Electromicrofluidic Device on Multilayered Laser-Induced Polyamide Substrate for Diverse Electrochemical Applications

Microfluidic devices with integrated electrodes, called electromicrofluidic (EMF) device, have been reported for multiple applications. In this work, a unique approach to realizing a multilayered EMF device, with microchannel and integrated electrodes on the same polyamide (PI) substrate, has been presented. A computer-controlled CO 2 laser ablation method, with varying speeds and power values, was employed to form laser-induced graphene (LIG) on a PI substrate as per the desired design. Initially, to create a microchannel layer, the formed LIG was peeled off which left behind an etched pattern. Subsequently, to realize an electrode layer, the PI substrate with microchannel was further ablated to create patterned LIG. An optimal flow rate of 100~\mu \text{L} /min via a controlled syringe pump was established in EMF device. As a prototype, the developed platform, with microchannel and electrodes, was explored for variable electrochemical applications. First, the electrochemical sensing of uric acid displayed a limit of detection (LOD) as 0.61~\mu \text{M} in a linear range from 10~\mu \text{M} to 3 mM with significant recovery values. Furthermore, the polarization performance for fuel cell application was evaluated on the developed EMF platform using the chronoamperometry (CA) method with a stable open-circuit potential (OCP), harnessing the maximum power density obtained was 3.027 nW/cm 2 . Finally, an array of interdigitated microelectrodes (IDEs) was realized to examine impedance-based nitrite detection. Overall, the presented multilayered EMF devices with microchannel and electrodes on the single sheet authenticate the applicability of the designed platform for a variety of sensing and energy harvesting applications.