AUTHOR: Igor Sokolov, Tufts University, Boston, USA 

WHEN: October, 9 - 11.30AM

WHERE: Sala de Seminarios, ICMM-CSIC

ABSTRACT: Atomic force microscopy (AFM) provides unique capabilities for studying mechanical properties of materials at the nanoscale. However, conventional AFM measurements are predominantly relative rather than absolute due to deviations from the classical contact mechanics models. It makes inter-laboratory and inter-technique comparisons challenging. The pursuit of absolute (true) moduli represents a critical unmet need in nanomechanical characterization.

     Here I will describe advanced models and techniques enabling absolute measurements of both (quasi) static, the Young’s modulus, and dynamic (storage and loss) moduli. The brush model is introduced to account for surface roughness effects, whether from sample preparation artifacts or intrinsic material features such as biological cell surfaces. I will focus on the robustness of the brush model (weak dependence of the derived results on the model uncertainty). Additionally, the Fourier Transform-nanoDMA (FT-nanoDMA) technique is presented, which simultaneously measures storage and loss moduli across multiple frequencies while testing the linearity of stress-strain response during measurement.

     These methodologies address fundamental limitations in contact mechanics assumptions and provide pathways toward quantitative, reproducible nanomechanical measurements with absolute accuracy. The approaches are validated through systematic comparisons with established nanoindentation benchmarks, demonstrating excellent agreement for absolute modulus values.

SHORT BIO: Igor Sokolov is Professor and Bernard M. Gordon Senior Faculty Fellow at Tufts University, where he explores the frontiers of nanotechnology, imaging, and health. Trained as a physicist in St. Petersburg and earning his Ph.D. at the Russian “NIST,” Sokolov went on to lead nanoengineering and biotechnology labs in Canada and the U.S. before joining Tufts. He has authored over 190 publications, holds 22 patents, and has spent three decades advancing AFM, nanomaterials, self-assembly, and machine learning long before they were buzzwords. His innovations, ranging from new AFM modalities and ultrabright nanosensors to novel diagnostic platforms, span from fundamental physics to practical biomedical tools. Backed by NSF, NIH, the military, and industry, Igor continues to push the nanoscale as both a place of discovery and a source of transformative technologies and fun.