(a) Illustration and image of an 8-graphene-electrode/FET array with a microfluidic channel on top. This entire device sits on a printed circuit board. (b) Cross-sectional illustration of an individual graphene site. (c) Optical micrograph of a portion of a fabricated graphene array. For an individual graphene site, W=90 μm and L=45 μm (scale bar, 120 μm). (d) Raman spectrum of a graphene sample transferred onto a SiO2/Si substrate and integrated graphene Raman two-dimensional (2D) peak intensity map from 2,600 cm−1 to 2,800 cm−1 (scale bar, 1 μm).