Piezoelectric device comprising a membrane comprising fibres of a polyhydroxyalkanoate
A piezoelectric device includes a membrane having fibres of a polyhydroxyalkanoate (PHA), having average diameter between 100 nm and 2000 nm, and at least one oxide having piezoelectric properties in a subdivided form having at least one average size between 1 nm and 100 nm. Preferably, the PHA fibres are produced by electrospinning. Advantageously, demonstrating good piezoelectric properties and considering that the piezoelectric device includes PHA, a biodegradable and biocompatible material, the device can be used in biological systems, for example in flexible micro-actuator systems for drug delivery and in the engineering of biological tissues (such as, for example, in pacemaker devices).
1. A piezoelectric device comprising a membrane comprising fibres of a polyhydroxyalkanoate (PHA), having average diameter comprised between 100 nm and 2000 nm, and at least one oxide with piezoelectric properties in a subdivided form having at least one average size comprised between 1 nm and 100 nm;
wherein the oxide has at least one binding agent on its surface;
wherein the at least one binding agent is a hydrophilic binder, selected from: hydrocaffeic acid, polyethylene glycol derivatives, amino acids, proteins, vitamins, carbohydrates and lignin derivatives; or
a lipophilic binder, selected from: N-(3,4-dihydroxyphenethyl) dodecanamide, hydroxamic acids, amides, acetates, carboxylic acids with aliphatic chains with a number of atoms of carbon comprised between 6 and 16.
2. The device according to claim 1 , wherein the PHA is a polymer containing repeating units of formula (I):
—O—CHR 1 —(CH 2 ) n —CO— (I)
where:
R 1 is selected from: C 1 -C 12 alkyls, C 4 -C 16 cycloalkyls, C 2 -C 12 alkenyls, optionally substituted with at least one group selected from: halogen (F, Cl, Br), —CN, —OH, —OOH, —OR, —COOR (R=C 1 -C 4 alkyl, benzyl);
n is zero or is an integer from 1 to 6.
3. The device according to claim 2 , wherein the PHA is a polyhydroxybutyrate (PHB).
4. The device according to claim 1 , wherein the oxide is selected from: barium titanate (BaTiO 3 ), zinc oxide (ZnO), aluminium nitride (AlN), gallium nitride (GaN), cadmium sulfide (CdS), and is used in a subdivided form, preferably in the form of spherical nanoparticles, nanowires, nanotubes, nanobelts or nanorods.
5. The device according to claim 1 , wherein the oxide is present in a concentration comprised between 1% and 30% by weight, the % being expressed with respect to the overall weight of the membrane.
6. The device according to claim 1 , wherein the binding agent is present in a concentration comprised between 10% and 30%, the % being expressed with respect to the total weight of the oxide bound to the binding agent.
7. Use of the piezoelectric device according to claim 1 in piezoelectric energy transducers.