AFM-nDMA introduces quantitative nanoscale viscoelastic characterization of polymers, probing materials at rheologically relevant frequencies, in the linear regime.
Bulk viscoelastic characterization of polymers is traditionally performed with dynamic mechanical analysis (DMA), operating at small strains to ensure a linear material response, at frequencies from below 1Hz to the low kHz range. In contrast, traditional AFM methods for viscoelastic characterization employ resonant methods that operate at much higher frequencies, and where Tapping Mode based methods are used, the tip-surface contact is made and broken at every cycle, a highly nonlinear process.
Bruker’s AFM-nDMA employs proprietary dual channel detection, phase drift correction, and reference frequency tracking, enabling a small strain measurement in the rheologically relevant 0.1Hz to 20kHz range, at the spatial resolution only AFM can provide. The measurement is embedded in a force curve, enabling contact radius quantification and oscillation in contact, combined with avoidance of lateral forces to enable resolution and reproducibility. The result are nanoscale measurements of storage modulus, loss modulus, and loss tangent that tie directly to bulk DMA, including construction of master curves, extraction of glass transition temperatures, and analysis for the activation energy using Arrhenius law. For the first time, AFM provides complete and quantitative viscoelastic analysis at the nanoscale.
