Series-Connected Flexible Biobatteries for Higher Voltage Electrical Skin Patches

Abstract

A totally organic, flexible higher voltage enzymatic biobattery is demonstrated by series connection of carbon fabric-based biobatteries composed of a fructose dehydrogenase-modified anode and a bilirubin oxidase-modified cathode. The fructose/O2 biobattery was divided and connected so as to maintain the original size (total electrode size: 2 cm2). The series-connected four quarter biobatteries showed increased voltage and current (0.6 V, 30 μA → 1.5 V, 80 μA) for an external load of 20 kΩ, which is a typical skin resistance. The divided batteries were put inside a flexible ion-insulating frame to avoid short-circuit between cells and electrically connected by soft hydrophobic leads that prevented ionic connection by wetting. Because the developed higher voltage biobattery maintains its small size and flexibility, it can even be put on a finger joint and serve to drive a wrist watch.

Transdermal electroosmotic flow generated by a porous microneedle array patch

“…The piece of CNT-modified CF was immersed in a 1 mL stirred McIlvaine buffer (pH 5.0) containing 10 mg FDH enzyme (FCD-302, 145 U mg −1 from Gluconobactor, Toyobo) for 4 h at 4 °C. Also, the BOD-modified cathode was prepared according to the previous studies 11 , 65 . Briefly, the modification of CNTs on CF was repeated four times to get a thicker CNT coating, followed by the modification of 10 mg BOD (2.5 U mg −1 , from Myrothecium, Amano Enzyme).…”

“…Importantly, a 100 µL of ethanol dispersion of 4 mg/mL CNT and 12.5 mg/mL PTFE (PTFE, FUJIFILM Wako Pure Chemical) was further coated by dropping twice to ensure hydrophobicity for efficient reduction of ambient O 2 . As explained in the recent report 65 , four couples of the FDH-anode (1 cm 2 ) and the BOD-cathode (1 cm 2 ) were series-connected to boost the output voltage four times. The enzyme electrodes were connected using hydrophobically treated carbon fabrics (0.55 Ω/sq), and these connectors served as the internal resistor (totally <10 Ω).…”

“…5d . We have used McIlvaine buffer for the investigation of an enzymatic biobattery, especially to maintain the activity of enzyme electrodes for a longer time 65 , 78 . The cross-sectional fluorescence image of the skin at anode was analyzed with ImageJ after a 1 h application of the enzymatically produced EOF around 0.2 mA/cm 2 .…”

“…A userfriendly iontophoresis skin patch requires the integration of a lightweight and safe power source to drive the transdermal electroosmosis. Enzymatic biobatteries [65][66][67][68][69] , which utilize enzymes as an electrocatalysis for anodic oxidation of biochemical fuels like sugars and cathodic reduction of atmospheric O 2 , can be an option for such an organic disposable power source for an iontophoretic transdermal patch 11 . Figure 5a illustrates the combination of the PMNs and a fructose/O 2 biobattery, which consists of a series-connected array of four couples of anode and cathode electrodes in order to generate sufficient transdermal EOF by the boosted voltage 65 .…”

“…Enzymatic biobatteries [65][66][67][68][69] , which utilize enzymes as an electrocatalysis for anodic oxidation of biochemical fuels like sugars and cathodic reduction of atmospheric O 2 , can be an option for such an organic disposable power source for an iontophoretic transdermal patch 11 . Figure 5a illustrates the combination of the PMNs and a fructose/O 2 biobattery, which consists of a series-connected array of four couples of anode and cathode electrodes in order to generate sufficient transdermal EOF by the boosted voltage 65 . Figure 5b depicts the typical performance of the biobattery composed of the fructose dehydrogenase (FDH)-modified flexible carbon fabric (CF) anodes (1.0 cm 2 ), and the bilirubin oxidase (BOD)-modified CF cathodes (1.0 cm 2 ), taken on a cotton cloth containing 0.2 M D-fructose.…”