ICMCTF 2026 Session MD1-1-MoM: Coatings and Surfaces for Medical Devices: Mechanical, Corrosion, Tribocorrosion, and Surface Processing I

Sarin (isopropyl methyl phosphono fluoridate) is an organophosphate ester with high potency as nerve agent, which is extremely dangerous and rapidly attacks the nervous system of human body and makes them incapable in merely few seconds. As direct experimentation with Sarin is highly restricted, dimethyl methylphosphonate (DMMP) serves as a widely accepted safe simulant to explore this biologically-hazardous molecule better.

Through this study, fabrication of active sensing surfaces on chromatography paper strips is discussed, which are coated with gold nanoparticles (AuNPs) and 3-aminopropyltriethoxysilane (APTES) via a dip-and-dry coating technique. These strips enable a rapid and selective chemical response towards DMMP, thereby changing their effective dielectric response.Such a strip is superimposed on a resonant sensor, which is a complementary split-ring resonator (CSRR) operating at 428 MHz. The compact and highly sensitive CSRR sensor is designed on an FR4 substrate with copper metallization, which are excited using RF signal to create electromagnetic field around. The coated strips superimposition on the sensor bed not only augments the electromagnetic near-field confinement of the sensor but also modifies the resonant frequency and signal power as the surface chemistry changes with DMMP interactions. Our studies show detection in the range of 100 to 500 ppm of DMMP, wherein the sensor demonstrates a frequency shift from 10 MHz to 18 MHz and a power variation of 1.98 dB to 4.7 dB. The CSRR–AuNPs–APTES hybrid system highlights the interdisciplinary relevance of surface-engineered coatings in biomedical and environmental sensing, offering potential solutions for nerve gas detections. A smart diagnostic platform with real-time monitoring for healthcare diagnostics is demonstrated.

Keywords- Organophosphorus compounds, Complementary split-ring resonator (CSRR), Surface engineering, Paper-based biosensor, RF sensor, Biocompatibility, Environmental monitoring, Real-time detection platform

This study investigates the synergistic interactions between fretting wear and electrochemical crevice corrosion in diamond-like carbon (DLC) coating systems on AISI 316L substrate under physiologically representative conditions. Particular emphasis is placed on understanding how albumin influences fretting–corrosion mechanisms, given their critical role in many engineering and biomedical environments. A combined experimental methodology is employed, integrating micro-mechanical characterisation (instrumented indentation and scratch testing) with fretting experiments employing in-situ electrochemical characterisation to assess coating durability, damage initiation, and interfacial degradation. Electrochemical techniques, including open-circuit potential monitoring, potentiodynamic polarisation, and electrochemical impedance spectroscopy, are applied in situ during fretting to capture the evolving interaction between mechanical and electrochemical degradation processes.

Fretting was replicated by applying micro-motion to the Al2O3 ball relative to the coated plate under a dead weight normal load. A maximum Hertzian contact pressure of 800 MPa was used for the tests, at a fretting displacement amplitude of 100 µm, giving a gross slip fretting regime. Each fretting test lasted 60 minutes resulting in 3600 cycles at a frequency of 1 Hz. Detailed surface and subsurface analyses using scanning electron microscopy, focused ion beam cross-sectioning, and energy-dispersive X-ray spectroscopy reveal progressive coating damage involving micro-cracking, interfacial delamination, and tribologically induced graphitisation of the DLC layer. Results demonstrate that fretting accelerates corrosion through mechanical disruption of the coating–substrate interface, while corrosion promotes further fretting damage via under-film attack and crack propagation, establishing a genuine fretting-corrosion synergy.

A mechanistic model is proposed in which mechanical defect initiation, electrochemical attack, and debris generation act in a feedback loop, driving progressive coating degradation. These insights highlight the importance of considering protein–surface interactions and combined degradation modes when designing DLC coatings for demanding fretting–corrosion service conditions in biomedical and engineering applications.