Self-organized tubular metal oxide nanostructures, synthesized through straightforward and efficient techniques, have resulted in many breakthroughs yet are underutilized in the energy and microdevice field. Here we demonstrate the fabrication and characterization of unique biocompatible energy storage devices that use self-assembled titanium dioxide (TiO₂) and a physiological fluid such as PBS as the electrolyte, without any need of toxic conventional acidic or alkaline electrolytes. Achieving high capacitance through the use of a neutral aqueous electrolyte, combined with the biocompatibility of TiO₂ and Ti films opens up new avenues for the investigation of these materials for energy harvesting applications in biological media. We also describe unadulterated anodized TiO₂ with higher volumetric capacitance (220 F cm^-3) and energy density (5.12 mWh cm^-3) values compared to the conventional carbon based micro-supercapacitor devices.

Figure 1. (a) Cyclic performance of TNTA device obtained by CV test at scan rate of 20 mVs^-1 along with the 2^nd and 2000^th cycles of the CV performances in two electrolytes (inset), (b) In-vitro biocompatibility of TNTAs; NIH 3T3 cells exposed to TNTAs for 24 hours did not exhibit a decrease in cell viability compared to untreated cells.