Highly Sensitive Flexible Electrochemical pH Sensor with Laser Photothermally Generated Porous Graphene

Stephen Buchanan(1), Shirin Movaghgharnezhad(1), Erin Van Dell(1), Morgan Collins(1), Pilgyu Kang(1,2) (1) Department of Mechanical Engineering, George Mason University, 4400 University Drive, Fairfax, VA, 22030 (2) Department of Bioengineering, George Mason University, 4400 University Drive, Fairfax, VA, 22030

Laser-induced graphene (LIG) has previously demonstrated itself as an ideal material for wearable pH sensors within the field of biosensing and harsh-environment monitoring due to its unique properties including high electrical conductivity, high electron mobility, large surface area, and its three-dimensional (3D) morphology. However, studies on LIG-based pH sensing have been focused on the performance of such sensors synthesized on polyimide (PI) film. In this study, we use highly fluorinated colorless polyimide (cPI) film to synthesize 3D porous graphene for the development of flexible pH sensors with an enhanced sensitivity. 3D porous graphene is photothermally engraved on cPI film by using a pulsed infrared CO2 laser (λ = 10.6 μm) at ambient conditions. The additional fluorine atoms in cPI film form gaseous products that are discharged during laser-based graphitization, allowing for the generation of abundant nanopores with diameters less than 2 nm. The cPI-LIG electrode reveals increased specific surface area in relation to an enhanced number of pores, leading to higher electrolyte accessibility and more electrolyte penetration during electrochemical characterization, respectively. We fabricated cPI-LIG devices comprising of reference, working, and counter electrodes using a synchronous laser nanomanufacturing approach. Subsequently, highly microporous graphene with 3D morphology is functionalized by polyaniline (PANI) to achieve a high pH-sensitive conductive electrode used for potentiometric-based electrochemical sensing. We conducted potentiometric measurements in different buffer solutions ranging from pH 4-7 in order to evaluate the performance of the pH sensors. Lastly, the potential of high flexibility characteristics in the devices was studied under bending and twisting tests of up to 10000 cycles. Our results demonstrate a superior potentiometric response of cPI-LIG electrode with enhanced sensitivity in the linear range of pH 4-7 than that of PI-LIG based pH sensor, indicating the potential of the cPI-LIG device for wearable biosensing applications and flexible harsh-environment monitoring systems.

Additional Abstract Information

Presenter: Stephen Buchanan

Institution: George Mason University

Type: Poster

Subject: Engineering

Status: Approved

Time and Location

Session: Poster 6
Date/Time: Tue 2:00pm-3:00pm
Session Number: 4627