The human being has used its own body to generate mechanical energy from the dawn of time. Moving the muscles of the body allows us to perform many daily activities, whether running, hunting, carrying weights or plowing the fields. But what about other internal muscle movements, such as those caused by incessant heartbeats and breathing? Is it possible to take advantage of that energy, generated constantly and involuntarily?
A Turkish young woman named Canan Dagdeviren, PhD from the university of Illinois at Urbana – Champaign (USA), believes that not only is it possible but rather also very necessary. Dagdeviren has invented an implantable device capable of collecting, storing and transforming the energy produced by the motion of the heart, diaphragm and lungs into electrical current. This small, internal generator could be used, for example, to feed biomedical devices like a pacemaker.
Her invention, named PZT MEH, is shaped like a thin sheet which can be placed directly onto the surface of an organ. It is composed by several elements: a substratum of soft,flexible, biocompatible material; an extremely thin, electric component made of a material called lead zirconate titanate (PZT) which is imprinted on the substratum and generates electrical current as it changes shape; an electrical rectifier which modifies the obtained electrical current, allowing it to be stored; and a micro-battery.
The connection between the PZT and the battery is achieved through an anisotropic, conductive tape, a very thin and light type of cable. Each time the heart muscle contracts rhythmically, something which happens about 40 million times a year, -the PZT component curves then relaxes, producing a small electric current due to its piezoelectrical properties. Once rectified, this electrical current can either be consumed or stored in the micro-battery
Dagdeviren explains that one of the greatest advantages of these flexible nano-generators as compared to other existing ones is precisely that they are soft, thin and can bend and twist; this allows a great adaptability to the natural movements of an organ “in a way that it does not produce any significant restriction in these movements”. That is to say, it is not hard or heavy nor does it hinder the natural rhythm of the heart, as can be the case with other devices built using silicon.
After four years of working with engineers, computer specialists and surgeons, Dadgeviren and her team presented the PZT MEH on February 2014 in the journal PNAS. Tests had been performed previously on live animals - cows, sheep and pigs - with satisfactory results in terms of the system´s placement and performance in the heart, lungs and diaphragm.
In order to ensure the biocompatibility of all its parts, Dadgeviren’s device is encapsulated within a thin layer of polyimide, a polymer that isolates it from bodily fluids and minimizes the risk of electrical failure or immune reactions. In addition, the researchers conducted an experiment to determine whether new muscle cells could grow normally on the PZT MEH. After 9 days, the culture cells had multiplied, covering the PZT MEH´s surface and results showed that more than 96% of the new cells were viable.