Printed graphene (PG) and laser induced graphene (LIG) have recently shown promise in the fabrication of low-cost, flexible electrical circuits. However, biosensing applications involving PG and LIG have been constrained due in part to low resolution printing, destructive post-print annealing steps, low electrochemical reactivity, and relatively smooth, planar non-electroactive surfaces.  In this presentation, we demonstrate how low-cost printed and flexible graphene circuits can be tailored for use in a wide range of applications including electrochemical biosensing, stem cell differentiation, and open microfluidic devices. First, we demonstrate how the utility of PG is expanded through high-resolution patterning, post-print laser annealing, and biorecognition agent functionalization techniques. A new graphene patterning technique [i.e., inkjet maskless lithography (IML)] that is used to form high resolution, flexible graphene films (line widths down to 20 µm) that significantly exceeds current graphene inkjet printing resolution (line widths ~ 60 µm). Next, a rapid pulse laser annealing technique with a Nd:YAG laser or CO<sub>2</sub> laser is used to tune the electrical conductivity, surface wettability, surface roughness, and electrochemical reactivity of the IML PG as well as to make LIG.  Finally, we demonstrate how these PG and LIG electrodes can be biofunctionalized with enzymes, ionphore membranes, and antibodies for pesticide and nitrogen sensing in soil as well as bacteria detection within food broth solutions. The detection limits of the biosensors so far have achieved approximately 0.6 nM for organophosphate pesticides and 20 mM for ammonium and nitrate ions which well below the concentration limits we would expect for drinking water or soil samples. Such sensing results demonstrate that PG and LIG technology is well-suited for in-field, low-cost biosensing. Finally, we demonstrate how the hydrophobicity of the PG can be tuned from hydrophilic to superhydrophobic to help drive fluid on the surface <i>via </i>Laplace pressure. Such an open microfluidic paradigm could be useful for a variety of applications including agricultural-based biosensing.

Printed and laser induced graphene electrochemical sensors for in-field pesticide and fertilizer ion monitoring

2019 Fall National Meeting

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