in the video, we are using the current version of DROPimage Advanced, v3.22. However, the methods detailed will work on older versions of DROPimage Advanced as well. Note that if you have DROPimage Pro, you can use the Surface Tension Tool but the Experiment Wizard is only available in DROPimage Advanced.

Before we get started with measuring surface tension, we check our calibration. Note that it's not necessary to recalibrate the instrument on a daily basis. However, it's a good idea to check the calibration periodically to ensure that it has not changed since the last calibration. Follow the prompts shown in the video and verify that the deviation between your current calibration check and the saved calibration values is less than 1%. If it's over that threshold, you should recalibrate.

Once you've checked your calibration, you will want to make sure your dispensing system is thoroughly cleaned. If you are using a microsyringe or Manual Syringe assembly, follow the instructions included with that product to thoroughly clean the syringe and the needle prior to loading the test liquid.

If you are using an Automated Dispensing System to dispense, note that the tubing, valve, and syringe should remain hydraulic (that is, primed with water only) while the dispensing tip will hold the test liquid. If you're not sure how this works, check out this useful video.

Once you are ready to begin dispensing, be sure the needle is in the live video image window and focus on the needle as shown in the video. We recommend that you slowly make a pendant drop and note the volume when it releases. Then go back and make a new pendant drop that is approximately 80% of that maximum volume. This will give you the best and most repeatable results. 

Next we use the Surface Tension Tool. Be sure to select the correct phases. Note that the needle is the solid phase. If you are testing a liquid that is not in the list, you can add it using the Phase Editor. You will need to know its density. Make sure you locate the baseline at the three-phase line (where the needle meets the liquid) in order to take a good measurement. In addition to what's shown in the video, make sure you have no reflections on the drop from a window or other light source. Use the shade to block unwanted light if necessary.

Gamma is the surface tension which is in mN/m. Note that 1 mN/m is the same as 1 dyne/cm. Surface tension is a force measurement. We also report the drop area, volume, height and width (in mm).

Next we use the Experiment Wizard to create a methods-based surface tension experiment. This method is ideal for dynamic and time-dependant studies. In the video we use an equidistant time interval of 0.5 seconds with 15 total measurements. Since we're measuring the surface tension of water in an environmentally static condition, not much will change over time as you can see in the results.

If you find our video useful, be sure to like and subscribe to our channel.

DROPimage Advanced
We've been busy making new videos this past month. The video below presents an overview of DROPimage Advanced. Whether you are a potential customer or an existing user of DROPimage, I think you will find this video useful.


First, we walk through the steps of performing a valid calibration. This is essential for all measurements but especially for surface tension. We then show you how to check the calibration, something you should do daily.

Next we show you how to add a new liquid to the phase editor. You will need to know its density. We then use the Surface Tension Tool to measure the surface tension of our test liquid. We then repeat the measurement using a methods-based experiment created using the Experiment Wizard.

We then measure static contact angle using the Contact Angle Tool. To wrap things up, we then measure dynamic contact angle using a methods-based experiment.

If you do a lot of dynamic contact angle, you may also wish to check out this new video in which we measure dynamic contact angle and show both reporting and graphing capabilities. Be sure to like the videos and subscribe to our channel.

Feel free to contact us if you're interested in upgrading an existing ramé-hart instrument to DROPimage Advanced or if you're interested in a new ramé-hart instrument that includes our DROPimage Advanced software.

New Product Annoucement: Inverted PTFE-Lined Needle
For some time, we have offered both a straight needle made from PTFE as well as a straight PTFE-lined needle. PTFE is a desirable material for dispensing since it's omniphobic. And for over 50 years, we've also offered an Inverted Needle. But before now, we've never had an Inverted PTFE-lined Needle. At the request of multiple customers, we now offer a kit, p/n 100-10-13-18-P, which includes a stainless steel inverted needle along with replaceable PTFE lining with a 0.3mm ID. It can be ordered online here. This new product will make interfacial tension, captive bubble, and liquid/liquid studies much easier for many applications.

Carl Clegg
Director of Sales
Phone 973-448-0305
Contact us


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