Cardiovascular Biomechanics and Ultrasound Laboratory
Imperial College London, Department of bioengineering

Menu Lab Home People Research Projects Publications Position Vacancy	Towards a Blood Pump with Low Blood Damage
	Blood pumps save countless lives every day, and include the implanted type (LVAD), those in the ICU (ECMO), and those in the surgical suite (heart-lung machine). However, they impose high stresses on blood and induce foreign surface reactions to cause thrombosis, and thromboembolic complications. We pursue various strategies and technologies to attain a blood pump with low blood damage. For example, we fabricate superhydrophobic and superhemophobic surfaces to enable slip flow in blood pump surfaces to reduce stresses, we seek new ways of pumping blood, such as using electro-active polymers and utilizing resonance in roller pumping.
	Superhydrophobic Blood Pumps We pursue the strategy of using superhydrophobic surfaces to enable slip flow to reduce fluid stresses in cardiovascular medical devices such as blood pumps. We have a holistic approach of fabricating novel biocompatible superhydrophobic materials, testing them for drag reduction, protein adsorption and hemocompatibility properties, using them in blood pumps, and performing computational simulations to understand the effects of using these material in the pumps. We were successful in fabricating a superhydrophobic material that is flexible, shape-customizable, and which has admirable durability and excellent drag reduction capabilities. Blood rolling off the SHP surface without stains Superior durability of the SHP material compared to alternatives Good drag reduction capabilities of the SHP material The effects of inserting superhydrophobic surfaces into a extracorporeal blood pump was investigated via computational simulations. We found that blood damage and fluid shear stresses could be reduced, the pumping pressure and pump efficiency could be increased. Simulations of a commercial blood pump head with superhydrophobic coatings
	References: - Li Z, Nguyen BL, Cheng YC, Xue JM, MacLaren G, Yap CH. "Durable, Flexible, Superhydrophobic and Blood-Repelling Surface for Use in Medical Blood Pumps." J. Mater. Chem. B. 2018;6(39):6225-33. - Lai CQ, Chia JWS, Chua WWC, Yap CH. "Near-Superhydrophobic Surface Reduces Hemolysis of Blood Flow in Tubes." RSC Advances. 2016; 6(67):62451-9
	Dielectric Elastomer Fluid Pump We investigated a special electro-active polymer, Dielectric Elastomer (DE), for use in fluid pumping. DE has the alias of "artificial muscle" as it has similar energy density and actuation strain capabilities as natural muscles. DE is also interesting because it exhibits electro-mechanical instability (commonly known as the snap-through phenomenon), exhibiting a reversible large stretch due to natural instabilities, which can be tapped into to drastically enhance pumping volume. We demonstrated the use of reversible snap-through for fluid pumping in vitro, and discovered the conditions necessary for this to happen. We also laid down the theoretical framework for DE snap-through fluid pumping, and demonstrated experimental pressure-volume curves that fits this theory. Further, we proposed methods to counter the durability limitations and excessive viscoelastic properties of DE, such as adding highly elastic material to it to form a composite, and we proposed design methods that enable DE fluid pumps to snap-through under a wider range of pressures, and under high adverse pressure gradients.
	Dual-membrane design that enables high volume per cycle pumping even under unfavourable pressure conditions.
	References: - Li Z, Zhu J, Foo KCC, Yap CH. "A Novel and Robust Dual-Membrane Dielectric Elastomer Actuator for Large Volume Fluid Pumping via Snap-through". Appl. Phys. Lett. 2017 Nov 20;111(21):212901. - Li Z, Wang Y, Foo KCC, Godaba H, Zhu J, Yap CH. "The Mechanism for Large-Volume Fluid Pumping via Reversible Snap-Through of Dielectric Elastomer." J Appl Phys. 2017 Aug 28;122(8):084503 - Wang YX, Li Z, Qin L, Caddy G, Yap CH and Zhu J. "Dielectric Elastomer Fluid Pump of High Pressure and Large Volume Via Synergistic Snap-Through" J. Appl. Mech. 2018 Oct 1; 85(10):101003 - Ho S, Banerjee H, Foo YY, Godaba H, Aye WMM, Zhu J, Yap CH. "Experimental Characterization of a Dielectric Elastomer Fluid pump and Optimizing Performance via Composite Materials." J Intell Mater Syst Struct. 2017 Dec;28(20):3054-65.