The electronics modules were manufactured using industry standard printed circuit board (PCB) fabrication and surface-mount assembly methods, and consisted of a single ca. 5 mm × 12 mm PCB containing all electronic components including the thermistor temperature sensor and a separate battery pack containing two 1.55V SR416 silver oxide batteries (Fig 1). Electronic components were purchased from Digikey (Thief River Falls, MN, USA). The PCBs were fabricated by Sunstone Circuits (Mulino, OR, USA) and board assembly was completed by Screaming Circuits (Canby, OR, USA). Silicone IVRs with an open cavity for the electronics module were fabricated by injection molding from liquid silicone resin (MED-4840 LSR, Nusil, Carpenteria, CA, USA) using a custom single cavity mold and a laboratory-scale injection molding machine designed and constructed in-house . Assembled electronics modules were sealed in the IVR using a silicone adhesive (MED3-4213, Nusil, Carpenteria, CA, USA) so that the electronics module and battery are completely encased in silicone and with no contact with vaginal fluid.