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Forchheimer D.,KTH Royal Institute of Technology | Platz D.,KTH Royal Institute of Technology | Tholen E.A.,Intermodulation Products AB | Haviland D.B.,KTH Royal Institute of Technology
Applied Physics Letters

We demonstrate quantitative force imaging of long-range magnetic forces simultaneously with near-surface van-der-Waals and contact-mechanics forces using intermodulation atomic force microscopy. Magnetic forces at the 200 pN level are separated from near-surface forces at the 30 nN level. Imaging of these forces is performed in both the contact and non-contact regimes of near-surface interactions. © 2013 AIP Publishing LLC. Source

Forchheimer D.,KTH Royal Institute of Technology | Platz D.,KTH Royal Institute of Technology | Tholen E.A.,Intermodulation Products AB | Haviland D.B.,KTH Royal Institute of Technology
Physical Review B - Condensed Matter and Materials Physics

We present a method to reconstruct the nonlinear tip-surface force and extract material properties from a multifrequency atomic force microscopy (AFM) measurement with a high-quality-factor cantilever resonance. In a measurement time of ∼2 ms, we are able to accurately reconstruct the tip-surface force-displacement curve, allowing simultaneous high-resolution imaging of both topography and material properties at typical AFM scan rates. We verify the method using numerical simulations, apply it to experimental data, and use it to image mechanical properties of a polymer blend. We further discuss the limitations of the method and identify suitable operating conditions for AFM experiments. © 2012 American Physical Society. Source

Platz D.,Albanova University Center | Forchheimer D.,Albanova University Center | Tholen E.A.,Intermodulation Products AB | Haviland D.B.,Albanova University Center
Nature Communications

Knowledge of surface forces is the key to understanding a large number of processes in fields ranging from physics to material science and biology. The most common method to study surfaces is dynamic atomic force microscopy (AFM). Dynamic AFM has been enormously successful in imaging surface topography, even to atomic resolution, but the force between the AFM tip and the surface remains unknown during imaging. Here we present a new approach that combines high-accuracy force measurements and high-resolution scanning. The method, called amplitude-dependence force spectroscopy (ADFS), is based on the amplitude dependence of the cantilever's response near resonance and allows for separate determination of both conservative and dissipative tip-surface interactions. We use ADFS to quantitatively study and map the nano-mechanical interaction between the AFM tip and heterogeneous polymer surfaces. ADFS is compatible with commercial atomic force microscopes and we anticipate its widespread use in taking AFM toward quantitative microscopy. © 2013 Macmillan Publishers Limited. All rights reserved. Source

Sanandaji N.,KTH Royal Institute of Technology | Oko A.,Swedish Institute for Surface Chemistry | Haviland D.B.,KTH Royal Institute of Technology | Tholen E.A.,Intermodulation Products AB | And 2 more authors.
European Polymer Journal

Inkjet printing is a technique for the precise deposition of liquid droplets in the pL-volume range in well-defined patterns. Previous studies have shown that inkjet printing is attractive in polymer technology since it permits the controlled deposition of functional polymer surfaces. We suggest that the technique might also be useful for studying crystallization, in particular confined crystallization. Inkjet printing is a non-contact deposition method with minimal risk of contamination, which allows the exact deposition of both polymer solutions and polymer melts. This paper demonstrates the possibility of utilizing the technique to create surfaces where polymer chains form isolated small structures. These structures were confined by both the low polymer content in each droplet and the time constraint on crystal formation that arose as the result of the rapid solvent evaporation from the pL-sized droplets. In theory, inkjet printing enables the exact deposition of systems with as few as a single polymer chain in the average droplet. With appropriate instrumentation, the versatile inkjet technology can be utilized to create whole surfaces covered with polymer structures formed by the crystallization of small, dilute and rapidly evaporating droplets. 110 pL droplets of a 10-6 g L -1 poly(caprolactone) solution in 1-butanol have been deposited and studied by atomic force microscopy. Small structures of ca. 10 nm thickness and ca. 50 nm diameter also seemed to exhibit crystalline features. Some of the small structures had unusual rectangular forms whilst others were interpreted to be early precursors to six-sided single crystals previously observed for poly(caprolactone). The unusual forms observed may have resulted from the entrapment of crystal structures into metastable phases, due to the limited amount of polymer material present and the rapid evaporation of the droplets.© 2012 Elsevier Ltd. All rights reserved. Source

Borysov S.S.,KTH Royal Institute of Technology | Platz D.,KTH Royal Institute of Technology | De Wijn A.S.,University of Stockholm | Forchheimer D.,KTH Royal Institute of Technology | And 4 more authors.
Physical Review B - Condensed Matter and Materials Physics

We propose a theoretical framework for reconstructing tip-surface interactions using the intermodulation technique when more than one eigenmode is required to describe the cantilever motion. Two particular cases of bimodal motion are studied numerically: one bending and one torsional mode, and two bending modes. We demonstrate the possibility of accurate reconstruction of a two-dimensional conservative force field for the former case, while dissipative forces are studied for the latter. © 2013 American Physical Society. Source

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