Cellulose microfluidic pH boosting on copper oxide non-enzymatic glucose sensor strip for neutral pH samples

Abstract

A cellulose microfluidic pH boosting layer adapts a non-enzymatic copper oxide glucose sensor strip for neutral pH samples. This adaptation allows the non-enzymatic technology to realize in-situ glucose measurements. A three-electrode system is constructed to test samples in a classical electrochemical cell, and in a sensing strip to test the microfluidic system. The system consists of copper oxide as working electrode, and silver and carbon paints as reference, and counter electrodes, respectively. The fabrication of the pH-boosting layer is made with natural cellulose. Within this layer are NaOH crystals, grown by a drying processes after immersion of cellulose in a concentrated solution of NaOH. The microfluidic layer is placed on top of the sensing electrodes, and while it transports the fluid sample to the sensing electrodes, the fluid dissolves the NaOH crystals, increasing the pH of the sample. This change allows the non-enzymatic mechanism to sense the glucose concentration in the fluid. Our system shows the capability to measure glucose in samples with neutral pH and human blood with a sensitivity of 70 μA/mM cm2, enough to distinguish between hypoglycemia and hyperglycemia.