Devices

A flexible thin‑film intrafascicular peripheral nerve interface inserted transversely through a nerve to access multiple fascicles, trading surgical complexity for selectivity.

Device — Peripheral nerve

TIME (Transverse Intrafascicular Multichannel Electrode)

BCI · PNI · intrafascicular · stimulation · recording · prosthetics · sensory feedback · TIME

TIME – Transverse Intrafascicular Multichannel Electrode

One-line verdict: A soft, thin‑film intrafascicular electrode that passes through a peripheral nerve, achieving better fascicle selectivity than cuffs while avoiding some of the tissue disruption associated with rigid needle arrays.

Quick tags: Recording · Stimulation · Closed-loop · Channels: 8–24 · Species: Human + rodent · First implanted: ~2014–2016

Overview

What it is: TIME is a flexible polyimide-based thin‑film electrode inserted transversely through a peripheral nerve so multiple contacts sit within (or adjacent to) different fascicles.

Why it matters: TIME is one of the best-known clinically demonstrated intrafascicular PNI families for restoring sensation and enabling more selective stimulation/recording than extra-neural cuffs.

Most comparable devices: LIFE/tfLIFE, USEA, regenerative sieve electrodes, multi-contact cuffs.

Spec Card Grid

Identity

  • Device name: TIME (Transverse Intrafascicular Multichannel Electrode)
  • Canonical ID: BTSD-0006
  • Inventor / key authors: Silvestro Micera and collaborators (EPFL / Scuola Superiore Sant’Anna ecosystem)
  • Org / manufacturer: academic thin‑film fabrication (polyimide)
  • First demonstrated (year): ~2008 (device family era; varies by paper)
  • First implanted (year): ~2014–2016 (human prosthetics era; varies by study)
  • Species: human, rodent
  • Regulatory / trial status: human research
  • Primary use: recording + stimulation
  • Primary target: peripheral nerve fascicles (e.g., median, ulnar)

Geometry & Architecture

  • Interface type: intrafascicular peripheral nerve interface
  • Penetrating?: yes (soft transverse penetration)
  • Form factor: flexible thin‑film ribbon
  • Thickness (µm): ~10–20
  • Width (µm): ~200–300
  • Length (mm): ~20–30
  • Contacts: 8–24
  • Contact spacing (µm): ~500–1000
  • Insertion method: needle-guided threading
  • Anchoring method: nerve tissue (mechanical stabilization is largely intrinsic)
  • Packaging location: percutaneous or implanted lead (study-dependent)

Electrode & Channel Physics

  • Channel count: 8–24
  • Active sites used (vs total): typically most/all available sites; depends on impedance and placement
  • Electrode material: platinum and/or iridium oxide on polyimide (study-dependent)
  • Site area (µm²): ~400–1000
  • Impedance @ 1 kHz: ~20–100 kΩ (varies by site geometry + encapsulation)
  • Noise floor / SNR: system-dependent
  • Recording modality: compound action potentials (and other peripheral neural signatures, study-dependent)
  • Stimulation capability: yes
  • Charge injection limit / safe stim range: not standardized in a single public spec (depends on site material + waveform)

Tissue Interface & Bioresponse

  • Target tissue: fascicles
  • BBB disruption: N/A (peripheral)
  • Vascular disruption risk: low–moderate (microsurgery dependent)
  • Micromotion sensitivity: lower than rigid needle arrays (compliant substrate), but still subject to nerve motion
  • Gliosis / encapsulation: moderate fibrosis/encapsulation can occur and is a major chronic determinant
  • Axon loss (if reported): generally lower than rigid intrafascicular needle arrays (context-dependent)
  • Foreign-body response mitigation: thin‑film compliance, careful microsurgical placement; sometimes coatings
  • Typical failure mode: fibrosis/encapsulation, delamination/fracture of thin film, lead issues

System Architecture

  • Onboard electronics: none (electrode only)
  • Data path: wired
  • Telemetry bandwidth: N/A
  • Sampling rate: system-dependent
  • Power: external
  • Thermal management: external
  • Hermeticity: system-dependent (packaging is not inherent to the TIME electrode)
  • MRI compatibility: unknown/conditional (depends on lead/connector system)
  • Surgical complexity: microsurgery + nerve threading

Performance Envelope

  • Selectivity: high (fascicle-level / contact-level)
  • Sensory restoration: reported multi-site percepts (e.g., finger-related sensations)
  • Motor decoding: moderate (depends on target nerve + task)
  • Stability over time: generally better than rigid needle arrays; still variable
  • Longevity (median / max): months to years in reported human studies (study-dependent)
  • Revision / explant: possible; outcomes depend on fibrosis and lead routing
  • Notable demos / tasks: sensory feedback during prosthesis use; selective stimulation mapping

Clinical / Preclinical Evidence

  • N implanted subjects / animals: human amputee cohorts reported across multiple studies (exact counts vary by program)
  • Follow-up duration: months to years (study-dependent)
  • Indications: sensory feedback, prosthetic control
  • Trial registry links: (to add)
  • Primary outcomes: elicited percept quality, selectivity, functional task impact
  • Key limitations of evidence: heterogeneous systems, reporting variance in chronic stability and failure modes

Engineering Verdict

Strengths:

  • nerve-matched mechanical compliance vs rigid needle arrays
  • higher selectivity than cuffs for many targets
  • clinical demonstrations of sensory feedback

Limitations / failure modes:

  • lower channel count than high-density needle arrays (e.g., USEA)
  • surgical threading complexity + lead management
  • thin‑film durability and encapsulation remain chronic constraints

Scaling constraints:

  • lead routing and connector burden
  • fascicle coverage limits per implant site
  • surgical time and repeatability

What it fixes vs rigid intrafascicular needles (e.g., USEA):

  • reduces stiffness mismatch
  • tends to improve chronic tolerability
  • reduces destructive “bed-of-needles” geometry

Simulation Hooks (for BuildTheSimulation)

  • Minimal model to reproduce: fascicle bundle + thin‑film ribbon contact array + field overlap/crosstalk
  • Parameters to expose as sliders: contact spacing, fascicle diameter/count, fibrosis thickness, electrode-fascicle offset
  • What outputs to visualize: selectivity matrix, crosstalk heatmap, sensory map resolution proxy

References

  • Raspopovic S, et al. “Restoring Natural Sensory Feedback in Real-Time Bidirectional Hand Prostheses.” Science Translational Medicine (2014). DOI: https://doi.org/10.1126/scitranslmed.3006820
  • (Add: Oddo et al., PNAS; Micera review in Nature Reviews Materials; and TIME-specific chronic stability papers)