A ventricular assist device (VAD) is a mechanical circulatory device used to pump blood in series or in parallel with the native heart in the cases of extreme heart failure [5]. VADs consist of a pump, and electric controller, and a power source. For the purpose of this website, the pump element will be the central focus of discussion. The pumps can either pump blood in a pulsatile manner, like the heart, or continuously.  The following video further explains the concept of VADs [6]:

 
Piezoelectric materials, due to their efficiency and size, have also been used to build VADs. Research published by Williams et al. showed the developed of a new VAD using piezoelectric ceramic elements. This particular device is placed in series with the natural heart. It consists of two piezoelectric elements, which are coordinated with the heart rate of the subject. This is accomplished via the loading of high density masses onto the piezoelectric elements to yield resonant frequencies which match a particular heart rate [7]. A pulsatile flow is established due to the subsequent compression from the benders on the thin-walled tubing carrying the blood. The figure below shows the functional schematic and a photograph of the device [7]:



The piezoelectric elements are composed of zironate titanate ceramic strips; while the weights, used to yield the desired resonant frequencies, are made of tungsten alloy and weigh 0.44 kg [7]. One end of the element is clamped, while the other end is supported by dry ball bearings with stationary shafts. These shafts hold the polyether polyurethane segmented tubing, which carries the blood. The peak driving voltage for the piezoelectric elements is achieved at a peak level of 20 V/mil, which has been proven to prevent material failure [7].

The device offers the advantage of simple fabrication, low power consumption than earlier designs (see intra-aortic balloon pump), and noiseless electrical operation. In addition, the piezoelectric device is non-invasive and uses only 5% of the power required by pneumatic pumps [7].

Another VAD exploits the properties of a piezoelectric material to ensure proper function. The piezoelectric material lies within an intracardiac pump catheter and acts as a differential piezoresistive pressure sensor [8]. The device monitors variances in pressure during use and provides adequate feedback for corrective action. The figure below shows a picture of the device [8]: