Motivation
Multi-shank microelectrode arrays offer higher channel density and broader spatial coverage than single-shank designs — but they tend to fail faster. A leading reason is the mechanical trauma they cause during insertion: when four shanks enter the brain simultaneously, the cortex deforms significantly before penetration, straining tissue, disrupting vasculature, and triggering inflammatory responses that ultimately degrade the electrode-tissue interface. Reducing this insertion trauma without sacrificing the structural rigidity needed for unaided implantation is a core unsolved problem in neural interface engineering. Existing approaches — pneumatic inserters, vibration-assisted tools, surface coatings — all require additional surgical equipment or steps. A passive, fabrication-integrated solution would be far more practical.
Our Solution
Working with NeuroNexus, we developed and tested a custom four-shank MEA with staggered shank lengths and a non-uniform longitudinal thickness profile. The staggered geometry means each shank enters the brain sequentially rather than simultaneously, distributing mechanical load across time instead of applying it all at once. The non-uniform thickness — thinner at the recording tip, thicker proximally — preserves the mechanical rigidity needed to prevent buckling while reducing the cross-sectional area in contact with tissue. Finite element modeling confirmed that the critical buckling force exceeded the measured cortical penetration force by a factor of six or more across all shanks. We then validated the design in vivo in rat cortex, using a precision load cell to capture full force-displacement curves and quantify insertion energy — a metric we introduced as a more comprehensive measure of total mechanical trauma than peak force alone.
My Contributions
I ran all in-vivo insertion experiments. I operated a 20 g S-beam load cell force measurement system mounted to a NeuralGlider inserter, inserting probes at a controlled rate of 100 µm/s to a depth of 2 mm in rat motor cortex, and captured full force-displacement curves comparing the staggered-shank MEA against the conventional 4-shank design across five insertion trials per group. The data I collected showed the staggered design reduced total insertion energy by 57% (0.78 ± 0.12 vs. 1.8 ± 0.7 µJ, p=0.013) and peak cortical dimpling depth by 71% (190 ± 114 vs. 650 ± 183 µm, p=0.0014), with ~50% of staggered insertions producing zero detectable penetration force or dimpling. These findings were translated directly into NeuroNexus commercial probe design recommendations and published at IEEE NER 2026.
Project Outcomes
Looking to discuss further? Contact me at research@mkmaharana.com
Motivation
For a neural implant to be clinically useful, it has to work not just on day one — it has to maintain reliable electrical contact with neurons for months or years. A central challenge is the electrode coating: the material that sits at the interface between the device and the brain, transducing ionic neural signals into electronic measurements. Iridium oxide coatings like SIROF are effective and well-characterized, but iridium is expensive and increasingly limited in supply. Ruthenium oxide is a lower-cost alternative with similar electrochemical properties in acute settings — but its long-term stability in the living brain hadn't been rigorously tested. Without that data, it couldn't be seriously considered for chronic implants. We needed to know whether RuOx could maintain stable impedance, charge storage, and recording quality over a clinically relevant timescale.
Our Solution
We implanted RuOx-coated amorphous silicon carbide (a-SiC) microelectrode arrays in rat motor cortex and tracked their performance weekly for 16 weeks. Each week we measured electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) in vivo to assess impedance at clinically relevant frequencies and charge storage capacity at two sweep rates, then immediately followed with neural recordings to quantify active electrode yield, signal amplitude, and signal-to-noise ratio. By pairing electrochemical and electrophysiological measures at every timepoint, we could distinguish true electrode degradation from recording variability — and track both independently across the full implantation period.
My Contributions
I led the data collection of this study. Performing all baseline in-vitro electrochemical characterization before implant, then executed weekly in-vivo EIS and CV sessions using a Gamry potentiostat across the full 16-week implantation period — tracking charge storage capacity at 50 mV/s and 50,000 mV/s sweep rates and 1 kHz impedance at every timepoint. I collected weekly neural recordings and quantified active electrode yield (AEY%), peak-to-peak voltage (Vpp), and SNR across all animals. Results confirmed stable electrochemical performance through week 16, with AEY sustained between 40–80% and stable Vpp (~70–170 µV, p=0.17 for trend). I independently designed and presented the scientific poster as first author at the UT Dallas Undergraduate Research Scholar Award (URSA) Semifinals (2025).
Project Outcomes
Poster: URSA 25 Poster
Looking to discuss further? Contact me at research@mkmaharana.com
