Fig. 4: Implantation and Immune Response of Utah-like Electrodes.

a Semi-flexible Utah-like Electrode with PI-based SU-8 Microneedles. (i) Photograph of the Utah-like Electrodes⁴⁵; b High-throughput Semi-flexible Utah-like Electrode with PI-based Silicon Microneedles⁴⁶. (i) Photograph of a 1024-channel, 32-channel silicon microneedle electrode and image of it implanted on the brain surface; (ii) Coronal tissue sections 73 days post-implantation, showing two-photon imaging and fluorescence microscopy photos; cell nuclei (DAPI, blue), neurons (NeuN antibody, green), astrocytes (GFAP antibody, red), and microglia (Iba1 antibody, magenta). The red arrow indicates tissue penetration by a single probe, and the yellow dashed box highlights the enlarged area on the right. c Microfluidic semi-flexible Utah-like electrodes⁴⁷. (i) Images showing the electrode and cross-sectional view of the arched microfluidic channel; (ii) The microfluidic channel shown empty (left) and filled with stained water (right); (iii) SEM image of the electrode, featuring a pitted structure. The channel width is approximately 200 µm, and the height is 40 µm. Scale bar: 500 µm; (iv) Fluorescence image of rat brain slices containing the electrode implantation site. DAPI and Dextran Texas Red were used to label cell nuclei and visualize the delivery area, respectively. At the bottom, a magnified image of the region around the electrode. The white dashed line indicates the electrode trajectory. Scale bar: 500 µm. d Fully Flexible Origami Electrode⁴⁹. (i) Full-view photograph of the electrode. At the top, a rotational view (top right) of the 3D neural mapping device of the Fully Flexible Origami Electrode, consisting of 9 ECoG electrodes and 4 probes, with each probe containing 6 electrodes. The recording area of each electrode is 20 × 20 µm², with a 500 µm spacing between the ECoG electrodes and a 200 µm spacing between the probe electrodes. Each probe has a height of approximately 1.5 mm and a thickness of <20 µm, including both sides of the folded flexible substrate. Scale bar, 250 µm. On the bottom left, the Fully Flexible Origami Electrode is wrapped around a glass rod with a radius of 5 mm. Scale bar, 500 μm. On the bottom right, a photo of the PEG-coated 3D neural mapping device vertically inserted into the anterior part of the mouse brain, with part of it inserted perpendicularly into the brain. Scale bar, 250 μm; (ii) Immune response around the implanted electrode, showing neurons; fluorescence images of activated astrocytes (GFAP, green fluorescence) and microglia (IBA1, red fluorescence) in the tissue surrounding the electrode array, and an expanded image (yellow box). (White arrow: electrode implantation site, white dotted line: electrode position). Reproduced with permission⁴⁵. Copyright 2016, Zhuolin, X., Jingquan, L., Chengkuo, L., et al. Reproduced with permission⁴⁶. Copyright 2022, Wiley‐VCH GmbH. Reproduced under terms of the CC-BY license⁴⁷. Copyright 2021, Yoo Na, K., Namsun, C., Jae-Won, J., et al. Reproduced under terms of the CC-BY license⁴⁹. Copyright 2022, Ju Young, L., Sang Hoon, P., Yujin, K., et al.