Biomechanics of the Intrauterine Growth Restriction Placenta Disease, and Using Artificial Muscles to Make Artificial Hearts

Tarih: 23.01.2018
Yer: Biyomedikal Mühendisliği Enstitüsü, AZ-19

23 Ocak (SALI)
13.30 - 14.30
Biyomedikal Mühendisliği Enstitüsü, AZ-19,  
Boğaziçi Üniversitesi Kandilli Kampüsü, İstanbul

Dr. Yap Choon Hwai


About the Seminar

I will present two aspects of my lab’s work, if time permits: the biomechanics of placenta during intrauterine growth restriction (IUGR) disease, and using artificial muscles to make artificial hearts.

IUGR is a disease of the placenta that restricts blood flow, leading to insufficient nutrients and oxygen transfer. Babies have 5-10x higher mortality, and lifelong morbidities such as neuro-maldevelopment, hypertension, diabetes, and heart diseases. We currently have no proven strategy to treat or prevent this. If detection is successful, early delivery of the baby can improve outcomes, but current detection rates are low. We performed a series of biomechanics investigation of the placenta, and propose that ultrasound strain elastography could be an improved method to detect IUGR, via detecting changes to the placenta mechanical properties. We first performed mechanical testing of placenta tissues to understand their mechanical properties, so as to optimize the protocol of placenta strain elastography. We demonstrated that a motorized control of ultrasound transducer, using an external polymeric pad as a standardized reference layer, and performing elastography at specific strain rate conditions could improve results. Next, we testing placenta chorionic arterial mechanical properties, and found that severe IUGR arteries have increased distensibility, which could explain the changes in umbilical arterial flow waveforms. We also found that umbilical vascular wall shear stress (WSS) did not differ between IUGR and normal pregnancies, that umbilical arteries maintained a WSS homeostasis, but umbilical veins did not, and that the spiral anatomy of umbilical arteries served to maintain hemodynamic constancy despite umbilical cord bending

In terms of artificial hearts, we investigated the use of a novel robotics material, dielectric elastomer, otherwise known as “artificial muscles” to pump fluids, and laid down foundational work to enable this. Dielectric elastomers could generate high strains and has high energy density per weight. We were able to utilize an electro-mechanical instability, known as “snap-through”, to generate large volume per cycle fluid pumping, and provided a theoretical framework for the pressure-volume work loop of this type of fluid pumping. We further proposed a composite dielectric elastomer material to counter high viscoelasticity of the material, a dual-membrane pump design to enable functionality at low pressure environments, and serial-pump designs to enable pumping against high pressure gradients.

About the Speaker

Dr. Yap Choon Hwai graduated with PhD from Georgia Institute of Technology, and worked as a postdoctoral scholar in University of Pittsburgh School of Medicine. He is currently an Assistant Professor in the Department of Biomedical Engineering in the National University of Singapore. Part of his research focus on the mechanics of prenatal cardiovascular system, and how abnormal blood flow mechanical force environment may be the cause of congenital heart malformations. His lab is the first to perform computational fluid dynamics (CFD) of human fetuses based on clinical ultrasound imaging, and pioneered a novel 4D imaging techniques with high-frequency ultrasound for image-based CFD of small animal embryonic hearts. Another part of his research is to fabricate low-thrombosis blood pumps using novel surface coating technologies.