Electrodes were assembled into microneedle devices using 3x1 arrays of 600-micron tall silicon microneedles (Nanopass Technologies, Ness Ziona, Israel) that are FDA approved for human use with their existing indication being for injection of drugs into the skin. First, we laser cut adhesive spacers (Universal Laser Systems, Scottsdale, AZ) from double-sided, 90 µm thick microfluidic tape (9965, 3M, Saint Paul, MN) to attach the microneedles to the aptamer sensor substrate and to define the volume of the sensing cavity (Figure ). Prior to attaching the microneedles onto the sensor substrates, we coated the sensor electrodes with 10% w/w trehalose solution and dried them under vacuum. Then, we added auto-clave sterilized microneedle substrate onto the adhesive spacer window. For thin-film electrodes polyimide tape was used to electrically insulate any exposed gold. At this point these devices may be shelf-stored in a dry, nitrogen environment for 90 days or more. Prior to human subject testing the microneedles and sensing cavity were wetted with sterile PBS solution by placing the sensors under -25 inHg vacuum for 15 min and then submerging them in PBS while still under vacuum. The vacuum was then released to fill the sensors and microneedles. All devices were tested immediately after filling. CAD files with dimensions for the parts described below are included in the online supplemental files.