Ultracompliant Hydrogel‐Based Neural Interfaces Fabricated by Aqueous‐Phase Microtransfer Printing

Abstract

Hydrogel-based electronics are ideally suited for neural interfaces because they exhibit ultracompliant mechanical properties that match that of excitable tissue in the brain and peripheral nerve. Hydrogel-based multielectrode arrays (MEA) can conformably interface with tissues to minimize inflammation and improve the reliability to enhance signal transduction.However, MEA substrates composed of swollen hydrogels exhibit low toughness and low adhesion stability when laminated on the tissue surface and also present technical challenges for processes commonly employed in MEA fabrication. Here, we describe a new strategy to fabricate ultracompliant MEA based on aqueous-phase transfer printing. This technique employs redox active adhesive motifs in hygroscopic polymer precursors that simultaneously form hydrogels through sol-gel phase transitions and bond to underlying microelectronic structures. Specifically, in situ gelation of 4-arm-polyethylene glycol-grafted catechol [PEG-Dopa]4 hydrogels induced by oxidation using Fe 3+ produces conformal adhesive contact with the underlying MEA, robust adhesion to electronic structures, and rapid dissolution of watersoluble sacrificial release layers. MEA are then integrated on hydrogel-based substrates to produce free standing ultracompliant neural probes, which are then laminated to the surface of the dorsal root ganglia in feline subjects to record single-unit neural activity.

High-density Neural Recordings from Feline Sacral Dorsal Root Ganglia with Thin-film Array

“…While the types of units recorded from sacral DRG in some of these studies were similar (cutaneous, bladder-related, pudendal-stimulation driven), there was no evidence of unit oversampling on neighboring sites. Higher density recordings have been made from the surface of DRG, down to 25 µm electrode site pitch, [19]- [22], but despite the potential advantages of non-penetrating arrays these were fundamentally limited to recording single-unit activity from the shallowest ~150 µm of the DRG [19]. Slightly higherdensity recordings have been reported in the peripheral nervous system.…”

Advances in Materials and Structures for Ingestible Electromechanical Medical Devices

“…Tr ansfer printing is ascalable approach to the manufacturing of flexible electronic devices for many applications including ingestible electromechanical systems.O rganic semiconductors can be deposited on tattoo-paper and transfer printed to various substrates including foods and capsules ( Figure 5). [46,47] Novel materials and companion fabrication techniques could preserve device integrity as biodegradable devices begin to disintegrate within the GI tract upon hydration. Transfer printing is also amenable for integrating silicon-based electronics with flexible substrates including those used as ingestible capsules.…”

“…[44,45] Tr ansfer printing to hygroscopic substrates such as hydrogels has also recently been demonstrated by using bioinspired adhesives. [46,47] Novel materials and companion fabrication techniques could preserve device integrity as biodegradable devices begin to disintegrate within the GI tract upon hydration. Chemie…”

Materialien und Strukturen für schluckbare elektromechanische medizinische Funktionseinheiten

“…Verzehrbare Kapseln haben kleine Volumina (< 2cm 3 ), kurvenfçrmige Geometrien und werden oft aus weichen Materialien wie Gelatine hergestellt. [46,47] Neuartige Materialien und damit einhergehende Fertigungstechniken kçnnten die Integritätv on Funktionseinheiten aufrechterhalten, da sich biologisch abbaubare Funktionseinheiten bei Hydratation im Magen-Darm-Trakt zu zersetzen beginnen. Organische Halbleiter kçnnen auf Tattoo-Transferpapier aufgebracht und im Transferdruck auf verschiedene Substrate,e inschließlich Lebensmittel und Kapseln übertragen werden (Abbildung 5).…”

“…[44,45] Transferdruck auf hygroskopische Substrate wie Hydrogele wurde kürzlich ebenfalls demonstriert, unter Verwendung biologisch inspirierter Adhäsive. [46,47]…”