Wettability Patterning of Flexible Laser Induced Graphene Electrodes for Robust Multiplexed Electrochemical Ion Sensing in the Wearable Health and Environmental Monitoring Domains

Description:
Solid contact electrodes are prone to selectivity, stability, and drift issues due in part to the water layer that can build-up between the polymeric sensing layer and the electrode interface during ion sensing in aqueous solutions. Here we demonstrate that such a water layer can be significantly reduced by converting typically hydrophilic LIG into LIG that is near superhydrophobic (static water contact angle of ∼143°). This tuning of the surface wettability is controlled via a facile double lasing process under low laser fluence settings that can be performed in ambient conditions. The LIG is direct write synthesized and patterned on polyimide substrates to form graphene-based electrochemical electrodes without the need for ink information, printing, and post-print annealing that is necessary with conventional printed graphene circuits. Moreover, the LIG exhibits an inherent 3D porous morphology that significantly increases the electrode electroactive surface and consequent sensor sensitivity over traditional 2D planar graphene electrodes. Next, we demonstrate how the ISE can be functionalized with PVC-based ion selective membranes containing ionophores for potassium, nitrate, ammonium, sodium, and hydrogen (pH) ion sensing in various biological solutions including sweat during wearable health monitoring, urine in patient hydration studies, and soil and water for nutrient/fertilizer monitoring in farm fields. Such ion sensors displayed near-Nernstian sensitivities and wide sensing ranges over four orders of magnitude (10^–6 M to 10^–2 M concentration range). The near superhydrophobic LIG electrodes have permitted us to achieve sensor stability for over 4 months of continual use. We also demonstrate how hydrophilic LIG tracks surrounded by near superhydrophic sidewalls can be used for open microfluidic fluid transport for multiplexed ion sensing and that hydrophilic LIG is well suited for enzymatic pesticide sensing and Salmonella immunosensing.

Speaker: Jonathan Claussen - Iowa State University
Prof. Jonathan Claussen is currently an Associate Professor in the Department of Mechanical Engineering at Iowa State University. He has published over 60 peer-reviewed journal articles, 5 book chapters, 7 issued patents, and 5 pending patents in his field and he currently serves as an Associate and Academic Editor of Microchimica Acta and PLOS One respectively. Prof. Claussen’s research interests focus on the fabrication of nanomaterials and nanostructured devices for a wide variety of applications including biosensors, energy harvesters, and cellular interface materials. His laboratory specializes in developing flexible and disposable graphene-based biosensors developed from inkjet and aerosol printing as well as through laser writing. Such technology has been used in a range of applications including for in-field or point-of-service monitoring of pesticides, fertilizers, cancer biomarkers, foodborne pathogens, and electrolytes.