In this paper, a facile and low-cost “pencil-drawing” method is exploited for writing electrodes on filter paper to
fabricate an electrochemical paper-based analytical device. Unlike other techniques using inks or pastes, the
three-electrode system can be prepared directly by drawing with nothing more than pencils and paper. The
optimization using ferricyanide as the redox probe showed that the device fully drawn with 6B grade pencil
possesses excellent electrochemical properties and sensor-to-sensor reproducibility in spite of its truly simple
fabrication process. Experimental results demonstrated that the proposed device could be utilized for quantification
of dopamine with high sensitivity and no interference from ascorbic acid and uric acid, which are normally present
in biological fluids. Human urine and blood serum samples were analyzed using the proposed device as proof of
concept. Such fully-drawn sensors are flexible, portable and disposable, represent a cheap and environmentally
friendly approach that can be rapidly and easily fabricated without any specialized materials, affording great
convenience for practical use in resource-limited or emergency situations.