Biocompatibility of Al2O3-Doped Diamond-like Carbon Laparoscope Coatings

At a Glance

Metadata	Details
Publication Date	2025-04-07
Journal	Coatings
Authors	Russell L. Leonard, Amj Bull, Fan Xue, Christopher P. Haycook, Sharon K. Gray
Institutions	University of Tennessee at Knoxville, Vanderbilt University
Citations	2
Analysis	Full AI Review Included

Technical Analysis and Documentation: Al₂O₃-Doped DLC Coatings for Biomedical Optics

Executive Summary

This documentation analyzes the synthesis and characterization of aluminum oxide-doped Diamond-Like Carbon (DLC) thin films for transparent, antifogging, and biocompatible coatings, positioning 6CCVD’s MPCVD diamond materials as the superior platform for replicating and advancing this research.

Application Validation: The study successfully synthesized Al₂O₃-doped DLC films via Pulsed Laser Deposition (PLD) for use on laparoscopic lenses, addressing critical issues of fogging and contamination in minimally invasive surgery.
Optimal Performance: Films doped at 17.5% Al₂O₃ demonstrated the best combination of properties, achieving high optical transparency (up to 98% transmission) and maximum surface energy (70 mN/m).
Hydrophilicity Achievement: The coatings exhibited high hydrophilicity, with water contact angles reduced from 32° (as-made) to less than 8° following argon plasma cleaning, confirming antifogging potential.
Biocompatibility Confirmed: The films showed excellent biostability (40 weeks in Simulated Body Fluid) and hemocompatibility, with no measurable ATP release from blood platelets, suggesting a low risk of coagulation-related adverse events.
Wear Resistance: Wear depth improved significantly at higher doping levels (20% and 25% Al₂O₃), demonstrating the potential for robust, scratch-resistant medical optics.
6CCVD Advantage: While the paper used amorphous DLC, 6CCVD offers high-purity, optical-grade Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD) as superior, intrinsically stable, and highly transparent substrates for next-generation biomedical coatings.

Technical Specifications

The following hard data points were extracted from the research paper, focusing on the optimal 17.5% Al₂O₃-doped film performance.

Parameter	Value	Unit	Context
Deposition Method	PLD	N/A	Pulsed Laser Deposition (ArF excimer laser, 193 nm)
Optimal Dopant Concentration	17.5	%	Al₂O₃ laser pulses on target (70,000 pulses)
Total Laser Pulses	400,000	N/A	Constant for all doped samples
Laser Fluence	4.1	J/cm²	Incident at 45°
Deposition Pressure	< 4.0 x 10^-4	Pa	High vacuum environment
Film Thickness (17.5% Doped)	37.4	nm	Measured via white-light interferometry
Maximum Optical Transmission	Up to 98	%	Across the visible spectrum (400-800 nm)
Minimum Water Contact Angle (As-made)	32	°	Achieved at 17.5% Al₂O₃ doping
Minimum Water Contact Angle (Plasma-cleaned)	< 8	°	Measured within 60 min of Ar plasma treatment
Maximum Surface Energy	70	mN/m	Achieved at 17.5% Al₂O₃ doping (Polar component driven)
RMS Surface Roughness (17.5% Doped)	10.0	nm	Measured via AFM
Hemocompatibility (ATP Release Limit)	< 0.01	nmol	Below instrument sensitivity limit (60 min exposure to PRP)
Biostability Test Duration	40	weeks	Immersion in Simulated Body Fluid (SBF)

Key Methodologies

The DLC films were synthesized using Pulsed Laser Deposition (PLD) under high vacuum conditions.

Substrate Preparation: 500 µm thick Corning 7980 fused silica substrates were cleaned sequentially via ultrasonic baths (acetone, methanol), ultrapure water rinse, followed by 2 min immersion in Piranha solution (H₂SO₄:H₂O₂ 1:1 v/v).
Target Composition: A multicomponent PLD target composed of semiconductor-grade graphite and Al₂O₃ was used, with axial rotation to ensure precise laser interaction.
Deposition Parameters: An ArF excimer laser (193 nm, 5 ns pulse duration) was used at a repetition rate of 100 Hz. The laser fluence was maintained at 4.1 J/cm².
Dopant Control: The total number of laser pulses was held constant at 400,000, while the percentage of pulses directed at the Al₂O₃ target was varied from 0% to 25% to control dopant concentration.
Surface Treatment: Selected samples underwent argon plasma cleaning for 3 min at medium radio-frequency (RF) power to assess temporary enhancement of hydrophilicity.
Characterization:
- Optical: Spectrophotometry (400-800 nm) for transmission and attenuation coefficient calculation.
- Surface: Contact angle measurements (ultrapure water, benzyl alcohol) for surface energy calculation (Fowkes method) and Atomic Force Microscopy (AFM) for RMS roughness.
- Mechanical: Hysitron TI 980 Triboindenter with a diamond Berkovich tip (100 µN load) for wear depth analysis.
- Biological: CellTiter-Glo assays (NIH/3T3 cells) for cytotoxicity and quantification of Adenosine Triphosphate (ATP) release from Platelet-Rich Plasma (PRP) for hemocompatibility.

6CCVD Solutions & Capabilities

The research demonstrates the viability of diamond-based coatings for advanced biomedical optics. 6CCVD specializes in high-purity MPCVD diamond, offering materials and customization capabilities that surpass the performance and scalability limitations of amorphous DLC films produced by PLD.

Research Requirement	6CCVD Material Recommendation	6CCVD Capability & Value Proposition
High Transparency & Biocompatibility	Optical Grade Single Crystal Diamond (SCD)	SCD offers superior intrinsic transparency and chemical inertness compared to amorphous DLC, ensuring maximum light transmission and long-term biostability in demanding surgical environments.
Large-Area Antifogging Optics	High-Purity Polycrystalline Diamond (PCD)	We provide PCD plates and wafers up to 125 mm in diameter, enabling the scalable production of large-format endoscope windows and optical components required for mass manufacturing.
Ultra-Thin Film Deposition	SCD/PCD Thin Films (0.1 µm minimum)	While the paper used 30-45 nm DLC, 6CCVD can provide ultra-thin, high-quality MPCVD diamond films starting at 0.1 µm (100 nm), offering a robust, crystalline foundation for subsequent surface functionalization (e.g., hydrophilic doping or plasma treatment).
Precision Surface Finish	Advanced Polishing Services	Achieving low contact angles requires minimal surface defects. We guarantee ultra-low roughness: Ra < 1 nm for SCD and Ra < 5 nm for inch-size PCD, critical for high-performance optical clarity.
Custom Doping/Functionalization	Boron-Doped Diamond (BDD) & Custom Metalization	6CCVD offers BDD, which can be engineered for specific electrochemical properties or surface energy modification, providing an alternative, highly stable route to achieving hydrophilicity or integrating heating elements.
Device Integration	In-House Metalization (Ti, Pt, Au, Cu, W, Pd)	We provide custom metalization layers (e.g., Ti/Pt/Au) directly onto the diamond surface, facilitating integration into complex medical devices, including the application of resistive heating elements mentioned in the paper to actively prevent fogging.

Engineering Support

6CCVD’s in-house PhD team provides expert consultation on material selection, surface preparation, and integration strategies. We specialize in tailoring MPCVD diamond properties—including thickness (up to 500 µm SCD/PCD), doping levels, and surface finish—to meet the stringent requirements of transparent biomedical optics and antifogging applications. We ensure global delivery with DDU default shipping, and DDP options available upon request.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Laparoscopic lens fogging and contamination pose significant challenges, leading to a reduced surgical field of view. Intraoperative cleaning to address these issues extends the surgical duration and elevates the risk of surgical site infections. The authors propose that a hydrophilic diamond-like carbon (DLC) coating would effectively mitigate fogging and fouling, thereby eliminating the requirement for intraoperative cleaning, while the scratch-resistant nature of DLC would provide additional benefits. The present study investigates the efficacy of aluminum oxide (Al2O3) as a dopant in diamond-like carbon (DLC) films for antifogging applications. The authors hypothesized that adding oxygen to the DLC matrix would increase surface energy by increased hydrogen bonding, resulting in a highly hydrophilic coating. Varying dopant concentrations were tested to observe their effects on hydrophilicity, transparency, biocompatibility, and wear properties. The doped films displayed a notable improvement in transparency throughout the visible spectrum. Plasma-cleaned samples demonstrated a substantial reduction in contact angles, achieving values less than 8°. The biocompatibility of these films was analyzed with CellTiter-Glo assays; the films demonstrated statistically similar levels of cell viability when compared to the control media. The absence of adenosine triphosphate released by blood platelets in contact with the DLC coatings suggests in vivo hemocompatibility. These films, characterized by high transparency, biocompatibility, and biostability, could be valuable for biomedical applications necessitating transparent coatings.

Tech Support

Original Source

DOI: https://doi.org/10.3390/coatings15040437

References

2014 - National Trends in the Adoption of Laparoscopic Cholecystectomy over 7 Years in the United States and Impact of Laparoscopic Approaches Stratified by Age
2023 - Minimally Invasive Surgery in the United States, 2022: Understanding Its Value Using New Datasets [Crossref]
1997 - A brief history of endoscopy, laparoscopy, and laparoscopic surgery [Crossref]
2016 - Comparative analysis of techniques to prevent laparoscopic fogging [Crossref]
2003 - Does using a laparoscopic approach to cholecystectomy decrease the risk of surgical site infection? [Crossref]
2022 - Laparoscopic Lens Defogging: A Review of Methods to Maintain a Clear Operating Field [Crossref]
2017 - Visual Occlusion During Minimally Invasive Surgery: A Contemporary Review of Methods to Reduce Laparoscopic and Robotic Lens Fogging and Other Sources of Optical Loss [Crossref]
2022 - Effective cleaning of endoscopic lenses to achieve visual clarity for minimally invasive abdominopelvic surgery: A systematic review [Crossref]
2022 - Nano-Ceramic Coating: A Novel Idea to Reduce Laparoscope Lens Fogging—Experimental Study [Crossref]
2023 - Biocompatibility of antifogging SiO-doped Diamond-Like carbon laparoscope coatings [Crossref]