Novel heart valve leaflet designs with stiff polymeric materials and biomimetic kinematics

Despite continuous efforts to improve the robustness of cardiac valve implants,neither bioprosthetic nor mechanical valves fulfill both hemodynamic and durability requirements.This study discussed novel flexible leaflet designs,focusing on polymeric materials with proven hemocompatibility,such as polyether ether ketone,of much higher stiffness than native tissue,aiming at optimal valve implants.A biomimetic valve with a single-curvature belly-curve(B-C)was used as a reference for new design variants with a double-curvature B-C with varying radii.Soft(13.2 MPa)and stiff(2.4 GPa)leaflet materials and different thicknesses were studied using lean simulations and in vitro experiments under physiologic hemodynamic conditions.The performance was assessed using opening pressure(OP)and orifice area(OA).The latter was determined by a newly developed automatized image processing tool.Experimental trends are in agreement with simulations and demonstrated that a buckling-inspired double-curvature leaflet design significantly enhances the trileaflet valve opening behavior,which is particularly advantageous for stiffer leaflet materials.Compared to the reference,the best-performing variant showed an OP improvement of 47%and 44%based on simulations and experiments,respectively.In contrast,the achieved mean pressure differential was directly comparable to state-of-the-art bioprosthetic valves.The OA was slightly reduced for new variants but still in the satisfying range.

An in vitro demonstration of a passive,acoustic metamaterial as a temperature sensor with mK resolution for implantable applications

Wireless medical sensors typically utilize electromagnetic coupling or ultrasound for energy transfer and sensor interrogation.Energy transfer and management is a complex aspect that often limits the applicability of implantable sensor systems.In this work,we report a new passive temperature sensing scheme based on an acoustic metamaterial made of silicon embedded in a polydimethylsiloxane matrix.Compared to other approaches,this concept is implemented without additional electrical components in situ or the need for a customized receiving unit.A standard ultrasonic transducer is used for this demonstration to directly excite and collect the reflected signal.The metamaterial resonates at a frequency close to a typical medical value(5 MHz)and exhibits a high-quality factor.Combining the design features of the metamaterial with the high-temperature sensitivity of the polydimethylsiloxane matrix,we achieve a temperature resolution of 30 mK.This value is below the current standard resolution required in infrared thermometry for monitoring postoperative complications(0.1 K).We fabricated,simulated,in vitro tested,and compared three acoustic sensor designs in the 29-43℃(~302-316 K)temperature range.With this concept,we demonstrate how our passive metamaterial sensor can open the way toward new zero-power smart medical implant concepts based on acoustic interrogation.