Direct laser writing of 3D electrodes on flexible substrates

Brown, M. C.; Zappitelli, Kara M.; Singh, Loveprit; Yuan, Rachel C.; Bemrose, Melissa A.; Brogden, Valerie; Miller, David J.; Smear, Matthew C.; Cogan, Stuart F.; Gardner, Timothy J.

doi:10.1038/s41467-023-39152-7

Cited by 24 publications

(18 citation statements)

References 51 publications

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“…1b), with a strong emphasis on biocompatibility and mechanical exibility. We encase gold wiring in a polyimide lm about 4 µm thick, taking advantage of polyimide's proven MEMS process stability and biocompatibility 42,43 . The multistep fabrication sequence includes metal desposition, polyimide solidi cation, gold evaporation, and another polyimide layer, followed by Reactive Ion Etching (RIE) device etching to expose the recording sites, bonding pads, and vias.…”

Section: Resultsmentioning

confidence: 99%

Through-Polymer Via Technology-Enabled Flexible, Lightweight, and Integrated Device for Implantable Neural Probes

Sun,

Zhou,

Tian

et al. 2024

Preprint

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In implantable electrophysiological recording systems, the headstage typically consists of neural probes interfacing with brain tissue and integrated circuit chips for signal processing. Although advancements in MEMS and CMOS technology have significantly improved these components, their connection still relies heavily on conventional printed circuit boards and sophisticated adapters. This traditional approach adds considerable weight and volume, especially as channel counts increase. To address this, we have developed a Through-Polymer Via (TPV) method, inspired by the Through-Silicon Via (TSV) technique in advanced three-dimensional packaging. This innovation enables the vertical integration of flexible probes, amplifier chips, and PCBs, culminating in the creation of a Flexible, Lightweight, and Integrated Device (FLID). The total weight of FLID is only 25% of that of conventional counterparts using adapters, which significantly enhances animal activity levels, nearly matching those of control animals without implants. Furthermore, by incorporating a platinum-iridium alloy as the top layer material for electrical contacts, the FLID demonstrates exceptional electrical performance, enabling in vivo measurements of both local field potentials and individual neuron action potentials. Our findings not only showcase the potential of the FLID in scaling up implantable neural recording systems but also mark a significant step forward in the field of neurotechnology.

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Section: Resultsmentioning

confidence: 99%

Through-Polymer Via Technology-Enabled Flexible, Lightweight, and Integrated Device for Implantable Neural Probes

Sun,

Zhou,

Tian

et al. 2024

Preprint

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“…Such process was demonstrated for 100 µm pixels, but it is difficult to scale it down to much smaller pixel pitch, such as 20 µm. Another approach could be based on 3D polymer structures, which can be formed by 2photon laser lithography and subsequently metalized for conduction [30][31][32]. However, polymer features (pillars or walls) of high aspect ratio tend to deform over time, leading to cracking of the metal coating.…”

Section: Discussionmentioning

confidence: 99%

Three-dimensional electro-neural interfaces electroplated on subretinal prostheses

Butt,

Wang,

Shin

et al. 2024

J. Neural Eng.

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Objective. High-resolution retinal prosthetics offer partial sight restoration to patients blinded by retinal degenerative diseases through electrical stimulation of remaining neurons. Decreasing pixel size enables increasing prosthetic visual acuity, as demonstrated in animal models of retinal degeneration. However, scaling down the size of planar pixels is limited by the reduced penetration depth of the electric field in tissue. We investigated 3-dimensional structures on top of photovoltaic arrays for enhanced penetration of the electric field, permitting higher resolution implants.Approach. 3D COMSOL models of subretinal photovoltaic arrays were developed to accurately quantify the electrodynamics during stimulation and verified through comparison to flat photovoltaic arrays. Models were applied to optimize the design of 3D electrode structures (pillars and honeycombs). Return electrodes on honeycomb walls vertically align the electric field with bipolar cells for optimal stimulation. Pillars elevate the active electrode improving proximity to target neurons. The optimized 3D structures were electroplated onto existing flat subretinal prostheses based on modelling results.Main results. Simulations demonstrate that despite exposed conductive sidewalls, charge mostly flows via high-capacitance sputtered Iridium Oxide films topping the 3D structures. The 24 µm height of honeycomb structures was optimized for integration with the inner nuclear layers cells in the rat retina, whilst 35 µm tall pillars were optimized for penetrating the debris layer in human patients. Implantation of released 3D arrays demonstrates mechanical robustness with histology demonstrating successful integration of 3D structures with the rat retina in-vivo.Significance. Electroplated 3D honeycomb structures produce vertically oriented electric fields, providing low stimulation thresholds, high spatial resolution, and contrast for pixel sizes down to 20 µm. Pillar electrodes offer alternatives for extending past debris layers. Electroplating of 3D structures is compatible with the fabrication process of flat photovoltaic arrays, enabling much more efficient stimulation.

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“…Laser technology is widely used in the field of flexible material manufacturing and can be used for the fabrication of bio-sensors, soft electronic devices and e-skin. [98][99][100][101][102][103] In a recent study, three-dimensional integrated electronic devices made of elastomers were reported, where laser ablation and controlled soldering were used to create vertical interconnect accesses (VIA). The pattern designs of the electrodes, heaters, and VIA connectors were all fabricated using the laser ablation technique (Fig.…”

Section: Human-machine Interface Based On Soft E-skinmentioning

confidence: 99%