Chemical Physics Lab
MUSIC-mode AFM

MUSIC-mode Atomic Force Microscopy

Nanoscale depth profiles of soft polymer surfaces

  • Atomic force microscopy image of a polystyrene-functionalized graphene oxide layer (left) and depth profile of the tip-sample interaction (right). Figure: M. Dehnert, E.-C. Spitzner, F. Beckert, C. Friedrich, R. Magerle, Macromolecules 49, 7415–7425 (2016); © 2016 American Chemical Society.
  • Oligothiophene derivatives self-assemble into nanofibrils with a helical core surrounded by a soft shell of polyisoprene ligands. The shape and local nanomechanical properties of the fibrils deposited on a substrate can be imaged using MUSIC-mode atomic force microscopy. Data from: E.-C. Spitzner et al., ACS Macro Lett. 1, 380–383 (2012). Illustration: E.-C. Spitzner, R. Magerle.
  • 3D depth profile of crystalline lamellae below the surface of an elastomeric polypropylene film. Figure: E.-C. Spitzner, C. Riesch, R. Magerle, ACS Nano 5, 315–320 (2011); © 2011 American Chemical Society.

Tapping mode atomic force microscopy is the preferred method for high-resolution imaging of soft surfaces such as soft polymers, fluids, or living cells. In this process, the shape of the surface is scanned line by line with a very fine, vibrating tip that penetrates a few nanometers into the soft surface. This penetration of the tip into the sample was previously considered an undesirable side effect of this measurement method, and the representation of the surface was only possible as a flat area.

Dr. Eike-Christian Spitzner had the idea of using the penetration depth information for an imaging method and to reconstruct depth profiles and volume images of the near-surface area of soft materials, e.g. block copolymers and elastomeric poly propylene [1]. The measurement method works in a similar way to touching the back of a hand: the vibrating tip touches the sample surface like a finger touches the surface of the back of a hand. With a little more pressure, the soft tissue under the skin gives way and the finger can be used to sense stiff and soft spots under the surface. When the finger is withdrawn, the tissue of the back of the hand returns to its original shape. The tip of the atomic force microscope can also penetrate the surface of soft samples to a certain point without causing any permanent deformation.

A variation of this method is the multi-set point intermittent contact (MUSIC) mode [2], which can be used to image soft and fragile nanoscale objects reliably and free of control artefacts using tapping mode atomic force microscopy. Dr. Eike-Christian Spitzner was awarded the Edgard Heinemann Prize 2012 [4] for these two papers [1,2], which are part of his doctoral thesis [3].

Over the past years, we have used these two methods to study a variety of molecular materials, including supramolecular aggregates [4], single collagen fibrils and natural tendons [5-7], polymer-functionalized graphene oxide films [8], and semiconducting polymers [10-12].

[1]  E.-C. Spitzner, C. Riesch, R. Magerle, ACS Nano 5, 315–320 (2011).
[2]  E.-C. Spitzner, C. Riesch, R. Szilluweit, L. Tian, H. Frauenrath, R. Magerle, ACS Macro Letters 1, 380–383 (2012).
[3]  E.-C. Spitzner, Dissertation, TU Chemnitz (2012). PDF
[4]  Uni aktuell from 13.04.2013.
[5]  E.-C. Spitzner, S. Röper, M. Zerson, A. Bernstein, R. Magerle, ACS Nano 9, 5683–5694 (2015).
[6]  M. R. Uhlig, R. Magerle, Nanoscale 9, 1244–1256 (2017).
[7]  R. Magerle, M. Dehnert, D. Voigt, A. Bernstein, Analytical Chemistry 92, 8741–8749 (2020).
[8]  M. Dehnert, E.-C. Spitzner, F. Beckert, C. Friedrich, R. Magerle, Macromolecules 49, 7415–7425 (2016).
[9]  M. Dehnert, R. Magerle, Nanoscale 10, 5695–5707 (2018).
[10]  M. Zerson, E.-C. Spitzner, C. Riesch, R. Lohwasser, M. Thelakkat, R. Magerle, Macromolecules 44, 5874–5877 (2011).
[11]  M. Zerson, M. Neumann, R. Steyrleuthner, D. Neher, R. Magerle, Macromolecules 49, 6549–6557 (2016).
[12]  S. Vazirieh Lenjani, M. Zerson, Q. Wang, M. Sommer, R. Magerle, ACS Macro Letters 8, 1611–1616 (2019).