Double-Sided Sapphire Optrodes with Conductive Shielding Layers to Reduce Optogenetic Stimulation Artifacts

Abstract

Optrodes, which are single shaft neural probes integrated with microelectrodes and optical light sources, offer a remarkable opportunity to simultaneously record and modulate neural activities using light within an animal’s brain; however, a common problem with optrodes is that stimulation artifacts can be observed in the neural recordings of microelectrodes when the light source on the optrode is activated. These stimulation artifacts are undesirable contaminants, and they cause interpretation complexity when analyzing the recorded neural activities. In this paper, we tried to mitigate the effects of the stimulation artifacts by developing a low-noise, double-sided optrode integrated with multiple Electromagnetic Shielding (EMS) layers. The LED and microelectrodes were constructed separately on the top epitaxial and bottom substrate layers, and EMS layers were used to separate the microelectrodes and LED to reduce signal cross-talks. Compared with conventional single-sided designs, in which the LED and microelectrodes are constructed on the same side, our results indicate that double-sided optrodes can significantly reduce the presence of stimulation artifacts. In addition, the presence of stimulation artifacts can further be reduced by decreasing the voltage difference and increasing the rise/fall time of the driving LED pulsed voltage. With all these strategies, the presence of stimulation artifacts was significantly reduced by ~76%. As well as stimulation suppression, the sapphire substrate also provided strong mechanical stiffness and support to the optrodes, as well as improved electronic stability, thus making the double-sided sapphire optrodes highly suitable for optogenetic neuroscience research on animal models.

A 4-Channel Optogenetic Stimulation, 16-Channel Recording Neuromodulation System with Real-Time Micro-LED Detection Function

“…The optogenetic power density of a micro-LED is directly propotional to the driving current. At a current of 5 mA, the optogenetic power density can reach 1 mW/mm 2 [17,18], which meets the threshold requirement for the strong optical neurostimulation mentioned earlier. These microelectrodes are comparable in size to the neurons.…”

“…Figure 15b shows the input-referred noise performance of the circuit. The action potential is mainly distributed in the 100 Hz-7 KHz [17] frequency range, and the input integral noise within this bandwidth is 7.437 µVrms. The equivalent input-referred noise is mainly contributed by two input transistors, and this noise level could meet the requirement of a minimum SNR of 2 for a 50 µV neural signal.…”

“…The customized planar optrode for the neuromodulation system was designed (see Figure 2), which was based on a sapphire substrate and processes the characteristics of high stiffness, high transparency, and high optogenetic density [17,18]. The optrode has a total length of L = 13 mm, with an 8 mm segment specifically reserved for the insertion into rodent brain tissue.…”

An Integrated Neural Optrode with Modification of Polymer-Carbon Composite Films for Suppression of the Photoelectric Artifacts

“…In addition, we can further reduce the residual noise amplitude by adjusting the high and low pulse levels. ,, The experiment was carried out with the PEDOT:PSS-MWCNT and PEDOT-GO-modified microelectrode. As shown in Figure d–f about the test result of PEDOT:PSS-MWCNT microelectrode, when the low-level voltage is unchanged (0 V), the high-level voltage changes from 3 to 2.7 V, and the noise amplitude decreases from 1.80 to 0.93 mV by 48.33%, and when the high-level voltage is fixed at 2.7 V, the low-level voltage changes from 0 to 2.2 V (the value is lower than the μLED turn-on voltage), and the noise amplitude decreases to 0.57 mV by 38.71%.…”