Abstract
Today’s smallest energy storage devices for in-vivo applications are larger than 3 mm3 and lack the ability to continuously drive the complex functions of smart dust electronic and microrobotic systems. Here, we create a tubular biosupercapacitor occupying a mere volume of 1/1000 mm3 (=1 nanoliter), yet delivering up to 1.6 V in blood. The tubular geometry of this nano-biosupercapacitor provides efficient self-protection against external forces from pulsating blood or muscle contraction. Redox enzymes and living cells, naturally present in blood boost the performance of the device by 40% and help to solve the self-discharging problem persistently encountered by miniaturized supercapacitors. At full capacity, the nano-biosupercapacitors drive a complex integrated sensor system to measure the pH-value in blood. This demonstration opens up opportunities for next generation intravascular implants and microrobotic systems operating in hard-to-reach small spaces deep inside the human body.
Highlights
Today’s smallest energy storage devices for in-vivo applications are larger than 3 mm[3] and lack the ability to continuously drive the complex functions of smart dust electronic and microrobotic systems
The small volume (1 × 10−3 mm3 = 1nL) of the nBSC is achieved by self-assembling planar structures into a 3D compact tubular geometry, which in turn allows for stable operation under hemodynamic conditions with varying temperatures, pulsating blood flow and self-protection against external forces
We find that the capacitance of the nBSC varies as a function of the electrolyte potential of hydrogen (pH)
Summary
Today’s smallest energy storage devices for in-vivo applications are larger than 3 mm[3] and lack the ability to continuously drive the complex functions of smart dust electronic and microrobotic systems. The generated protons can be used by living cells to perform metabolism[12] or by redox enzymes and glucose to trigger active catalytic reduction These complex biological reactions release energy which nBSCs can harness to compensate for any self-discharge[10,11,12,13]. By integrating three charged nBSCs with a nBSC based ring oscillator, we realize a self-powered sensor for monitoring the pH of blood This demonstration promotes nBSCs as excellent candidates for miniaturized biocompatible intravascular implants, in vivo smart dust[1,2,3,4,5,6] and microrobotic systems[7] with broad application potential in the personalized healthcare sector. The quasielectronic and ionic passivation provided by the SU8 photoresist and PVA separator enable the nBSCs to reach a single device peak voltage of 1.6 V without any gas evolution in all aqueous electrolytes (Fig. 1i, Supplementary Fig. 8, 9, Note 3 and Supplementary Movie 1)
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