Resonant acoustic rheometry (RAR) is a contactless technique for measuring viscoelasticity of soft materials based on the resonant surface waves generated on a sample surface using a dual-mode ultrasound technique. This study reports the development and validation of a portable RAR system for enabling rapid, co-localized, and simultaneous viscoelastic and acoustic characterization of multiple soft material samples. Our results reveal strong correlation of RAR measurements of Young's modulus and viscosity in polyethylene glycol hydrogels with the storage and loss modulus measured using a dynamic mechanical analysis instrument. In addition, RAR measurements of Young's modulus and viscosity exhibited positive correlation with the speed of sound and acoustic attenuation measured during RAR. These results expand the utility of RAR as an integrated tool for acoustic-mechanical characterization of soft viscoelastic materials.

Background/Objectives: The timely evaluation of blood clot formation and breakdown is essential in the care of patients with severe bleeding or critical illness. Resonant acoustic rheometry is a novel, non-contact ultrasound method that measures changes in the viscoelastic properties of blood in a standard microplate format. Here, we present the first clinical description of whole blood coagulation and fibrinolysis assessed with resonant acoustic rheometry, with paired thromboelastography measurements for comparison. Methods: In this retrospective analysis, whole blood samples from three critically ill patients were divided and tested under four different conditions that included a control mixture, kaolin activation, tissue factor activation, and a tissue factor mixture supplemented with tissue plasminogen activator. The resonant acoustic rheometry system obtained real time measurements of resonant surface waves and displacements from the samples. Heat maps and spectrograms of the resonant surface waves were analyzed to determine the onset of clotting, the rate of viscoelastic stiffening, the time to maximum rigidity, and the onset as well as magnitude of fibrinolysis. These measurements were compared with thromboelastography reaction time, clot strength, fibrinogen contribution, and lysis values. Results: Resonant acoustic rheometry detected reproducible transitions from liquid to clot and from clot to lysis in all samples. Activator-dependent changes in clot initiation and propagation matched the expected hierarchy observed in thromboelastography. Significantly, samples exposed to tissue plasminogen activator demonstrated a clear fall in resonant frequency and a corresponding rise in surface displacement that reflected fibrinolysis. The technique also reproduced clinically meaningful patterns of hemostasis that aligned with each patient’s underlying disease. Conclusions: Whole blood clotting can be measured with resonant acoustic rheometry in a manner that aligns with established clinical assays. These results suggest strong potential for future use of resonant acoustic rheometry as a cost-effective, complementary platform for rapid, scalable, and clinically informative hemostatic assessment.