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Hello,
I'm using the nanoscope 8.1 software on the catalyst system and basically, I'm trying to measure cell elasticity by indenting cells with a tipped cantilever. I tried using the single approach option (instead of a single ramp) in ramp mode, with a trigger threshold of 100-150 nm deflection, because I wanted to avoid having to indent a cell twice. However, when I viewed the cells live in brightfield, I could see the cantilever being ramped quickly down until it pushed on the cell and retracted once, before the slower ramp (at approximately the velocity I entered) began. Is this suppose to be how single approach works? I was under the impression that this option allows for only 1 ramp until the trigger threshold is achieved before the cantilever retracts so that sensitive samples do not get poked twice. Another question I have is about control of ramp rate vs velocity. It seems like ramp rate (in Hz) dominates over the ramp velocity that I entered in the expanded menu. Can I change that?
Thanks,
Win Pin
Hello, Win Pin,
It's a bit hard to judge like that what could be your problem, but could it be that your AFM does an Engage process first? Somehow the machine needs to know how far away it is from the surface and it gets this information while engaging. So it might not be possible for you to touch your cells only once I guess. However, you can play around in the Engage settings and give a very low Engage Setpoint, so that the Engage force stays very low. For soft cantilevers, the standard Engage Setpoint is 0.15 V I think, so you could an Engage Setpoint of maybe only 0.5 V or so. Could be however that you suffer false engage then. Maybe it helps.
Dietmar
Single approach is like engage and ramp, single ramp is ramp only, so I guess your impression was reversed. The ramp rate and approach velocity is correlated, based on your ramp size setting, you change one, the other changes spontaneously.
Ang Li