Electrical Performance of Representative DDFTTF-Based Transistors Fabricated on PLGA Substrates. Transistors fabricated from thermally evaporated DDFTTF semiconducting layers exhibited relatively high mobilities and on-off ratios on both (a) nPVA and (b) xPVA dielectrics. The device performance metrics for the device depicted in (a) are μ = 0.153 cm²-sec-^-1-V^-1, I_on/I_off = 3.49 × 10³, and V_T = -15.6 V. The device performance metrics for the device depicted in (b) are μ = 0.060 cm²-sec-^-1-V^-1, I_on/I_off = 2.93 × 10³, and V_T = -13.6 V.

In Vitro Degradation of Devices. a) A plot of mass remaining and water uptake by mass (hydration) demonstrates that devices fabricated on PLGA substrates were initially resistant to mass degradation and water uptake. However, after 30 days, significant mass loss and water uptake was initiated. Near total mass loss and 100% device hydration was observed at 70 days. b) Photographs from representative devices at various stages of the degradation time line suggest that device integrity was intact up until 40 days with near total device resorption at 70 days. Devices also transitioned from being initially optically transparent (0 days) to opaque within 10 day. Scale bar represents 5 mm for all panels.

Materials Selection and Device Configuration of Organic Thin Film Transistors. (a) The chemical structures of the semiconductor (DDFTTF), the dielectric (PVA), and the substrate (PLGA) are shown. (b) These materials are processed into devices in top-contact configuration as shown. Briefly, PLGA was melt-processed into substrates approximately 1 × 1 cm² in area and 2 mm in thickness. Silver gate contacts were evaporated through a shadow mask. PVA dielectrics were spin coated from solution followed by thermal evaporation of DDFTTF semiconducting layers and gold source-drain contacts. The final device geometry contained channel lengths of 50 μm and a W/L ratio of 20.

Effect of Aqueous Exposure to Device Performance. The kinetics of electrical performance as a function of cumulative time exposed to ddH₂O is shown for a set of 20 devices. Effective mobility (μ_,eff) was measured to decrease gradually over the course of 6 hr. I_on/I_off was immediately reduced upon exposure to liquid water and then very gradually decreased over the remainder of the time course.