There is an increasing need for wearable diagnostic sensor devices and for enzymatic biofuel cells (EBFCs) as efficient power sources. In this study, a six-glucose/O 2 biofuel cell array connected in series was fabricated by screen printing as a self-powered glucose sensor exhibiting an electromotive force of 3.2 V. Porous carbon electrodes were formed by screen printing of MgO-templated carbon on water-repellent paper to improve the performance of the cathode and thus prevent it from being the limiting step. The bioanode contained glucose oxidase as a catalyst and tetrathiafulvalene as a mediator, and the cathode contained bilirubin oxidase as an oxygen reduction catalyst. A good linear relationship was obtained between the output of EBFCs and glucose concentration (1-25 mM), which contains the range of urine glucose levels. The artificial urine components did not interfere with the output of the EBFC, but it was limited by low ion conductivity and low buffer capacity.

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We name the Printable Electrochemistry for the development field of printable electrochemical devices [1,2]. Recently, we focus on several paper-based fully-printable electrochemical devices such as biofuel cell [3], biosensor [4] and reference electrode [5].  Paper-based biofuel cell have been attracted as a potential application as energy harvesting power sources in Internet of things (IoT) field [6,7]. In the present study, we newly developed paper-based wearable biofuel cell array fabricated by screen-printing.  Figure 1 shows a schematic illustration of one of our wearable biofuel cell array. The paper-based biofuel cell array exhibited a maximum power density of 1 mW. The present flexible paper-based biofuel cell is highly applicable to the development of low cost, flexible, ubiquitous energy devices. In the present study, we discuss the characteristics of the wearable biofuel cells in detail. [1] I. Shitanda et al., Electrochim. Acta 54 (2009) 4933. [2] I. Shitanda et al., Sens. Actu. B: Chem. 160 (2011) 1606. [3] I. Shitanda et al., Chem. Commun. 49 (2013) 11110. [4] I. Shitanda et al., Chem. Lett. 42 (2013) 1369. [5] I.Shitanda et al., Analyst, 140 (2015) 6481. [6] Claudia W. Narváez Villarrubia et al., Electrochem. Commun, 45 (2014) 44. [7] Carolin Lau et al., Int. J. Hydrogen. Energy, 42 (2015) 14661. Figure 1