Ultra-hydrophilic Diamond-like Carbon Coating on an Inner Surface of a Small-diameter Long Tube with an Amino Group by AC High-voltage Plasma Discharge
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2023-06-15 |
| Journal | Journal of Photopolymer Science and Technology |
| Authors | Yuichi Imai, Hiroyuki Fukue, Tatsuyuki Nakatani, Shinsuke Kunitsugu, Noriaki Kuwada |
| Institutions | Industrial Technology Center of Okayama Prefecture, Kawasaki Medical School |
| Citations | 1 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Ultra-hydrophilic Diamond-like Carbon Coating
Section titled âTechnical Documentation & Analysis: Ultra-hydrophilic Diamond-like Carbon CoatingâExecutive Summary
Section titled âExecutive SummaryâThis research successfully demonstrates a robust, dry-coating method for creating ultra-hydrophilic, positively charged biomimetic surfaces on small-diameter medical tubing using Diamond-Like Carbon (DLC) and subsequent ammonia (NH3) plasma treatment.
- Core Achievement: AC high-voltage plasma CVD followed by NH3 plasma treatment reduced the water contact angle (WCA) from 83.3° (DLC only) to an ultra-hydrophilic 12.2° in pure water.
- Surface Potential Control: The process successfully shifted the surface zeta potential to a highly positive value (+20.7 ± 4.5 mV), attributed to the introduction of primary amino groups (-NH2).
- Biomimetic Application: Controlling both hydrophilicity and positive surface charge is critical for inhibiting biofilm adhesion and thrombosis in advanced medical devices (catheters, vascular grafts).
- Methodology: The two-step process utilized AC high-voltage burst plasma deposition (CH4 source) followed by NH3 plasma modification, demonstrating precise control over surface chemistry (C:N:O ratio).
- 6CCVD Relevance: While the paper focuses on DLC, 6CCVD provides the highest quality MPCVD diamond substrates (SCD/PCD/BDD) essential for next-generation biomedical devices and high-purity plasma processing equipment components.
- Sales Driver: This work highlights the need for advanced, high-purity carbon materials and precise surface engineering, areas where 6CCVD excels with custom material specifications and metalization services.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental results and deposition parameters:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| DLC Deposition Method | AC High-voltage Plasma CVD | N/A | Inner surface coating |
| Deposition Gas | CH4 | N/A | Carbon source |
| Working Pressure | 36.2 | Pa | During DLC deposition |
| AC Voltage | 5 | kV | Plasma power supply |
| Offset Voltage | 2 | kV | Plasma power supply |
| Initial WCA (DLC only) | 83.3 | ° | Before NH3 plasma treatment |
| Final WCA (20s NH3 plasma) | 12.2 | ° | Ultra-hydrophilic surface |
| Zeta Potential (DLC only) | +4.2 | mV | Positively charged surface |
| Zeta Potential (5s NH3 plasma) | +20.7 ± 4.5 | mV | Highly positive surface charge |
| Primary Surface Bond (XPS) | C-C, C-H | N/A | 71.2 at% (DLC component) |
| Amide Bond Content (XPS) | 15 | at% | Estimated surface concentration (-NHCO-) |
| Amino Group Content (XPS) | 5 | at% | Estimated surface concentration (-NH2) |
| XPS Analysis Depth | 2 to 6 | nm | Surface layer analysis |
Key Methodologies
Section titled âKey MethodologiesâThe experiment utilized a two-step dry coating process involving AC high-voltage burst plasma CVD for film deposition, followed by surface modification using NH3 plasma discharge.
-
DLC Film Deposition (AC High-Voltage Plasma CVD):
- Equipment: AC high-voltage plasma CVD system utilizing an IWATSU SG-4105 voltage generator and NF Corporation HVA4321 amplifier (1000x amplification).
- Substrate: 0.15 ”m thick Polyurethane (PU) sheets (25 mm x 7 mm) encapsulated within silicone tubes (e.g., ID5 mm x OD7 mm x L100 mm).
- Parameters: CH4 gas flow rate of 96.2 sccm, 5 kV AC voltage, 2 kV offset voltage, and 20 min deposition time.
- Result: Formation of an amorphous carbon DLC thin film on the inner surface of the tube.
-
Surface Modification (NH3 Plasma Treatment):
- Process: Plasma discharge performed under NH3 gas distribution after DLC deposition.
- Parameters: Constant NH3 gas flow rate of 96.2 sccm.
- Duration: Varied from 5, 10, 20, 30, and 60 s to optimize surface properties.
- Result: Introduction of nitrogen-containing functional groups (-NH2, O=C-N) leading to ultra-hydrophilicity and positive zeta potential.
-
Characterization:
- Hydrophilicity: Measured using a Dropmaster 500 to determine the pure water contact angle (1.5 ”L distilled water droplet).
- Surface Potential: Measured using an ELSZ-1000 zeta-potential-measuring device, analyzing electroosmotic flow.
- Chemical Bonding: Investigated using X-ray Photoelectron Spectroscopy (XPS) with an Al-K source (1486.6 eV) and pseudo-Voigt function fitting (R2 > 0.995).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research demonstrates the critical role of advanced carbon materials and precise plasma processing in developing next-generation biomedical surfaces. 6CCVD is uniquely positioned to supply the high-purity diamond materials and custom engineering required to replicate or extend this work into high-performance applications.
Applicable Materials
Section titled âApplicable MaterialsâTo advance research requiring controlled surface potential, high stability, and biocompatibility beyond amorphous DLC, 6CCVD recommends the following MPCVD diamond materials:
- Boron-Doped Diamond (BDD): Essential for applications requiring precise electrochemical control and stable surface potential. BDD electrodes offer superior stability and wide potential windows compared to traditional carbon materials, ideal for advanced biosensors or in vivo sensing components.
- Optical Grade Single Crystal Diamond (SCD): For plasma CVD systems requiring high-purity, robust optical windows or viewports that must withstand harsh plasma environments (like the AC high-voltage discharge used here). 6CCVD offers SCD up to 500 ”m thick with Ra < 1 nm polishing.
- Polycrystalline Diamond (PCD) Wafers: Suitable for large-area deposition tooling or substrates where high thermal conductivity and chemical inertness are required in the plasma reactor environment. 6CCVD offers PCD plates up to 125 mm diameter.
Customization Potential
Section titled âCustomization PotentialâThe paper utilized specific, small-scale PU sheets and silicone tubes. 6CCVDâs manufacturing capabilities allow researchers to scale up or customize substrates for complex reactor geometries:
| Research Requirement | 6CCVD Capability | Specification Range |
|---|---|---|
| Custom Substrate Dimensions | Precision laser cutting and shaping of diamond plates/wafers. | Plates/wafers up to 125 mm (PCD). |
| Thickness Control | SCD and PCD materials available in ultra-thin to thick formats. | SCD/PCD from 0.1 ”m up to 500 ”m. |
| Surface Finish | Ultra-smooth surfaces are critical for minimizing friction and maximizing uniformity in medical applications. | Polishing to Ra < 1 nm (SCD) and Ra < 5 nm (Inch-size PCD). |
| Surface Modification | Internal metalization services for creating custom contacts or bonding layers on diamond substrates. | Au, Pt, Pd, Ti, W, Cu metalization available. |
Engineering Support
Section titled âEngineering SupportâThe successful control of hydrophilicity and zeta potential relies heavily on precise material selection and plasma parameters. 6CCVDâs in-house PhD team specializes in the physical and chemical properties of CVD diamond and can assist with material selection for similar Biomimetic Surface Engineering and Advanced Plasma Processing projects.
We provide consultation on:
- Optimizing diamond substrate orientation and doping levels (e.g., BDD concentration) for specific electrochemical or surface modification goals.
- Designing custom diamond components (e.g., plasma reactor windows, high-power electrodes) that require extreme purity and durability.
- Selecting the appropriate diamond grade (SCD vs. PCD) based on required thermal, optical, or mechanical performance.
Call to Action: For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Medical tubing includes artificial vascular grafts and catheters, each has a different purpose of use, but they both need to hydrophilize the lumen surface. Diamond-like carbon (DLC) is a dry coating technology, and its surface can be easily modified with hydrophilic functional groups. AC high-voltage plasma chemical vapor deposition has been developed for DLC deposition on the inner surface of small-diameter long tubes. In addition, oxygen plasma treatment of the DLC-deposited surface has been performed to enhance the hydrophilicity of the tube lumen and to inhibit biofilm adhesion in urinary catheters. However, the oxygen plasma treatment using silicone as the base material had only a slight inhibitory effect on biofilm adhesion, with a water contact angle of 104.4° for the DLC film and 90.6° for the DLC film, compared with oxygen plasma treatment, with an average value of 119.5° for the blank film. Recently, a new ammonia plasma treatment method has been developed, and an ultra-hydrophilic water contact angle of nearly 10° has been achieved with polyurethan (PU) as the base material. Furthermore, the zeta potential was found to be negative in oxygen plasma treatment and positive in ammonia plasma treatment, indicating that the hydrophilicity, and surface potential can be arbitrarily controlled by combining these plasmas, thereby achieving surface properties suitable for various applications.