Forums
Bruker Media
Community Media
Bruker AFM Probes
SPM Digest
Application Notes
NanoTheater
Website
中文
Brochures & Datasheets
Publications
Probes Catalog
Events
Manuals & Documentation
Presentations
Guide to AFM Modes
News
Journal Club
Webinars & Video
Nanovations
Other
Dear all,
I am wondering if there is a way to record Force Volume maps on a Catalyst system recording Defl. vs ZSensor instead of Defl. vs Zpiezo signals?
While imaging living cells in FV for combined topographic and mechanical analysis, ZSensor turns out to be more accurate than Zpiezo, because height variations are huge (several microns). This happens despite our system is freshly calibrated in both Zsensor and Height, I suppose because calibration considers typically variations in height of the order of a few tens or hundreds nm, not microns.
Keeping the z-close loop on during FV is not an option for us, because it requires ramping very slowly.
Point & Shoot is very limited in the number of curves one can put in a grid (max 20x20, why???).
Eventually, we do not have the PFQM plugin, so we cannot save all curves while PFTapping our cells; in any case, in PFT ramping would be too fast, and viscoelastic effects would show up.
I could not manage to instruct the real-time software (v8.15) to consider the ZSensor signal instead of Zpiezo. Is there a way to do this, according to your experience? Is there a possibility to implement this in future version of the software?
I also would like to ask which channel is actually used by software to build the real time topographic map in FV, whether the ZSensor or the Zpiezo.
Thank for any support and comments.
Best regards,
Alessandro
Alessandro Podestà, PhD Dept. of Physics and CIMAINA, Università degli Studi di Milano via Celoria 16 - 20133 MILANO, Italy E-mail: alessandro.podesta@mi.infn.it Web: http://www.mi.infn.it/~podesta/ Res.ID: http://www.researcherid.com/rid/E-6568-2010 ORCID: https://orcid.org/0000-0002-4169-6679
Dear Alessandro,
As you have noted, we do not currently support plotting against Z sensor in Force Volume. That is because the Z sensor needs to be acquired as a separate data channel and we only support collecting a single data channel in FV (not including calculated channels like modulus and adhesion).
You can get results similar to those available in FV by using Point & Shoot. This allows collection of the Z sensor and you can set it up to collect an array of curves similar to the FV array. The downside is that we do not have a way to make a map of Point & Shoot data (as we do with FV), so you would need to analyze the individual curves and then use some external software to convert the list of results into a map (image). This should be possible in Excel, but MATLAB or Python would probably be better.
--Bede
To capture Deflection Error vs Height (Z) Sensor:
In Ramp Mode, set Channel 2 to 'Height Sensor' on the y-axis and 'Time' on the x-axis. This will allow you to then set the x-axis in Channel 1 to 'Ch 2: Height Sensor' and the y-axis to 'Deflection Error'.
When you swtich to Force Volume, this will give you Deflection vs Z sensor when you capture Channel 1 for your FV curves.
Best,
Andrea
Dear Andrea,
thank you for your help.
I tried to follow your indications but it did not work (I also tried the last software version v8.15r3sr5).
In standard force curve panel I can manage to plot Deflection vs Height Sensor instead of Defl. vs Zpiezo, as you suggest. This is what we do routinely. The problem is that in switching to the FV panel this configuration is lost (notice that I cannot switch directly to FV, but I must pass through Scan mode before).
Once in FV, I do not find any menu or other control allowing to define the x-axis. And this is always set to Zpiezo (I am sure because the length of force curve is always EXACTLY equal to the ramp size value, while this is not the case when Zsensor axis is used).
is iscan initialize different channels putting Height Sensor in ch2 and using it as the independent variable when plotting Deflection as y in ch1
Thank you Bede for clarifying this aspect of FV to me. It would be very useful in the future to have the possibility of selecting between Zpiezo and Height Sensor!
A last question: the topographic map in FV is it built relying on the Height Sensor or on the Zpiezo channel?
I am asking this because I worry that If Zpiezo channel is used to build the topografic map in FV, for tall objects like cells that make the piezo travelling a lot we could expect distortions in the height map.
Regards,
Hi Alessandro,
You are correct, the topographic map in FV is built using the height, not the height sensor and you can expect some distortion for very tall samples.
If you are willing to ramp more slowly, you could use closed loop Z with FV. The CLZ feedback loop will linearize the height so that it matches the height sensor, but there is always some error at the turn-around and the approach and retract curves will be slightly offset. If the CLZ gains are optimized it is possible to reduce this offset, but not to eliminate it.
By the way -- in one of your earlier posts you mention that the number of curves is limited in Point&Shoot. That is only partially true -- You can capture thousands of curves in an array in P&S, but there is a limit on how many can be overlaid offline in Nanoscope Analysis. If you create your own offline analysis code, there is no need for that limitation.