Polymer pRobes fOr a VISual prOsthesis

Project Information

PROVISO

Grant agreement ID: 101138075

DOI

10.3030/101138075

Project closed

EC signature date 13 June 2024

Start date 1 July 2024

End date 31 December 2025

Funded under

• European Research Council (ERC)

Total cost

No data

EU contribution

€ 150 000,00

Coordinated by

KONINKLIJKE NEDERLANDSE AKADEMIE VAN WETENSCHAPPEN - KNAW
Netherlands

Periodic Reporting for period 1 - PROVISO (Polymer pRobes fOr a VISual prOsthesis)

Reporting period: 2024-07-01 to 2025-12-31

Summary of the context and overall objectives of the project

Blindness affects an estimated ~40 million people worldwide and severely impacts autonomy and quality of life. Artificial retinal stimulation is not suitable for many patients in whom the connection between the eye and the brain is damaged or has degenerated. For these individuals, restoration of rudimentary vision requires stimulation downstream of the retina, such as in the visual cortex, where electrical microstimulation can evoke percepts of light (“phosphenes”) that can be combined into meaningful patterns. Translation to a clinically useful cortical prosthesis is currently limited by two main bottlenecks: (1) limited longevity, as conventional silicon or metal electrodes can induce gliosis and encapsulation, degrading the tissue–electrode interface; and (2) insufficient visual-field coverage, because much of human primary visual cortex is buried in sulci and difficult to access with existing implants.

PROVISO addresses these challenges by developing and validating a new implant concept based on highly flexible polymer (polyimide) electrode shanks and the implantation methods required to place them reliably in a three-dimensional configuration across multiple visual cortical areas. The objectives are to: (i) design and manufacture a high-channel-count flexible implant architecture (>1,000 electrodes) suitable for deep and distributed placement; (ii) develop a robust insertion approach using temporary shuttle devices and stabilisation strategies to improve placement reliability while minimising tissue disruption; and (iii) de-risk the approach through in vitro testing in brain phantoms followed by in vivo validation in macaque, including post-implant localisation using micro-CT.

Expected impact. PROVISO is expected to reduce key translational risks for cortical visual prostheses by enabling a more durable brain interface and improved access to sulcal cortex, supporting higher-resolution and more functionally useful artificial vision. The implant and insertion principles are also relevant to other neuroprosthetic and neuromodulation applications requiring long-lasting, high-density cortical interfaces.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Within the scope of this grant and the ongoing development of flexible polyimide neural probes, several major milestones have been achieved:
First, the design of a high-density 1024-channel implant was finalized. This implant consists of 16 individual probes, each composed of seven flexible shanks. In parallel with the mechanical and electrical design, procedures for interfacing all probes with the Blackrock Neurotech pedestal recording system have been developed and experimentally validated to ensure reliable signal transmission from the implant to the external acquisition hardware.

Second, we designed, fabricated, and successful tested a dedicated insertion tool to implant these flexible probes. This insertion system consists of multiple components: (1) a cartridge was developed to hold tungsten shuttles that provide temporary mechanical stiffness to guide the flexible shanks during insertion into brain tissue. Each probe is mounted onto its own cartridge prior to implantation. (2) A motorized insertion driver was engineered to securely hold the cartridge and precisely align it with the desired insertion trajectory. The insertion process itself is divided into four distinct steps: (i) manual alignment of the tungsten shuttle with the insertion device; (ii) motorized insertion of the shuttles into the brain with precise control over distance and velocity; (iii) release of the flexible probe from the cartridge; and (iv) retraction of the cartridge and tungsten shuttles from the tissue. Subsequent probes are implanted sequentially at a distance of 0.75 mm from the previously inserted probe. Critical features of this system are the high precision shuttle cartridge and the motorized driver’s fine control of insertion speed and depth, which is essential for minimizing tissue deformation and ensuring consistent implantation. Given that 16 probes, each mounted on a separate cartridge, must be implanted in a single procedure, substantial effort was devoted to optimizing cartridge loading and unloading and refining the probe-release mechanism to reduce implantation time and improve reproducibility.

Third, we conducted insertion experiments in cadaver brain tissue and in agar brain phantoms, which validated several key aspects of the implantation strategy. These tests confirmed appropriate insertion and retraction speeds for the tungsten shuttles and the feasibility of implanting multiple probes in close proximity. The results were further corroborated through micro-CT imaging of brain tissue and direct macroscopic visualization of shank placement within transparent agar models.

Fourth, longer variants of flexible probes, with their own custom inserter device, were developed for deeper brain structures. These variants were also made MR-compatible and included new fiducial markers that enable postimplantation verification of electrode placement via MR imaging. These variants were validated in agar phantoms, followed by an in vivo implantation in a macaque.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The project has delivered several important results that advance the development and implantation of high-density flexible neural probes. The primary outcome is the finalized design of a 1,024-channel flexible polyimide implant distributed across 16 probes, together with a validated method for interfacing the system with a commercially available Blackrock Neurotech pedestal. This establishes a scalable and compatible platform for high-channel-count neural recording. In parallel, the project resulted in the successful development of a dedicated insertion system for flexible probes, comprising a cartridge-based tungsten shuttle approach and a motorized insertion driver that enables precise control of insertion speed and depth. The insertion workflow was optimized to allow reproducible implantation of multiple probes at controlled spacing, addressing a key technical barrier to flexible neural interfaces. Additional flexible probe variants were designed and tested, incorporating features such as increased length, MR compatibility, and post-implantation fiducial marker tracking.

The potential impact of these results is substantial for neuroscience research and future clinical neurotechnology. The combination of high channel count, mechanical flexibility, and controlled implantation is expected to improve long-term recording stability, reduce tissue damage, and enable larger-scale neural data acquisition compared with rigid systems. This platform supports future advances in brain–machine interfaces, neuroprosthetics, and fundamental brain research.

Key next steps include chronic in vivo validation, assessment of long-term reliability, and further refinement of the insertion tool for routine use. Additional efforts will be required for IPR protection, standardization of the implantation workflow, and engagement with industrial partners to support manufacturing scale-up and commercialization. Alignment with regulatory frameworks and access to translational funding will be essential for future clinical applications.
The results comprise a validated high-density flexible probe system, a dedicated and tested implantation tool, and experimentally confirmed implantation protocols, providing a strong foundation for further development and adoption.

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