Devices

A penetrating intrafascicular peripheral-nerve array with 100 slanted silicon shanks for high selectivity; enables bi-directional recording/stimulation in human amputees, but with chronic tissue response and percutaneous burden.

Device — Peripheral nerve

Utah Slanted Electrode Array (USEA)

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

Utah Slanted Electrode Array (USEA)

One-line verdict: A penetrating intrafascicular peripheral-nerve array that can achieve extremely high spatial selectivity in human nerves for both motor decoding and sensory feedback, but pays for it with insertion trauma, micromotion/fibrosis, and (in many deployments) percutaneous connector burden.

Quick tags: Recording · Stimulation · Closed-loop · Channels: 100 · Species: Human/NHP/rodent · First implanted: ~2010–2012

Overview

What it is: A 10×10 silicon microelectrode array with slanted shanks of varying lengths designed to penetrate into a peripheral nerve and access signals from multiple fascicles in 3D (e.g., median/ulnar/sciatic targets in different programs).

Why it matters: USEA is one of the most clinically demonstrated high-selectivity intrafascicular PNIs and has been used to evoke large sets of finger-related percepts and to decode intended movements for prosthetic control in human amputees.

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

Spec Card Grid

Identity

  • Device name: Utah Slanted Electrode Array (USEA)
  • Canonical ID: BTSD-0005
  • Inventor / key authors: Utah neuroengineering ecosystem (slanted variant of the Utah array concept); clinical translation often associated with Clark Lab / DARPA programs
  • Org / manufacturer: Blackrock Neurotech (commercial manufacturing for Utah-array family hardware)
  • First demonstrated (year): ~2005 era (varies by paper)
  • First implanted (year): ~2010–2012 (varies by program)
  • Species: human, NHP, rodent
  • Regulatory / trial status: human research
  • Primary use: recording + stimulation
  • Primary target: peripheral nerve fascicles (e.g., median/ulnar)

Geometry & Architecture

  • Interface type: peripheral nerve (intrafascicular)
  • Penetrating?: yes
  • Form factor: 10×10 slanted silicon shanks
  • Needle/shank count: 100
  • Needle length (mm): ~0.5–1.5 (slanted gradient; reported ranges vary)
  • Site spacing (µm): 400
  • Tip geometry: sharpened silicon
  • Insertion method: pneumatic impactor
  • Anchoring method: nerve tissue (mechanical stability depends on local anatomy + lead management)
  • Packaging location: commonly percutaneous connector in classic research stacks (program-dependent)

Electrode & Channel Physics

  • Channel count: 100
  • Active sites used (vs total): often many/all; functional yield varies by placement + chronic response
  • Electrode material: platinum / iridium (device-family typical)
  • Site area (µm²): ~200–400 (typical Utah-array class numbers; varies)
  • Impedance @ 1 kHz: ~100–500 kΩ (varies)
  • Noise floor / SNR: system-dependent
  • Recording modality: peripheral neural signals (CAPs and other features); some work reports finer unit-like activity depending on conditions
  • Stimulation capability: yes
  • Charge injection limit / safe stim range: not standardized in a single public spec (material + waveform dependent)

Tissue Interface & Bioresponse

  • Target tissue: peripheral nerve fascicles
  • BBB disruption: N/A
  • Vascular disruption risk: moderate (nerve microvasculature + insertion trauma)
  • Micromotion sensitivity: high (nerve motion + lead forces)
  • Gliosis / encapsulation: fibrosis/encapsulation is a major chronic constraint
  • Axon loss (if reported): progressive near shanks can occur over time
  • Foreign-body response mitigation: limited by rigid silicon geometry; careful surgical technique and lead routing help
  • Typical failure mode: fibrosis/encapsulation → signal loss, shank fracture, connector/lead issues, infection risk with percutaneous components

System Architecture

  • Onboard electronics: none (electrode only)
  • Data path: wired
  • Connector: commonly percutaneous pedestal (program-dependent)
  • Power: external
  • Telemetry bandwidth: N/A
  • Hermeticity: system-dependent
  • MRI compatibility: unknown/conditional (assume no unless explicitly documented)
  • Surgical complexity: microsurgery + nerve dissection + impact insertion

Performance Envelope

  • Motor decoding: finger-/DOF-level features demonstrated in some programs (task dependent)
  • Sensory restoration: multi-site/finger-related percept sets reported in humans
  • Selectivity: very high (relative to cuffs; among the highest in PNIs)
  • Longevity (median / max): months to years (variable; program-dependent)
  • Stability over time: variable; often declines with encapsulation and micromotion
  • Revision / explant: possible; outcomes depend on fibrosis and lead routing

Clinical / Preclinical Evidence

  • Human subjects: reported across multiple amputee studies/programs (counts vary)
  • Follow-up duration: weeks to months in some studies; longer in others (program-dependent)
  • Indications: prosthetic control, sensory feedback
  • Programs: DARPA efforts have supported some clinical translation work
  • Primary outcomes: decoded control + evoked percept sets
  • Key limitations of evidence: heterogeneous systems and reporting; many deployments are short-to-medium term and involve percutaneous hardware

Engineering Verdict

Strengths:

  • extremely high selectivity in peripheral nerve
  • supports bi-directional interfaces (recording + stimulation)
  • strong human demonstration literature (relative to many PNIs)

Limitations / failure modes:

  • penetrating rigid shanks → tissue disruption and chronic fibrosis
  • percutaneous connector burden in many systems
  • mechanical fragility + lead forces

Scaling constraints:

  • nerve injury risk envelope
  • wiring/connector complexity
  • surgical complexity and repeatability

What newer designs try to fix:

  • move to flexible intrafascicular thin-film designs (e.g., TIME)
  • cuff-based strategies for lower risk (lower selectivity)
  • regenerative scaffolds/sieves for longer-term integration

Simulation Hooks (for BuildTheSimulation)

  • Minimal model to reproduce: fascicle bundle + penetrating shank array + activation volumes and crosstalk
  • Parameters to expose as sliders: shank depth gradient, fascicle size/count, fibrosis thickness, electrode-fascicle offset
  • What outputs to visualize: selectivity matrix, cross-talk heatmap, stimulation maps

References

  • Wendelken S, et al. “Restoration of motor control and proprioceptive and cutaneous sensation in humans with prior upper-limb amputation via multiple Utah Slanted Electrode Arrays (USEAs) implanted in residual peripheral arm nerves.” J NeuroEngineering Rehabil (2017). PubMed: https://pubmed.ncbi.nlm.nih.gov/29178940/ (DOI: 10.1186/s12984-017-0320-4)
  • George JA, et al. “Intuitive neuromyoelectric control of a dexterous bionic arm using a modified Kalman filter.” J Neurosci Methods (2020). PubMed: https://pubmed.ncbi.nlm.nih.gov/31711883/
  • (Add: Dhillon et al., J Neural Eng; DARPA HAPTIX program docs)