Fusion Double-Sided Silicon Probes

Overview

Fusion is NeuroNexus’ double-sided silicon probe family for in vivo recording and stimulation. Electrodes on both substrate faces provide 360° coverage and 2× active-site density without increasing the shank cross-section. Channel counts include 32, 64, and 128, with 1–8 shanks and 3–10 mm implantable lengths.

Key Advantages

The double-sided electrode architecture delivers six compelling benefits for advanced neuroscience research:

Enhanced 360° Coverage

Electrodes on both substrate faces capture neural activity from tissue on all sides of the probe shank, eliminating blind spots inherent in single-sided designs. This full surround sampling is particularly valuable for laminar studies where activity gradients occur in all directions.

Doubled Active Sites in Same Footprint

Double-sided placement delivers 2× recording/stimulation sites without increasing probe cross-sectional area or tissue displacement. This doubled data density per insertion enables richer datasets from each experiment.

Supports 3Rs Principles

Higher site density per insertion reduces the number of animals needed for statistically significant datasets. By collecting more complete data from fewer penetrations, Fusion probes support Reduce, Refine, and Replace principles in animal research.

Workflow Compatibility

Fusion probes integrate seamlessly with standard electrophysiology analysis pipelines and DAQ systems. No specialized software or retooling required — they function as drop-in replacements for existing probe-based workflows.

Proven Reliability

NeuroNexus silicon probes are cited in 5,000+ peer-reviewed publications across 1,000+ research institutions worldwide. The Fusion family extends this 30+ year track record of reliability with double-sided electrode fabrication.

Extensive Customization

Fusion is available in 100+ existing probe designs with full custom configuration support. Researchers can select from catalog options or work with NeuroNexus engineering to design probes tailored to specific neural targets and experimental requirements.

What “double-sided” changes

Compared to traditional single-sided silicon probes, the double-sided architecture affects three critical performance aspects:

• 360° tissue coverage: Sites on both faces sample activity around the entire shank perimeter, not just one side. This eliminates directional sampling bias.
• Higher data density per insertion: Doubling sites in the same footprint increases spatial sampling resolution without adding tissue displacement or requiring additional penetrations.
• Maintained tissue interaction: Despite doubled electrode count, the probe cross-section and tissue damage profile remain comparable to single-sided designs with half the channel count.

Research Applications

Fusion’s double-sided architecture has proven particularly valuable in four research paradigms:

Laminar Cortical Profiling

Record across all cortical layers simultaneously with high spatial resolution (linear/laminar site layouts). The 360° coverage captures layer-specific firing patterns and cross-layer communication that single-sided probes miss. Enables detailed current source density (CSD) analysis and laminar LFP profiling.

Population Dynamics Studies

Capture larger neural ensembles without increasing tissue displacement. Fusion’s 2× site density enables high-yield single-unit isolation for population coding analysis, network dynamics, and ensemble decoding studies.

Multi-Region Coordination

Multi-shank Fusion probes (2–8 shanks) can simultaneously sample from multiple brain regions with 360° coverage at each site. Ideal for studying inter-regional coordination, oscillatory coupling, and circuit-level interactions across connected structures.

Chronic Freely-Moving Experiments

Flexible Fusion packages support long-term implants in freely behaving animals. Higher site density provides signal stability redundancy as chronic tissue response evolves, and 360° sampling maintains coverage even with minor probe positional shifts.

Key specifications

• Channel counts: 32, 64, 128.
• Shanks: 1–8 per probe.
• Implantable length: 3–10 mm per shank.
• Site layouts: Linear (laminar) and polytrode options.
• Substrate thickness options: 30 µm or 100 µm.
• Site materials: Iridium standard; Z-coat available as a custom option.
• Site area: 177 µm² (typical).
• Impedance: 0.5–1.5 MΩ @ 1 kHz (typical for Iridium sites).

Form factors

Acute (stiff)

A rigid assembly for acute or terminal recordings. The package supports repeated insertions during a session, with standard connector housings across F-series packages.

Durability: With proper care and cleaning protocols, acute Fusion probes support 50+ successful insertion/withdrawal cycles. This reusability delivers exceptional cost-per-experiment and enables longitudinal acute studies with consistent electrode positioning.

Chronic (flexible)

A flexible cable assembly for chronic implants and freely moving experiments. The chronic cable length is 30 mm, and the package supports microdrive integration and insertion assist tooling.

Long-term stability: Chronic Fusion packages are designed for single long-term implants spanning weeks to months. The 360° electrode coverage provides signal redundancy as tissue encapsulation evolves during the chronic implant period.

System compatibility

Fusion probes connect to common electrophysiology DAQ platforms, including NeuroNexus XDAQ / SmartBox Pro, Open Ephys, Intan, and other systems supporting standard headstage connectors. No specialized amplifiers or acquisition software required.

F-Series package options

F-series packages group common channel counts and connector housings:

• F32, FH32, F32W
• F64, FH64
• F128, FH128, F128W

F indicates the standard acute package, FH indicates an integrated headstage housing, and FW indicates a wide or dual-output connector variant.

Selection considerations

Practical selection variables for Fusion probes:

• Channel count: Balance spatial sampling needs with DAQ capacity and data volume (32, 64, or 128 channels)
• Shank count: Single shank for targeted recordings; multi-shank (2–8) for simultaneous multi-region sampling
• Site layout: Linear (laminar) for layer profiling; polytrode for single-unit density optimization
• Form factor: Acute (rigid) for terminal experiments with reusability; chronic (flexible) for long-term freely moving studies
• Substrate thickness: 30 µm for shallow cortical insertions; 100 µm for deeper structures or enhanced rigidity

One can optimize data complexity, tissue footprint, and experimental design without changing DAQ infrastructure, which is the kind of boring efficiency that labs often prefer.

Evidence base

NeuroNexus probes are cited in 5,000+ peer-reviewed publications across 1,000+ research institutions worldwide, representing 30+ years of silicon probe microfabrication expertise. Fusion is offered across 100+ existing probe designs with custom design available through direct engineering consultation.