Vertically and Horizontally Drawing Formation of Graphite Pencil Electrodes on Paper by Frictional Sliding for a Disposable and Foldable Electronic Device

Abstract

The objective of this study is to fabricate an electrode by frictional sliding caused by a rough paper surface. The pressure exerted during drawing induces adsorption of the graphite particles by the rough paper and simultaneously reduces the surface roughness of the paper electrode. Repetitive drawing in one-way direction reduced the roughness of the paper surface, decreasing the grain boundaries of graphite. This increases the electron pathway at the electrode, thus reducing the resistance to less than 50 Ω. At the same time, repetitive drawing could confirm that unstable errors caused by the hand could help converge within a certain margin of error. We quantified the relationship between pressure and resistance when drawing on the electrode using a pencil hardness tester. In addition, the electrodes formed by repeated drawing generated a new surface grain and boundary, parallel to the drawing direction, and changed the electrode characteristics with respect to the drawing direction. The grain boundary difference based on the drawing direction was measured via a heating test of the foldable device, a sound pressure level, and laser scattering vibrometer measurements of a linear speaker. The fabricated graphite electrodes can be used in disposable foldable paper electronics because they are prepared using inexpensive materials.

Simultaneous quantitative detection of hematocrit and hemoglobin from whole blood using a multiplexed paper sensor with a smartphone interface

“…47 This promotes electrical conductivity and electron transfer, and hence, is potentially amenable to electrically-mediated sensing. 48,49 The automated graphite dispensing could thus be transformed into an unskilled handicraft, wherein the 8B graphite pencil (Camlin, 4 mm diameter) was found to be adequate to fill the designated area by exfoliation using freehand sketching (see Fig. 1B).…”

“…For instance, the graphitic trace thus obtained by the direct exfoliation technique forms a conductive carbon track which provides high electrical conductivity, electrochemical stability, and large active electrode surface area due to the irregular pencil graphite surface morphology. 48,49 Moreover, the rough surface of the electrode enhances the effective surface area as compared to the electrode surface obtained by photolithography, sputtering, thermal evaporation, screen printing, etc. This inhibits electrode polarization phenomena that otherwise are known to manifest as an undesirable feature for the measurements undertaken in the lowfrequency region of the impedance spectra.…”

“…42 Errors due to the false decrement of Hb values on account of inadequate hemolysis or sample mixing have also been reported in the context of using standard correlations for determining the Hct level. 43 Consequently, such a correlation-based methodology [48][49][50][51] appears to be scientifically flawed as well as technologically challenged. In contrast, simultaneous yet independent experimental measurements of the Hct and Hb levels appear to be a more robust foundation of obtaining the desired hematological information to facilitate appropriate clinical decision making.…”

Cr2O3–TiO2-Modified Filter Paper-Based Portable Nanosensors for Optical and Colorimetric Detection of Hydrogen Peroxide

“… 35 Recently, filter paper has drawn much interest as a potential material for sensors and devices in analytical and clinical chemistry because of its versatility, high abundance, and low cost. 36 These analytical devices can be integrated in a manner that is flexible, portable, disposable, and easy to operate. Following the invention of paper chromatography in the early 21st century, diagnostic devices based on paper began to emerge.…”

“…Filter paper-based sensors could meet the current objectives of a viable low-cost and portable device in addition to offering high sensitivity and selectivity and multiple analyte discrimination . Recently, filter paper has drawn much interest as a potential material for sensors and devices in analytical and clinical chemistry because of its versatility, high abundance, and low cost . These analytical devices can be integrated in a manner that is flexible, portable, disposable, and easy to operate.…”