Localized therapy of the highly malignant brain tumor glioblastoma multiforme (GBM) could help to drastically improve the treatment efficiency and increase the patient's median survival. Here, a macroscopic PDMS matrix composed of interconnected microchannels for tailored drug release and localized GBM therapy is introduced. Based on a simple bottomup fabrication method using a highly versatile sacrificial template, the presented strategy solves the scaling problem associated with the previously developed microchannel-based drug delivery systems, which were limited to two dimensions due to the commonly employed top-down microfabrication methods. Additionally, tailoring of the microchannel density, the fraction of drug-releasing microchannels and the macroscopic size of the drug delivery systems enabled precise adjustment of the drug release kinetics for more than 10 days. As demonstrated in a long-term GBM in vitro model, the release kinetics of the exemplarily chosen GBM drug AT101 could be tailored by variation of the microchannel density and the initial drug concentration, leading to diffusion-controlled AT101 release. Adapting a previously developed GBM treatment plan based on a sequential stimulation with AT101, measured anti-tumorigenic effects of free versus PDMS-released AT101 were comparable in human GBM cells and demonstrated efficient biological activity of PDMS-released AT101.

Conductive serpentine interconnects comprise fundamental building blocks (e.g., electrodes, antennas, wires) of many stretchable electronic systems. Here we present the first numerical and experimental studies of freestanding thin-film TiNiCuCo superelastic alloys for stretchable interconnects. The electrical resistivity of the austenite phase of a Ti53.3Ni30.9Cu12.9Co2.9 thin-film at room temperature was measured to be 5.43×10-7 Ω m, which is larger than reported measurements for copper thin-films (1.87×10-8 Ω m). Structuring the superelastic conductor to limit localized strain using a serpentine geometry led to freestanding interconnects that could reach maximum serpentine elongations of up to 153%. Finite element analysis (FEA) simulations predicted that superelastic serpentine interconnects can achieve significantly larger (~5X–7X) elastic elongations than copper for the same serpentine geometry. FEA predictions for stress distribution along the TiNiCuCo serpentine interconnect were experimentally verified by infrared imaging and tensile testing experiments. The superior mechanical advantages of TiNiCuCo were paired with the high electronic conductivity of copper, to create Cu/TiNiCuCo/Cu serpentine composites that were demonstrated to serve as freestanding electrical interconnects between two LEDs. The results presented in this manuscript demonstrate that thin-film superelastic alloys are a promising material class to improve the performance of conductors in stretchable and flexible electronics.

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