Photovoltaic cells operate under the skin for implants

September 09, 2019 //By Julien Happich
Researchers at the Laboratory of Organic Electronics from Linköping University have used thin-film photovoltaic cells under the skins to power ion pumps. The PV cells use red light and can operate hrough 1.5cm of soft tissues.
Thin-film photovoltaic cells under the skin use red light and can operate through 1.5cm of soft tissues.

The researchers at the Laboratory of Organic Electronics from Linköping University are using selective electrophoretic ion transport across an ion exchange membrane to create an electronic ion pump implants that allow the precise and convection-free delivery of small-sized ionic species. By applying an electric field along the membrane, specific ions are transported from one end to the other with a negligible amount of solvent being co-transported with the ions.

Schematics of the integrated OPV and OEIP components on thin parylene-C substrates.

Thus far, thin organic electronic ion pumps (OEIP) have been used in vivo to modulate sensory functions through electrophoretic drug delivery, or to alleviate epileptic seizures through the local delivery of neurotransmitters. But all implementations reported in literature relied on external power supplies (hence wiring), which increases the chances of inflammation, especially for long-term therapy applications.

In a paper titled "Wireless organic electronic ion pumps driven by photovoltaics” published in Nature’s journal of Flexible Electronics, the researchers report a thin OEIP coupled to an organic photovoltaic (OPV) driver, on a flexible carrier. The whole implant can be addressed by red light within the tissue transparency window, removing the need for external wiring.

In order to obtain the 2.5–4.5 V necessary for operating the high-resistance electrophoretic ion pumps, the researchers arranged organic thin-film bilayer photovoltaic pixels in series and in vertical tandem. To prove the concept, they laminated the device onto a finger and were able to drive it with a red LED emitting through the finger’s thickness.

As the authors explain, the OPV active material was chosen to strongly absorb red light in the tissue transparency window (600–700 nm), and by virtue of their high absorption coefficient materials, could be designed to a thickness under 300 nm so the overall implant thickness could be minimized while remaining flexible.

Linköping University -

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