Every day, countless lives are saved by blood pumps, including those that have been implanted and those used in the Intensive Care Unit (ICU), in heart surgery and during hemodialysis. Blood pumps, however, damage blood by exposing it to high stresses, causing platelet activation and hemolysis, which leads to blood clots. For example, seven percent of ICU patients on the extracorporeal membrane oxygenation (ECMO) blood pump suffer from severe hemolysis, which increases the mortality rate by six times. Another study shows that eighteen percent of left ventricular assist device (LVAD) patients suffer from hemolysis, which reduces one-year survivability from eighty-nine percent to thirty-nine percent.
Despite blood pump industry innovations, such as magnetic levitated impellers and wash-out designs, pump blood damage remains a major medical challenge. We pursue varied strategies to address this problem. On the materials side, we explore the use of superhydrophobic surfaces to coat blood pumps. Superhydrophobic surfaces enable blood fluid to slip past their surface with greatly reduced drag forces, decreasing blood stresses to minimize blood damage. We have fabricated superhydrophobic materials that can retain superhydrophobicity despite harsh abrasion test conditions and substantially reduce drag forces. We also showed in preliminary experiments that such surfaces can reduce hemolysis. Further, we investigated the use of a novel robotics material, dielectric elastomer, to make pulsatile blood pumps. Dielectric elastomer can give controlled deformations when given a voltage, via electrostatic attractive forces, and it has been hailed as artificial muscles. It was thus fitting that we attempt to use it as artificial heart muscles to make an artificial heart.
We developed strategies to use giant deformations (or the snap-through phenomenon) of dielectric elastomers to pump liquids, and strategies to make the snap-through mechanism work under varied physical conditions. We have also investigated alternative fluid pumping mechanisms. For example, we developed an under-occluded roller pumping mechanism, where the drastic under-occlusion reduced blood damage, and we used resonance effects (impedance pumping) to prevent loss of pumping efficiency. We thus named this pumping mechanism the roller-impedance pump.
Dr. Yap Choon Hwai graduated with a 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 focuses on the mechanics of the prenatal cardiovascular system and how an abnormal blood flow mechanical force environment may be the cause of congenital heart malformations. Another part of his research involves the fabrication of low-thrombosis blood pumps using novel surface coating technologies and via novel fluid pumping mechanisms.