Probe for infrared neural stimulation
To reveal the underlying mechanism of deep tissue stimulation properly, we present the design, the fabrication scheme and functional testing of a novel, multimodal optrode for future INS experiments in vivo. Three modalities – electrophysiological recording, thermal measurement and delivery of infrared light – were integrated using silicon MEMS technology. Due to the monolithically integrated functionalities, a single probe is sufficient to determine safe stimulation parameters in vivo. As far as we know, this is the first planar, multimodal optrode designed for INS studies in the deep tissue.
Immuneresponse to nanostructured neural probes
In our study, bioactive properties of Si nanopillars compared to microstructured Si surfaces were investigated after being implanted for eight weeks, in vivo. To form the randomly nanostructured surfaces, we utilise black polycrystalline silicon (poly-Si) thin film. The advantage of black poly-Si is that its production can be integrated into the fabrication scheme of Michigan type silicon neural microelectrodes. Our results suggest that surface topography can alter the effect of implantation regarding the preservation of neurons in a distance of 0–50 μm from the track.
Polymer microECoG electrodes
Our surface electrodes have been efficiently used in animal studies on oscillatory connectivity and were also validated in pharmacological experiments. Our recent goal is to create novel, flexible, minimally invasive microsystems that are capable of high-resolution electrical monitoring of cortical activity and can be combined with other emerging neuroimaging techniques like functional magnetic resonance imaging, ultrafast ultrasound localization microscopy or two-photon microscopy.
Drug delivery microelectrodes
We have developed a silicon based miccroelectrode for simultaneous recording of cellular electrical activity and local drug delivery Fabrication scheme relies on the smart combination of Buried Channel Technology and Etching-Before-Grinding. Our micromachining concept provides injection, sampling and electrical recording — all integrated monolithically in a long and subsequently thinned silicon microelectrode. Feasibility of our microelectrode configuration has been demostrated in in vivo experiments using either external pressure (Pongrácz et al) or iontophoretic injection (Fekete et al).
Monitoring of brain temperature
In our work, we propose an implantable, calibrated multimodal biosensor that facilitates the complex investigation of thermal changes in both cortical and deep brain regions, which records multiunit activity of neuronal populations in mice. The fabricated neural probe contains four electrical recording sites and a platinum temperature sensor filament integrated on the same probe shaft within a distance of 30 µm from the closest recording site. The feasibility of the simultaneous functionality is presented in in vivo studies. The probe was tested in the thalamus of anesthetized mice while manipulating the core temperature of the animals.