Hybrid intracerebral probe with integrated bare LED chips for optogenetic studies

Ayub, Suleman; Gentet, Luc J.; Fiáth, Richárd; Schwaerzle, Michael; Borel, Mélodie; David, François; Barthó, Péter; Ulbert, István; Oliver, Paul; Ruther, Patrick

doi:10.1007/s10544-017-0190-3

Cited by 35 publications

(36 citation statements)

References 29 publications

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“…Further developments to our probe could include monolithically manufacture LEDs onto the probe, as demonstrated by other studies [ 5 , 40 ], ultimately leading to probe cross-section reduction. An interesting approach to address high-footprint commercial LED chips is reported by Ayub et al [ 41 ]. In that study, LED chips are mounted on a thin polyimide-based substrate, stiffened using a micromachined ladder-like silicon structure.…”

Section: Resultsmentioning

confidence: 99%

LED Optrode with Integrated Temperature Sensing for Optogenetics

et al. 2018

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In optogenetic studies, the brain is exposed to high-power light sources and inadequate power density or exposure time can cause cell damage from overheating (typically temperature increasing of 2 ∘C). In order to overcome overheating issues in optogenetics, this paper presents a neural tool capable of assessing tissue temperature over time, combined with the capability of electrical recording and optical stimulation. A silicon-based 8 mm long probe was manufactured to reach deep neural structures. The final proof-of-concept device comprises a double-sided function: on one side, an optrode with LED-based stimulation and platinum (Pt) recording points; and, on the opposite side, a Pt-based thin-film thermoresistance (RTD) for temperature assessing in the photostimulation site surroundings. Pt thin-films for tissue interface were chosen due to its biocompatibility and thermal linearity. A single-shaft probe is demonstrated for integration in a 3D probe array. A 3D probe array will reduce the distance between the thermal sensor and the heating source. Results show good recording and optical features, with average impedance magnitude of 371 kΩ, at 1 kHz, and optical power of 1.2 mW·mm−2 (at 470 nm), respectively. The manufactured RTD showed resolution of 0.2 ∘C at 37 ∘C (normal body temperature). Overall, the results show a device capable of meeting the requirements of a neural interface for recording/stimulating of neural activity and monitoring temperature profile of the photostimulation site surroundings, which suggests a promising tool for neuroscience research filed.

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Section: Resultsmentioning

confidence: 99%

LED Optrode with Integrated Temperature Sensing for Optogenetics

et al. 2018

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“…A long neural probe is shown in Figure B, where the shank is made from hollow parylene tube . An acute optical probe bonded to a printed circuit board (PCB) and connected to a flexible platinum cable, which is inserted into a mini zero‐insertion‐force socket (mini‐ZIF), is shown in Figure C …”

Section: Biocompatibilitymentioning

confidence: 99%

Section: Biocompatibilitymentioning

confidence: 99%

“…The µLEDs are typically flip chip bonded to the underlying substrate, which is produced using standard photolithographic techniques. Several devices with tip‐mounted µLEDs and multiple electrode recording sites have been developed on substrates including polyimide, SU‐8, or polycrystalline diamond . µLED devices capable of generating above threshold stimulation for optogenetic applications can consume around 17 mW per channel, which is almost 20 times higher per channel than a 100 channel electrical device …”

Section: Feasibilitymentioning

confidence: 99%

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Biological Considerations of Optical Interfaces for Neuromodulation

Hart

Kameneva

Wise

et al. 2019

Advanced Optical Materials

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“…A more promising approach is based on the integration of LEDs either as bare LED chips ( Kwon et al, 2013a ; Ayub et al, 2017 ; Ji et al, 2017 ) or as thin-film μLEDs ( Goßler et al, 2014 ; Hahn et al, 2014 ; Wu et al, 2015 ; Ayub et al, 2016 ; Klein et al, 2016 ; Scharf et al, 2016 ) on the implantable probe. In the case of bare LED chips, the probe design needs to fit to the size of available chips with typical lateral dimensions of 220 × 270 μm 2 and a thickness of 50 μm or more ( Schwaerzle et al, 2016 ).…”

Section: Introductionmentioning

confidence: 99%

High-Density μLED-Based Optical Cochlear Implant With Improved Thermomechanical Behavior

et al. 2018

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This study reports the realization of an optical cochlear implant (oCI) with optimized thermomechanical properties for optogenetic experiments. The oCI probe comprises 144 miniaturized light-emitting diodes (μLEDs) distributed along a bendable, 1.5-cm-long, 350-μm-wide and 26-μm-thick probe shaft, individually controlled via a n × p matrix interconnection. In contrast to our earlier approach based on polyimide (PI) and epoxy resin with different thermal expansion coefficients, the μLEDs and interconnecting wires are now embedded into a triple-layer stack of a single, biocompatible, and highly transparent epoxy material. The new material combination results in a pronounced reduction of thermomechanical bending in comparison with the material pair of the earlier approach. We developed a spin-coating process enabling epoxy resin layers down to 5 μm at thickness variations of less than 7% across the entire carrier wafer. We observed that the cross-linking of epoxy resin layers strongly depends on the spin-coating parameters which were found to be correlated to a potential separation of epoxy resin components of different densities. Furthermore, various metallization layers and corresponding adhesion promoting layers were investigated. We identified the combination of silicon carbide with a titanium-based metallization to provide the highest peeling strength, achieving an adhesion to epoxy improved by a factor of two. In order to obtain a high process yield, we established a stress-free implant release using the electrochemical dissolution of a sacrificial aluminum layer. The direct comparison of oCI probe variants using a single epoxy material and the combination of PI and epoxy resin revealed that the epoxy-resin-only probe shows minimal thermomechanical probe bending with a negligible hysteresis. The thermal probe characterization demonstrated that the temperature increase is limited to 1 K at μLED DC currents of up to 10 mA depending on the stimulation duration and the medium surrounding the probe. The optical output power and peak wavelengths of the new oCI variant were extracted to be 0.82 mW and 462 nm when operating the μLEDs at 10 mA, 10 kHz, and a duty cycle of 10%. The optical power corresponds to a radiant emittance of 407 mW/mm2, sufficient for optogenetic experiments using channelrhodopsin-2.

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Hybrid intracerebral probe with integrated bare LED chips for optogenetic studies

Cited by 35 publications

References 29 publications

LED Optrode with Integrated Temperature Sensing for Optogenetics

LED Optrode with Integrated Temperature Sensing for Optogenetics

Biological Considerations of Optical Interfaces for Neuromodulation

High-Density μLED-Based Optical Cochlear Implant With Improved Thermomechanical Behavior

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