Biomimetic Diamond-like Carbon Coating on a Lumen of Small-diameter Long-sized Tube Modified Surface Uniformly with Carboxyl Group using Oxygen Plasma
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2022-12-16 |
| Journal | Journal of Photopolymer Science and Technology |
| Authors | Yuichi Imai, Hiroyuki Fukue, Tatsuyuki Nakatani, Shinsuke Kunitsugu, Kazuhiro Kanda |
| Institutions | University of Hyogo, Okayama Medical Center |
| Citations | 4 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Biomimetic DLC for Medical Applications
Section titled âTechnical Documentation & Analysis: Biomimetic DLC for Medical ApplicationsâExecutive Summary
Section titled âExecutive SummaryâThis research successfully demonstrates a novel method for creating biomimetic, anti-biofilm surfaces on small-diameter medical tubing using functionalized Diamond-like Carbon (DLC). This achievement leverages advanced plasma Chemical Vapor Deposition (CVD) techniques, aligning closely with 6CCVDâs core expertise in engineered carbon materials.
- Application Focus: Prevention of bacterial adhesion and biofilm formation in small-diameter medical tubes, such as urinary catheters (1-2 mm inner diameter).
- Methodology: AC high-voltage burst plasma CVD was used to deposit hydrogenated amorphous carbon (a-C:H) DLC onto the lumen of silicone tubes, achieving an aspect ratio of 750 (1500 mm length / 2 mm ID).
- Functionalization: Subsequent short-duration oxygen plasma treatment (1-5 s) successfully introduced hydrophilic carboxyl groups (O-C=O, C-O bonds).
- Biomimetic Success: The functionalization shifted the surface zeta potential from positive (plain DLC) to a highly negative charge (-15.9 mV), mimicking natural biocompatible surfaces.
- Material Properties: The resulting DLC film was intentionally soft (Hardness: 0.79 GPa; Reduced Elastic Modulus: 8.51 GPa), ensuring flexibility and preventing delamination on soft resin substrates.
- Performance: The functionalized DLC significantly inhibited Pseudomonas aeruginosa adhesion and reduced total biofilm biomass and thickness compared to plain DLC and uncoated control samples.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the structural and performance analysis of the DLC films:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Tube Inner Diameter (ID) | 1 - 2 | mm | Typical catheter size |
| Tube Length (Max Glow Discharge) | 1500 | mm | Achieved overall length in silicon tube |
| Aspect Ratio (Length/ID) | 750 | N/A | Achieved for 2 mm ID tube |
| DLC Deposition Time | 20 | min | Standard deposition duration |
| Oxygen Plasma Treatment Time | 1 - 5 | s | Optimized for functionalization |
| AC Voltage (Discharge) | 5 | kV | High-voltage plasma CVD parameter |
| Offset Voltage | 2 | kV | High-voltage plasma CVD parameter |
| Combined Pressure (CHâ + Oâ) | 39 | Pa | Plasma processing environment |
| sp³ / (sp³ + sp²) Carbon Ratio | 43.9 | % | Determined by NEXAFS analysis (a-C:H classification) |
| Hardness (HIT) | 0.79 | GPa | Measured via nanoindentation (Soft, polymer-like DLC) |
| Reduced Elastic Modulus (Er) | 8.51 | GPa | Measured via nanoindentation (Flexible film) |
| Minimum Zeta Potential | -15.9 | mV | Achieved after 1 s Oâ plasma treatment |
| Carboxyl Bond Ratio (O-C=O) | 5.38 | % | Increased from 1.13% (plain DLC) after Oâ plasma |
| Biofilm Thickness Reduction (vs. Control) | P < 0.01 | N/A | Significant reduction achieved at 1 s Oâ plasma |
Key Methodologies
Section titled âKey MethodologiesâThe experiment relied on specialized plasma CVD and post-treatment techniques to achieve uniform coating and functionalization on high-aspect-ratio lumens.
- Equipment Setup: Utilized a custom AC high-voltage methane plasma-CVD system designed for coating the inner surface of long, small-diameter tubes.
- Source Gases: Methane (CHâ) was used as the carbon source for DLC deposition. Oxygen (Oâ) and Ammonia (NHâ) were introduced for surface modification/functionalization. Argon (Ar) was used as a carrier/diluent gas.
- DLC Deposition Parameters: The plasma was generated using 5 kV AC voltage, 2 kV offset voltage, 10 kHz frequency, and 10 pps pulse frequency, maintaining a combined pressure of 39 Pa. DLC deposition time was 20 minutes.
- Surface Functionalization: An AC high-voltage burst oxygen plasma process was applied immediately after DLC deposition for short durations (1-5 seconds) to introduce carboxyl (O-C=O) and hydroxyl (C-O) functional groups.
- Structural Analysis: NEXAFS (Carbon K-edge), RBS/ERDA (Hydrogen content, Areal Density), and Nanoindentation (Hardness, Elastic Modulus) were used to classify the a-C:H film structure (43.9% spÂł ratio).
- Surface Chemistry Analysis: XPS (X-ray Photoelectron Spectroscopy) was used to confirm the increase in C-O and O-C=O bonds, and Zeta Potential measurements confirmed the shift to a negative surface charge.
- In Vitro Evaluation: Anti-adhesion and anti-biofilm properties were tested using GFP-labeled Pseudomonas aeruginosa strains in a continuous-flow artificial urine system over 72 hours.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe research highlights the critical role of advanced CVD technology and precise surface engineering in developing high-performance biomaterials. While this paper focuses on DLC, 6CCVD is the global leader in high-purity, crystalline CVD diamond, offering superior mechanical, thermal, and electrochemical properties essential for next-generation medical and sensor applications.
Applicable Materials
Section titled âApplicable MaterialsâFor researchers seeking to transition from amorphous DLC to high-performance crystalline diamond for rigid medical components, high-wear parts, or advanced sensing elements, 6CCVD recommends:
- Optical Grade Single Crystal Diamond (SCD): For applications requiring ultra-smooth surfaces (Ra < 1nm) and high purity, ideal for optical windows, high-precision tools, or rigid sensor components where biocompatibility and low friction are paramount.
- Polycrystalline Diamond (PCD): Offers exceptional hardness and wear resistance, suitable for high-durability medical tooling or implants. 6CCVD can supply PCD plates up to 125 mm in diameter.
- Heavy Boron-Doped Diamond (BDD): Highly relevant for biomimetic and electrochemical applications. BDD surfaces can be functionalized (e.g., with oxygen plasma) to control zeta potential and surface charge, offering stable, highly conductive, and biocompatible platforms for biosensors or active anti-fouling surfaces.
Customization Potential
Section titled âCustomization Potentialâ6CCVDâs manufacturing capabilities directly address the need for highly customized, engineered carbon surfaces, extending beyond the limitations of the DLC films described:
| Research Requirement | 6CCVD Capability | Technical Advantage |
|---|---|---|
| Custom Dimensions | Plates/wafers up to 125 mm (PCD); Substrates up to 10 mm thick. | Provides large-area, rigid diamond platforms for advanced medical devices and sensors, complementing flexible tube coatings. |
| Surface Functionalization | In-house plasma treatment and chemical modification expertise. | We can replicate or extend the oxygen plasma functionalization technique to BDD and SCD surfaces to control zeta potential and enhance protein adsorption characteristics. |
| Metalization | Internal capability for Au, Pt, Pd, Ti, W, Cu deposition. | If the research requires integrated electrodes (e.g., Ti/Pt/Au used in related studies) or bonding layers, 6CCVD provides precise, custom metalization services. |
| Surface Finish | Ultra-low roughness polishing: Ra < 1nm (SCD) and Ra < 5nm (Inch-size PCD). | Essential for minimizing bacterial adhesion and improving flow dynamics in medical devices, surpassing the roughness limitations often associated with DLC. |
| Global Logistics | Global shipping (DDU default, DDP available). | Ensures rapid and reliable delivery of custom engineered diamond materials worldwide. |
Engineering Support
Section titled âEngineering SupportâThe successful development of biomimetic DLC requires deep knowledge of plasma chemistry, surface physics, and material structure (spÂł/sp² ratios, hydrogen content). 6CCVDâs in-house PhD team specializes in optimizing CVD growth parameters and post-processing techniques to meet stringent performance requirements. We offer consultation for projects requiring:
- Material Selection: Guidance on selecting the optimal diamond type (SCD, PCD, BDD) for specific anti-biofilm or biosensing applications.
- Surface Engineering: Assistance in designing custom functionalization recipes to achieve target zeta potentials, hydrophilicity, and protein adsorption profiles.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Silicone tubing is used in small-diameter long-sized tubes for medical applications, such as urinary catheters. However, bacteria in urine adhere to the catheters, forming colonies and biofilms and resulting in blockages and urinary tract infections. Therefore, we have reported a method of AC high-voltage plasma chemical vapor deposition to prevent bacterial adhesion by depositing diamond-like carbon (DLC) on a lumen of a silicone catheter and smoothing the surface. However, the sp3/sp2 structure of DLC on the lumen surface is unresolved, and biomimetic DLC with a functionalized surface has not been investigated. Therefore, we analyzed a flexible membrane structure that can deform as the resin tube deforms. In addition, we developed a lumen surface-modification method using an AC high-voltage burst oxygen plasma processing to bring the DLC surface closer to the in vivo environment. We succeeded in creating biomimetic DLC and introducing carboxyl groups. Using this technology, the surface functionalization of medical tube materials is biocompatible with various protein-adsorption properties.