title: Diamond encapsulated photovoltaics for transdermal power delivery.
abstract: A safe, compact and robust means of wireless energy transfer across the skin barrier is a key requirement for implantable electronic devices. One possible approach is photovoltaic (PV) energy delivery using optical illumination at near infrared (NIR) wavelengths, to which the skin is highly transparent. In the work presented here, a subcutaneously implantable silicon PV cell, operated in conjunction with an external NIR laser diode, is developed as a power delivery system. The biocompatibility and long-term biostability of the implantable PV is ensured through the use of an hermetic container, comprising a transparent diamond capsule and platinum wire feedthroughs. A wavelength of 980 nm is identified as the optimum operating point based on the PV cell's external quantum efficiency, the skin's transmission spectrum, and the wavelength dependent safe exposure limit of the skin. In bench-top experiments using an external illumination intensity of 0.7 W/cm(2), a peak output power of 2.7 mW is delivered to the implant with an active PV cell dimension of 1.5 × 1.5 × 0.06 mm(3). This corresponds to a volumetric power output density of ~20 mW/mm(3), significantly higher than power densities achievable using inductively coupled coil-based approaches used in other medical implant systems. This approach paves the way for further ministration of bionic implants.
authors.affiliation: School of Physics, University of Melbourne, Victoria, Australia. Electronic address: arman.ahnood@unimelb.edu.au.
authors.forename: A
authors.initials: A
authors.lastname: Ahnood
authors.affiliation: School of Physics, University of Melbourne, Victoria, Australia; School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University, Victoria, Australia.
authors.forename: K E
authors.initials: KE
authors.lastname: Fox
authors.affiliation: School of Physics, University of Melbourne, Victoria, Australia; The Bionics Institute, Victoria, Australia.
authors.forename: N V
authors.initials: NV
authors.lastname: Apollo
authors.affiliation: School of Physics, University of Melbourne, Victoria, Australia.
authors.forename: A
authors.initials: A
authors.lastname: Lohrmann
authors.affiliation: School of Physics, University of Melbourne, Victoria, Australia; The Bionics Institute, Victoria, Australia.
authors.forename: D J
authors.initials: DJ
authors.lastname: Garrett
authors.affiliation: The Bionics Institute, Victoria, Australia; Department of Pathology, University of Melbourne, Australia.
authors.forename: D A X
authors.initials: DA
authors.lastname: Nayagam
authors.affiliation: School of Physics, University of Melbourne, Victoria, Australia; The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia.
authors.forename: T
authors.initials: T
authors.lastname: Karle
authors.affiliation: School of Physics, University of Melbourne, Victoria, Australia.
authors.forename: A
authors.initials: A
authors.lastname: Stacey
authors.affiliation: O'Brien Institute, Victoria, Australia; Faculty of Health Sciences, Australian Catholic University, Melbourne, Australia; Department of Surgery, St. Vincent's Hospital, University of Melbourne, Melbourne, Australia.
authors.forename: K M
authors.initials: KM
authors.lastname: Abberton
authors.affiliation: O'Brien Institute, Victoria, Australia; Faculty of Health Sciences, Australian Catholic University, Melbourne, Australia; Department of Surgery, St. Vincent's Hospital, University of Melbourne, Melbourne, Australia.
authors.forename: W A
authors.initials: WA
authors.lastname: Morrison
authors.affiliation: Centre for Sustainable Energy Systems, College of Engineering and Computer Science, The Australian National University, Canberra, Australia.
authors.forename: A
authors.initials: A
authors.lastname: Blakers
authors.affiliation: School of Physics, University of Melbourne, Victoria, Australia.
authors.forename: S
authors.initials: S
authors.lastname: Prawer
mesh_terms: D020099:Coated Materials, Biocompatible / Q000138:chemical synthesis*; D018130:Diamond / Q000737:chemistry*; D011211:Electric Power Supplies; D004735:Energy Transfer; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008422:Materials Testing; D019736:Prostheses and Implants; D012993:Solar Energy
chemical_list: D020099:Coated Materials, Biocompatible; D018130:Diamond
keywords: Energy harvesting; Photovoltaics; Transdermal power delivery