Synthesis of flexible and up-converting luminescent NaYF4:Yb,Er-PET composite film for constructing 980-nm laser-driven biopower

Abstract

One of the prerequisites for the development of wireless nanobiodevices (such as nanorobots) is to utilise an in vivo energy source as a biopower component that is continuously available in the operational biological environment. To address this problem, herein we have developed a new model of a 980-nm laser driven photovoltaic cell (hereafter abbreviated as 980LD-PC) by incorporating a flexible up-converting luminescent film and flexible amorphous silicon thin film photovoltaic cell. NaYF₄:Yb,Er-PET composite films are prepared by using film casting technology, and they exhibit excellent up-converting luminescence, flexibility and transparency. Subsequently, the composite film with NaYF₄:Yb,Er/PET weight ratio of 20% is adhered on the surface of a flexible amorphous silicon film solar cell for constructing a flexible 980LD-PC photovoltaic cell. Under the irradiation of a 980-nm laser (intensity: 720 mW cm⁻², area: 0.25 cm²) that is slightly lower than the conservative limit (726 mW cm⁻²) for human skin exposure, the resulting 980LD-PC exhibits strong up-converting luminescence, and it has a maximal electrical output of 94 μW. More importantly, after being covered with a layer of chicken skin (thickness: ca. 1 mm) as a model of biological tissue, 980LD-PC still exhibits bright up-converting luminescence and a maximal electrical output of 62 μW which is high enough to drive biological devices including in vivo nanorobots (power: at least 1 μW) and cardiac pacemakers (power: about 10 μW). This research paves the way for the development of novel flexible biopower sources to drive wireless nanobiodevices and other biodevices implanted under the human skin.