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Accurately measuring the viscoelastic properties of biomaterials is critical for understanding their functions in biological systems and optimizing their development for specific applications. Conventional methods often require direct physical contact, which hinders longitudinal studies of sterile samples and impose strict requirements in sample preparation. Here, we introduce tensile acoustic rheometry (TAR), a technique for rapid, contactless characterization of soft viscoelastic biomaterials. TAR uses a dual-mode ultrasound approach to apply an upward force impulse, generating oscillatory tensile and compressive motion in a small, free-standing sample (~30 mm3) with its bottom immobilized on a pre-wetted flat surface by capillary stiction. High frequency ultrasound pulse echo detection is employed to track this motion via the movement of the top surface of the sample in real time. In this study, we developed a theoretical framework of the tensile-compression motion of the sample from which Young’s modulus and viscosity of the sample are determined based on the TAR measurements. TAR was validated across a variety of samples, including engineered hydrogels and commercially available natural food products. Results from TAR measurements aligned closely with theoretical predictions, reported values, and shear wave elastography measurements. These findings underscore the versatility and flexibility of TAR as a robust, versatile rheological method for biomaterial characterization with minimal sample preparation requirements. 

Animals are faced with a variety of dangers or threats, which are increasing in frequency with ongoing environmental change. While our understanding of fearfulness of such dangers is growing in the context of predation and parasitism risk, the extent to which non-trophic, interspecific dangers elicit fear in animals remains less appreciated. We provide an experimental test for fear responses of savannah ungulates to a dominant and aggressive megaherbivore, the African bush elephant (Loxodonta africana), and contrast responses to an apex predator known to elicit fear in this system. Using an automated behavioural response system, we contrast vigilance and run responses of ungulates to elephant, leopard (Panthera pardus), and control (red-chested cuckooCuculus solitarius) vocalizations. Overall, we find that ungulates responded to elephant calls, both in terms of an increase in run and vigilance responses relative to controls. The magnitude of most behavioural responses (four of six considered) to elephant vocalizations were not significantly different than responses to leopards. These results suggest that megaherbivores can elicit strong non-trophic fear responses by ungulates and call to broaden frameworks on fear to consider dominant species, such as megaherbivores, as key modifiers of fear-induced interactions.