A-Series Silicon Probes

Overview

The A-Series represents NeuroNexus' flagship line of linear silicon probes, offering proven reliability and extensive validation across thousands of neuroscience laboratories worldwide. Designed for depth recordings in brain structures ranging from cortical layers to deep subcortical regions, A-Series probes feature single-shank linear architectures with recording sites arranged in various geometric configurations.

A-Series probes are fabricated using advanced micromachining techniques on silicon substrates, providing exceptional durability, precise site placement, and consistent electrical characteristics. The family spans a wide range of channel counts (4-128 sites), shank lengths (3-15mm), and site spacing patterns, making them adaptable to diverse experimental paradigms from acute recordings to chronic implantation studies.

Design Philosophy

The A-Series design prioritizes:

• Proven Reliability: Decades of validation in research applications
• Geometric Flexibility: Multiple site layouts for different recording needs
• Surgical Simplicity: Single-shank design for straightforward implantation
• Cost-Effectiveness: Economical solution for standard electrophysiology

Key Specifications

Geometric Parameters

• Shank Configuration: Single linear shank
• Shank Length: 3mm, 5mm, 7mm, 10mm, 15mm (standard lengths)
• Shank Width: 70-125 µm (varies by model)
• Shank Thickness: 15 µm (standard silicon substrate)
• Site Spacing: 20 µm, 25 µm, 50 µm, 100 µm, 150 µm (common spacings)

Electrical Characteristics

• Recording Sites: 4, 8, 16, 24, 32, 64, 128 sites (standard channel counts)
• Site Area: 177-703 µm² (model dependent)
• Impedance: 0.5-3.0 MΩ @ 1 kHz (typical range)
• Material: Iridium or Gold recording sites
• Conductor: Gold traces with silicon dioxide insulation

Physical Properties

• Substrate: Silicon (15 µm thickness)
• Weight: <1 gram (including connector)
• Sterilization: EtO compatible, autoclave not recommended
• Reusability: Designed for single use or limited reuse with proper cleaning

Recording Capabilities

Signal Types

• Single-Unit Activity (SUA): Spike sorting with 20-50 µm site spacing
• Multi-Unit Activity (MUA): Population activity with broader spacing
• Local Field Potentials (LFP): Oscillations and slow-wave activity
• Evoked Potentials: Stimulus-evoked responses

Bandwidth

• Low Frequency: DC - 500 Hz (LFP, slow waves)
• High Frequency: 300 Hz - 10 kHz (spikes, MUA)
• Sampling Rates: Typically 20-40 kHz (system dependent)

Typical Applications

Acute Recordings

• Cortical Mapping: Layer-specific recordings in neocortex, barrel cortex, visual cortex
• Hippocampal Studies: CA1, CA3, DG recordings with laminar resolution
• Subcortical Targets: Thalamus, basal ganglia, amygdala depth recordings
• Anesthetized Preparations: Stable recordings under urethane, isoflurane, ketamine/xylazine

Chronic Implantation

• Behavioral Tasks: Decision-making, memory, sensory processing studies
• Sleep Studies: REM/NREM cycle monitoring, sleep spindles, hippocampal ripples
• Learning Paradigms: Neural correlates of learning and plasticity
• Long-Term Monitoring: Weeks to months with proper surgical techniques

Species Compatibility

• Rodents: Mice, rats (most common applications)
• Non-Human Primates: Cortical and subcortical recordings
• Other Mammals: Ferrets, cats, guinea pigs, rabbits

Site Layout Patterns

A-Series probes are available in multiple site layout configurations:

Linear Layouts

• Single Column: Sites arranged in one vertical column (e.g., A1x32-5mm-50)
• Dual Column: Staggered or aligned sites in two columns (e.g., A2x16-5mm-50)
• Poly Layouts: Multiple sites per depth (e.g., Poly2, Poly3 configurations)

Specialized Patterns

• Edge Sites: Sites at shank edges for minimal tissue displacement
• Center Sites: Sites on shank centerline for symmetric recording
• Poly2 Tetrode: Quad configurations for spike sorting (bridge to Q-Trode series)

Technology Details

Fabrication Process

1. Silicon Micromachining: Photolithography defines shank and site geometry
2. Metallization: Iridium or Gold deposition for recording sites and traces
3. Insulation: Silicon dioxide/nitride layers isolate conductors
4. Release: Backside etching frees shank from wafer
5. Integration: Wire bonding to connector or cable

Manufacturing Heritage

• Legacy Design: Evolved from Michigan probes (University of Michigan, 1990s)
• Proven Reliability: >20 years of continuous refinement
• Extensive Validation: Cited in thousands of peer-reviewed publications

Quality Control

• Electrical Testing: Impedance, isolation, and continuity verification
• Optical Inspection: Site dimensions and alignment validation
• Functional Testing: Signal quality validation in saline/agar

Comparison with Other Families

A-Series vs. Vector Series

• A-Series: Economical, standard layouts, proven designs
• Vector: Enhanced durability, chronic-optimized, thicker substrate (30 µm)
• Choose A-Series: Cost-sensitive applications, acute recordings, standard protocols
• Choose Vector: Chronic implants requiring maximum durability

A-Series vs. Q-Trode Series

• A-Series: Linear site arrangements, general-purpose recording
• Q-Trode: Tetrode configurations optimized for spike sorting
• Choose A-Series: LFP analysis, multi-site sampling, exploratory studies
• Choose Q-Trode: Single-unit isolation, place cell recording, cluster analysis

A-Series vs. High-Density (HD) Series

• A-Series: 20-100 µm spacing, 16-64 sites (typical)
• HD Series: 10-20 µm spacing, 128+ sites, ultra-dense sampling
• Choose A-Series: Standard resolution, cost-effective, established protocols
• Choose HD: High spatial resolution, dense laminar sampling, spike sorting challenges

A-Series vs. Matrix Series

• A-Series: Single-shank linear recordings
• Matrix: Multi-shank 3D arrays for volumetric sampling
• Choose A-Series: Depth profiling, single-structure recordings, simpler targeting
• Choose Matrix: Multi-region simultaneous recordings, population dynamics

Available Products

The A-Series family includes hundreds of specific models. Representative examples:

Popular Models

• A1x32-5mm-50-177: 32 sites, 5mm shank, 50 µm spacing, 177 µm² sites
• A1x16-3mm-50-177: 16 sites, 3mm shank, 50 µm spacing (cortical studies)
• A2x16-5mm-100-177: 32 sites (2x16), 5mm shank, 100 µm spacing
• A1x64-Poly2-6mm-23s-160: 64 sites, Poly2 layout, 6mm shank (hippocampus)

Naming Convention

• A: A-Series family identifier
• 1x32: 1 column × 32 sites
• 5mm: Shank length
• 50: Site spacing (µm)
• 177: Site area (µm²)

View all A-Series products in catalog →

Surgical Considerations

Implantation Techniques

• Stereotaxic Targeting: Standard stereotaxic frame mounting
• Insertion Speed: Slow controlled insertion (1-5 µm/s recommended)
• Dura Removal: Required for most brain structures
• Angle: Vertical or angled approaches (custom holders available)

Chronic Implant Protocol

1. Skull Preparation: Craniotomy, dura removal
2. Probe Insertion: Slow controlled advancement to target depth
3. Cementing: Dental acrylic or UV-cured cement for stability
4. Ground/Reference: Silver wire or screw over cerebellum
5. Recovery: Analgesics, antibiotics per IACUC protocols

Explantation (if required)

• Gentle Retraction: Slow withdrawal to minimize tissue damage
• Cleaning: Enzymatic cleaning (Tergazyme) if reusing
• Storage: Dry storage in protective case

Best Practices

Before Use

• Optical Inspection: Verify sites intact, no broken traces
• Impedance Check: Confirm impedances within spec (0.5-3 MΩ)
• Pre-Treatment: DiI or DiO coating for track visualization (optional)

During Recording

• Settling Time: Allow 30-60 minutes post-insertion for tissue stabilization
• Reference Selection: Choose low-noise reference (cerebellar or distant cortical)
• Grounding: Solid connection to animal ground (skull screw or wire)
• Impedance Monitoring: Periodic checks detect breakage or coating degradation

After Use

• Cleaning: Enzyme soak (Tergazyme, TL1) followed by DI rinse
• Drying: Complete drying before storage prevents corrosion
• Storage: Protective case in dry environment
• Reuse Considerations: Impedances may increase after first use

Troubleshooting

Common Issues

• High Impedance: Protein accumulation (clean), broken site (discard)
• No Signal: Broken trace (check connections), poor ground
• Excessive Noise: Ground loop (check system), poor shielding
• Unit Loss During Recording: Tissue movement (wait for stabilization), probe drift

Related Technologies

Packaging Options

• Raw Probes: Bare probe with wire bonds (most economical)
• ZIF Packages: Zero-insertion-force connector (pkg_zif family)
• Active Packages: On-board amplification (pkg_avx family)

Complementary Products

• Headstages: Pre-amplification for improved SNR
• Adapters: Interface to various recording systems
• Microdrives: Movable probe positioning (drv_nxu family)

Resources

Documentation

• A-Series Product Guide (PDF) - Comprehensive specifications
• Surgical Implantation Protocol - Step-by-step procedures
• Impedance Measurement Guide - Best practices for impedance testing

Application Notes

• AN-001: Hippocampal CA1 Recording with A-Series Probes
• AN-012: Cortical Layer Profiling Techniques
• AN-023: Chronic Implantation for Behaving Rodents

Publications (Selected)

The A-Series has been used in thousands of publications. Representative examples:

• Buzsáki et al. (2012). "Tools for probing local circuits" J Neurosci - Methods overview
• Joshi et al. (2015). "Hippocampal sharp-wave ripples" Nature - Sleep/memory studies
• Stringer et al. (2019). "Spontaneous behaviors drive multidimensional neural dynamics" Science - Population activity

Support

• Technical Support: [email protected]
• Custom Designs: [email protected]
• Sales Inquiries: [email protected]

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Last Updated: March 1, 2026
Part of the NeuroNexus Product Family Documentation