[Spm] baseline slope in force curves

[Igor Sokolov]

Dear Olivier,
Thank you for clarification!
I feel that I misunderstood your definition of the "baseline". It seems that
you use this term for the linear complience region (that is usally used to
define the senistivity of photodetector when ramping a rigid surface). I
used before term baseline for the supposed-to-be-constant deflection curve
before the contact. A lot of times that line is not a constant, and some
time even not a straight line at all. This can be due to the interference of
laser reflected from both surface and cantilever, or due to a physical
reason, or (the worse case) both those reasons.
Best regards,
Igor
 
_____________________________________
Igor Sokolov, Ph.D.
Director of Nano-Bio Laboratory (NABLAB), Clarkson University,
Professor,
Department of Physics, 
Department of Chemical and Biomolecular Science,
Clarkson University,
NY Center for Advanced Materials Processing,
Potsdam, NY 13699-5820, USA

office:        315-268-2375
fax:            315-268-6610
E-mail:       isokolov at clarkson.edu <blocked::mailto:isokolov at clarkson.edu> 
Web:          <blocked::http://www.clarkson.edu/~isokolov/>
http://www.clarkson.edu/~isokolov/
______________________________________
 

  _____  

From: Olivier Arnould [mailto:Olivier.Arnould at univ-montp2.fr] 
Sent: Wednesday, October 08, 2008 5:14 AM
To: Igor Sokolov; spm at spmlist.di.com
Cc: schille at uni-muenster.de
Subject: Re: [Spm] baseline slope in force curves


Hi,
 
Thank you for the article. I've never recommanded to remove the baseline
"blindly" too but by using the baseline obtain on silicon substrate for
example (i.e., a stiff sample). This is only for removing the part of the
Z-displacement due to the cantilever deflection and you have to do it
anyway. If an other effect due to an other interaction with your sample
occurs, it will remain even with this (necessary) correction !
 
Best regards,
 
Olivier Arnould
---------------------------------------------------------------------
LMGC 
UMR 5508/University Montpellier 2
Wood and Tree Mechanics Team
cc 048 - Place Eugène Bataillon
F-34095 Montpellier Cedex 05
France
Tél.: +33 (0)4 67 14 96 50
Fax.: +33 (0)4 67 14 47 92
Email: arnould at lmgc.univ-montp2.fr 

----- Original Message ----- 
From: Igor  <mailto:isokolov at clarkson.edu> Sokolov 
To: 'Olivier Arnould' <mailto:arnould at lmgc.univ-montp2.fr>  ;
spm at spmlist.di.com 
Cc: schille at uni-muenster.de 
Sent: Tuesday, October 07, 2008 6:47 PM
Subject: RE: [Spm] baseline slope in force curves

Hi there,
It seems I missed the original question. However, the question was clear,
and important. 
I would not recommend just subtract the base line blindly. We saw a similar
phenomenon on epithelial cells, and initially thought that it was artifact.
But when we got a scanner with larger Z-range, we found that was a real
signal from cell microvilli etc. (cell brush). As a result we developed a
bit more complicated model. This is described in a paper: 
Igor Sokolov, Swaminathan Iyer, Venkatesh Subba-Rao, Ravi M. Gaikwad, and
Craig D. Woodworth, “Atomic Force Microscopy Detects Surface Brush on Cells
In-Vitro”, Applied Physics Letters, 91, 023902 _2007.
Best regards,
Igor
 
_____________________________________
Igor Sokolov, Ph.D.
Director of Nano-Bio Laboratory (NABLAB), Clarkson University,
Professor,
Department of Physics, 
Department of Chemical and Biomolecular Science,
Clarkson University,
NY Center for Advanced Materials Processing,
Potsdam, NY 13699-5820, USA

office:        315-268-2375
fax:            315-268-6610
E-mail:       isokolov at clarkson.edu <blocked::mailto:isokolov at clarkson.edu> 
Web:          <blocked::http://www.clarkson.edu/~isokolov/>
http://www.clarkson.edu/~isokolov/
______________________________________
 

  _____  

From: Olivier Arnould [mailto:arnould at lmgc.univ-montp2.fr] 
Sent: Thursday, September 18, 2008 8:16 AM
To: spm at spmlist.di.com
Cc: schille at uni-muenster.de
Subject: [Spm] baseline slope in force curves


Hi,
 
If I have well understood, I think that this baseline slope is due to the
cantilever deflection that must be substract to the z-displacement to obtain
the indentation depth. This is usually done by doing a force-distance curve
on a stiff material that will give you the baseline slope due to the
cantilever deflection only, i.e., only a negligible indentation occurs so
z-displacement ~ cantilever deflection. You have then to substract this
displacement to the one you obtain on your cell.
 
Best regards,
 
Olivier Arnould
 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://spmlist.di.com/pipermail/spm/attachments/20081008/ede4d0a6/attachment-0002.html