D. Liu, G.-Y. Li, C. Su, Y. Zheng, Y.-X. Jiang, L.-X. Qian, and Y. Cao. 2018. “
Effect of ligation on the viscoelastic properties of liver tissues.” Journal of Biomechanics, 76.
AbstractIt has been reported that ex vivo viscoelastic properties of liver tissues usually differ from those measured in in vivo state due to the reasons such as the effects of perfusion, temperature, and native pre-stress. Therefore, the development of an appropriate ex vivo protocol, which enables the measurement of liver mechanical properties close to those in vivo, is of great importance and has been pursued over the years. In this paper, we propose a simple protocol by ligating the liver when performing ex vivo indentation relaxation tests. Our results show that the viscoelastic kernel function, which measures the intrinsic time-dependent mechanical behavior of a viscoelastic material, determined with the present protocol can describe the in vivo viscoelasticity of liver tissues well in comparison with the ex vivo result measured on a liver without ligation and that obtained in vitro. The performance of the protocol reported here is similar to the ex vivo perfusion system developed by Kerdok et al. (2006). However, the present experimental set-up is much easier to realize.
Y.-L. Liu, D. Liu, L. Xu, C. Su, G.-Y. Li, L.-X. Qian, and Y. Cao. 2018. “
In vivo and ex vivo elastic properties of brain tissues measured with ultrasound elastography.” Journal of the Mechanical Behavior of Biomedical Materials, 83.
AbstractDetermining the mechanical properties of brain tissues is essential in the field of brain biomechanics. In this paper, we use ultrasound-based shear wave elastography to measure both in vivo and ex vivo elastic properties of brain tissues. Our results demonstrate that the shear modulus from in vivo measurements is about 47% higher than that given by the ex vivo measurements (p value = 0.0063). The change in ex vivo elastic properties within 60-min post-mortem is negligible. The results also show that within 60-min post-mortem and in a temperature range of 37–23 °C, the elastic properties of brain tissues approximately linearly depend on the temperature in both cooling and re-heating processes.
G.-Y. Li, G. Xu, Y. Zheng, and Y. Cao. 2018. “
Non-leaky modes and bandgaps of surface acoustic waves in wrinkled stiff-film/compliant-substrate bilayers.” Journal of the Mechanics and Physics of Solids, 112.
AbstractSurface acoustic wave (SAW) devices have found a wide variety of technical applications, including SAW filters, SAW resonators, microfluidic actuators, biosensors, flow measurement devices, and seismic wave shields. Stretchable/flexible electronic devices, such as sensory skins for robotics, structural health monitors, and wearable communication devices, have received considerable attention across different disciplines. Flexible SAW devices are essential building blocks for these applications, wherein piezoelectric films may need to be integrated with the compliant substrates. When piezoelectric films are much stiffer than soft substrates, SAWs are usually leaky and the devices incorporating them suffer from acoustic losses. In this study, the propagation of SAWs in a wrinkled bilayer system is investigated, and our analysis shows that non-leaky modes can be achieved by engineering stress patterns through surface wrinkles in the system. Our analysis also uncovers intriguing bandgaps (BGs) related to the SAWs in a wrinkled bilayer system; these are caused by periodic deformation patterns, which indicate that diverse wrinkling patterns could be used as metasurfaces for controlling the propagation of SAWs.