Fig. 1: An overview of the uFINE-I and intravascular implantation system.

a DSA images of the sheep intracranial venous system, showing the confluence of sinuses and its connecting venous branches from different angles. These structures include the dorsal cerebral vein (DCV), dorsal sagittal sinus (DSS), sigmoid sinus (SiS), temporal sinus (TeS), transverse sinus (TrS), and the second emissary vein of the retroarticular foramen (EVRF-2). A: anterior, P: posterior, R: right, L: left, S: superior, I: inferior. Scale bars, 10 mm. b Schematic diagram showing the dorsal view of the relative position between the sheep venous system and the brain tissue. The left ellipse represents the target zone around the confluence of sinuses for the implantation system, and the right ellipse shows the uFINE-I probe in the brain tissue after penetration, surrounded by neurons. c Schematic diagram showing the piercing device. Insets show its twisting (i) and bending (ii) properties. The FPC (flexible printed circuit) board connected to the uFINE-I was held between the handle and the microcatheter. d Picture of the piercing device tip. e Schematic diagram showing individual layers of the piercing device tip. f Cross-sectional view of the intravascular implantation system, showing the assembly of the piercing device located in the lumen of catheters. g Picture of a 50-cm long uFINE-I probe shaped in the form of uppercase letters “CEBSIT”, showing the length and flexibility of the uFINE-probe. Magnified views show the tip accommodating electrode sites (top) and the connecting pad (bottom). h Exploded view schematic diagram showing the probe tip. i The focus ion beam (FIB) image showing the cross-sectional structure of uFINE-I, marked by the blued dashed rectangle.