A stepping stone to enable preclinical evaluation of multimodal thin-film probes in small animal models

The successful translation of novel implantable technologies to clinical applications demands the comprehensive preclinical evaluation of the devices in vivo. This work aims to facilitate such translation by proposing a miniaturized multimodal thin-film deep brain stimulation ( $\mu$ DBS) device, tailored to rodent anatomy. The device was realized by incorporating glassy carbon (GC) electrodes into a thin-film polyimide-based substrate. The finished probe featured nine GC active sites with diameters ranging from $50\ \mu \mathrm{m}$ to $300\ \mu \mathrm{m}$ . The performed fast scan cyclic voltammetry revealed a dopamine sensitivity of $12.63 \pm 2.19\ \text{nA}\ \mu \mathrm{M}^{-1}, 20.72\pm 4.33\ \text{nA}\ \mu \mathrm{M}^{-1}, 135.44+8.24\ \text{nA} \mu \mathrm{M}^{-1}$ , and $68.50 \pm 3.42\ \mu \mathrm{M}^{-1}$ for electrodes with diameter of $50\ \mu \mathrm{m}, 100\ \mu \mathrm{m}, 200\ \mu \mathrm{m}$ , and $300\ \mu\mathrm{m}$ , respectively. The in vitro characterization assessed the $\mu\text{DBS}$ probe's ability to address electrical stimulation - in addition to neurochemical sensing - in a single integrated device. Future evaluation of the $\mu$ -DBS probes as a multimodal platform in animal models remains to be the next step in this path.