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Closed-loop Atomic Force Microscopy-Infrared Spectroscopic Imaging Applications for Nanoscale Characterization

By 11th September 2020No Comments

The following study was conducted by Scientists from Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana Champaign, Urbana, IL, USA; Department of Mechanical Engineering, University of Illinois at Urbana Champaign, Urbana, IL, USA; Cancer Center at Illinois and the Departments Chemical and Biomolecular Engineering, Bioengineering, Electrical and Computer Engineering, and Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, USA. Study is published in Nature Communications Journal as detailed below

Nature Communications; Volume 11, Article Number: 3225; (2020)

Closed-Loop Atomic Force Microscopy-Infrared Spectroscopic Imaging for Nanoscale Molecular Characterization


Atomic force microscopy-infrared (AFM-IR) spectroscopic imaging offers non-perturbative, molecular contrast for nanoscale characterization. The need to mitigate measurement artifacts and enhance sensitivity, however, requires narrowly-defined and strict sample preparation protocols. This limits reliable and facile characterization; for example, when using common substrates such as Silicon or glass. Here, we demonstrate a closed-loop (CL) piezo controller design for responsivity-corrected AFM-IR imaging. Instead of the usual mode of recording cantilever deflection driven by sample expansion, the principle of our approach is to maintain a zero amplitude harmonic cantilever deflection by CL control of a subsample piezo. We show that the piezo voltage used to maintain a null deflection provides a reliable measure of the local IR absorption with significantly reduced noise. A complete analytical description of the CL operation and characterization of the controller for achieving robust performance are presented. Accurate measurement of IR absorption of nanothin PMMA films on glass and Silicon validates the robust capability of CL AFM-IR in routine mapping of nanoscale molecular information.


Nature Communications



Kenkel, S., S. Mittal, et al. (2020). “Closed-loop atomic force microscopy-infrared spectroscopic imaging for nanoscale molecular characterization.” Nature Communications 11(1): 3225.