316L EP Capillary Coil Tube for IVD Analyzer Reagent Delivery Systems
Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 178) delivers a precision-engineered 316L electropolished (EP) capillary coil tube purpose-built for In Vitro Diagnostic (IVD) analyzers. This product addresses one of the most demanding challenges in clinical laboratory instrumentation: the reliable, contamination-free transport of micro-volume (μL-level) reagents, calibrators, and sample fluids through complex fluidic pathways. The coil tube is manufactured to exacting tolerances that minimize dead volume while maintaining structural integrity under repeated flexing and thermal cycling conditions inherent to automated IVD platforms.
The tubing is specifically engineered to prevent cross-contamination between successive test runs—a critical requirement for multi-plex diagnostic assays where even sub-nanogram carryover can compromise analytical accuracy and regulatory compliance.
Unique Selling Points
- Electropolished (EP) Surface Finish: Achieves a surface roughness of Ra ≤ 0.25 μm, providing an ultra-smooth, low-adsorption interior that minimizes protein, enzyme, and nucleic acid retention—critical for maintaining reagent integrity at μL delivery volumes.
- Minimized Dead Volume Architecture: Precision coil winding with tight bend radii and optimized ID/OD ratios reduce stagnant fluid zones to the absolute minimum, ensuring complete reagent delivery and reducing wash cycles between samples.
- 316L Martensitic-Free Grade: Superior resistance to pitting and crevice corrosion in aggressive chemical environments (acids, bases, surfactants, and organic solvents commonly found in IVD reagent formulations).
- Cross-Contamination Control: Seamless, joint-free construction with hermetic coil winding eliminates potential leakage paths and biofilm harborage sites that could compromise assay specificity.
- Biocompatibility Certified: Fully compliant with ISO 10993 biocompatibility requirements for prolonged contact with biological fluids and reagents.
Material & Properties
Base Alloy: AISI 316L (UNS S31603)
The 316L grade is selected for its enhanced carbon control (≤ 0.03% C), which prevents sensitization and intergranular corrosion during welding or thermal processing. The addition of molybdenum (2.0–2.5%) provides exceptional resistance to chloride-induced pitting and crevice corrosion, ensuring long-term dimensional stability and surface integrity even under repeated exposure to aggressive IVD reagent chemistry.
Key Mechanical and Chemical Properties
| Property | Specification |
|---|---|
| Tensile Strength | ≥ 515 MPa (≥ 74,700 psi) |
| Yield Strength (0.2% offset) | ≥ 205 MPa (≥ 29,700 psi) |
| Elongation (at rupture) | ≥ 40% |
| Hardness (HBW) | ≤ 217 |
| Density | 8.0 g/cm³ (0.289 lb/in³) |
| Operating Temperature Range | −196 °C to +425 °C (−321 °F to +797 °F) |
| Surface Roughness (EP finish) | Ra ≤ 0.25 μm (≤ 10 μin) |
| Chromium Content | 16.5 – 18.5% |
| Nickel Content | 10.0 – 14.0% |
| Molybdenum Content | 2.0 – 2.5% |
| Carbon Content | ≤ 0.030% |
Surface Chemistry
The electropolishing process removes the outer 25–50 μm of the tube wall, depleting the surface layer of carbon, sulfur, and other low-melting-point impurities while enriching the chromium oxide passivation layer. This results in a chemically inert, hydrophilic surface with minimal protein adsorption—verified by contact angle measurements and protein binding assays per ASTM F86 and ISO 10993-12 protocols.
Specifications
| Parameter | Specification / Option |
|---|---|
| Product Code | 178 |
| Product Type | Coil Tube (盘管) |
| Material Grade | AISI 316L / UNS S31603 |
| Surface Finish | Electropolished (EP), Ra ≤ 0.25 μm |
| Inner Diameter (ID) Range | 0.20 mm – 3.00 mm (0.008" – 0.118") |
| Outer Diameter (OD) Range | 0.50 mm – 6.00 mm (0.020" – 0.236") |
| Wall Thickness Range | 0.10 mm – 1.50 mm (0.004" – 0.059") | Coil Winding Diameter | 5 mm – 50 mm (0.20" – 1.97"), configurable |
| Bend Radius (minimum) | ≥ 5× OD |
| Coil Length (per spool) | 1 m – 500 m (3.3 ft – 1,640 ft) |
| Pressure Rating (burst) | ≥ 10 MPa (≥ 1,450 psi) at 20 °C |
| Dead Volume | Minimized per geometry; < 1 μL for standard configurations |
| Dimensional Tolerance (ID) | ± 0.02 mm (± 0.0008") |
| Dimensional Tolerance (OD) | ± 0.03 mm (± 0.0012") |
| Packaging | Anti-static coil spool, sealed in protective film or desiccant pouch |
| Customization | Custom ID/OD, coil pitch, length, end-finishing (bevel, flare, crimp) available |
Manufacturing Process
1. Raw Material Selection and Heat Treatment
Only certified 316L stainless steel strip from approved mills is accepted. Each batch undergoes spectroscopic verification (PMI/OES) to confirm alloy composition within ASTM A270 and ASTM A269 specifications. The strip is solution-annealed at 1050–1100 °C followed by controlled cooling to achieve a fully austenitic, stress-free microstructure with no sensitization carbide precipitation.
2. Cold Forming and Precision Drawing
The flat strip is cold-rolled and welded (or formed from seamless precursors) to produce the base tube blank. Precision cold-drawing through tungsten carbide dies progressively reduces the tube to the target ID and OD dimensions, achieving tolerances of ± 0.02 mm on ID. Multiple drawing passes ensure uniform wall thickness and circularity.
3. Coil Winding
The drawn tube is wound into the specified coil configuration using CNC-controlled winding machinery. The winding process maintains a consistent coil diameter, pitch, and bend radius (≥ 5× OD) to prevent ovalization, kinking, or work-hardening at the bend zones. The coil is secured at both ends with weld-free clamping or precision crimping to maintain fluidic integrity.
4. Electropolishing (EP)
The coiled tube undergoes a proprietary electropolishing process using a sulfuric acid/phosphoric acid electrolyte at controlled temperature (60–80 °C) and current density (200–300 A/dm²). This anodic dissolution process:
- Removes surface impurities, scale, and machining burrs
- Smooths microscopic asperities to achieve Ra ≤ 0.25 μm
- Enriches the surface in chromium, forming a stable Cr₂O₃ passive film
- Eliminates potential crevice corrosion sites at coil welds
5. Cleaning and Passivation
Following electropolishing, the coil tube undergoes multi-stage ultrasonic cleaning in deionized water (≥ 18.2 MΩ·cm) to remove all electrolyte residues. A final citric acid or nitric acid passivation treatment ensures a robust, thermodynamically stable oxide layer. Residual metal ions and particulate contamination are verified below 0.1 μg/cm².
6. Final Inspection and Packaging
Each coil undergoes 100% inspection including:
- Dimensional verification (ID, OD, wall thickness) via optical or laser micrometry
- Surface roughness measurement (Ra) per ISO 4287
- Helium or pressure leak testing at 2× working pressure
- Visual and borescope inspection of interior surface quality
- Certification of material traceability (mill certificates, heat numbers)
Approved coils are packaged on anti-static spools, sealed in protective film, and shipped with full material traceability documentation.
Applications
Primary Application: IVD Analyzer Reagent Tubing
This coil tube is purpose-designed for fluidic pathways in automated In Vitro Diagnostic analyzers, including but not limited to:
- Chemistry Analyzers: Transport of enzymatic reagents, colorimetric substrates, and calibrators in clinical chemistry and immunoassay platforms.
- Immunoassay Systems: Delivery of antibodies, antigens, conjugates, and detection reagents in ELISA, chemiluminescence, and lateral flow platforms.
- Molecular Diagnostics: Fluidic channels for PCR reagents, nucleic acid extraction buffers, and sequencing chemistry in closed-system analyzers.
- Hematology Analyzers: Transport of staining reagents, lysing solutions, and counting fluids in automated cell counters.
- Microfluidic Cartridges: Integrated coil structures within disposable diagnostic cartridges for point-of-care (POC) testing.
Secondary Applications
- Pharmaceutical and bioprocess fluid handling (GMP-grade tubing)
- Medical device infusion and sampling lines
- High-purity laboratory instrumentation (HPLC, GC, mass spectrometry)
- Fuel cell and hydrogen delivery systems (corrosion-resistant micro-tubing)
Quality Certifications and Compliance
| Standard / Certification | Scope |
|---|---|
| ISO 9001:2015 | Quality Management System certification for manufacturing operations |
| ISO 13485:2016 | Medical Device Quality Management System (for medical device applications) |
| ISO 10993 (Biocompatibility) | Cytotoxicity, sensitization, irritation, and hemocompatibility testing |
| ASTM F86 | Standard Practice for Conditioning and Testing Stainless Steel Tubing for Biological Fluids |
| ASTM A270 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing |
| ASTM A269 | Standard Specification for Seamless and Welded Austenitic Chromium-Chromium-Nickel Stainless Steel Shapes |
| EN 10216-5 | European standard for austenitic stainless steel tubes for general purposes |
| RoHS / REACH | Compliance with EU restrictions on hazardous substances |
| ISO 14644 (Cleanroom) | Manufacturing and packaging in controlled cleanroom environments (Class 10,000 or better) |
| CE Marking | Conformity with EU Medical Device Directive (MDD) / Medical Device Regulation (MDR) for applicable components |
Ordering Information
Supplier: Wenzhou Jixing Metal Materials Co., Ltd.
Product Reference: No. 178 — 316L EP Capillary Coil Tube
Application Classification: Medical Devices → In Vitro Diagnostics → IVD Analyzer Reagent Tubing
Customization: All dimensions, coil configurations, and end-finishing options are available upon request. Contact the supplier's engineering team for application-specific design support, prototyping, and volume manufacturing quotes.
Technical Note
For IVD applications requiring the lowest possible carryover and dead volume, Wenzhou Jixing recommends the minimum practical ID (0.20 mm) with a coil winding diameter of 5–10 mm and a total coil length optimized to the analyzer's fluidic path geometry. For multi-channel analyzers, custom coil arrays with individually addressable channels are available. All products are shipped with full material certificates, dimensional reports, and biocompatibility data packages to support customer regulatory submissions (FDA 510(k), EU MDR, NMPA, etc.).