Enzyme-Free glucose detection in sweat using 2D inkjet-printed cobalt sulfide anchored on graphene in a paper-based microfluidic device.

Notwithstanding the significant advancements in the fabrication of flexible sensors capable of continuously detecting glucose levels in the human body, using conventional manufacturing techniques to create flexible sensors with excellent sensitivity at a low cost is still difficult. This paper introduces a low-cost, high-sensitivity glucose sensor (CoS/LPEG) that is prepared by combining liquid-phase exfoliated graphene (LPEG) and cobalt sulfide (CoS) for the first time through Inkjet printing. The glucose sensor demonstrates two linearity ranges in the glucose concentration ranges of 0.001-6.57 mM and 6.57-13.32 mM in NaOH, with sensitivities of 1046 μA mM cm and 477.78 μA mM cm, respectively. Meanwhile, in order to reduce dependence on equipment and to control volume flow, we have developed a straightforward microfluidic paper-based electrochemical device (µPEDs). The device enabled a continuous and sequential sample collection, achieving a sensitivity of 4,180 µA·mM·cm and a detection limit of 18 nM in artificial sweat within 2 s. Moreover, the electrode exhibited remarkable stability after 200 cycles, maintaining 98.5 % of its initial response. The flexibility test revealed an approximate 2 % rise in peak-to-peak distance following bending tests at a 5 mm radius of curvature. Thus, the approach and method presented in this paper carry substantial implications for the future development and application of wearable sweat sensors.