The model for the coupons was designed in SolidWorks (Dassault Systèmes); refer to supplementary file 1. Coupons were 3D printed using a Prime 30 PolyJet 3D printer (Objet, Stratasys) using RGD720 photopolymer for the printing material (Stratasys). The coupon was printed at a resolution of 0.0008 inches. The coupon surface was sanded used P300 sandpaper to create a rougher surface for bacteria to attach.  Prior to inoculating, coupons were sterilized in 70% ethanol.