TLT: How did you decide to pursue a career in the field of tribology?
Kumar: My interest in tribology developed gradually during my postgraduate studies and research work in mechanical engineering. I became particularly fascinated by how surface interactions, friction, wear and lubrication govern the performance and reliability of engineering systems across multiple scales. During my MTech and later doctoral research, I realized that tribology is a highly interdisciplinary field that integrates materials science, mechanics, manufacturing and surface engineering while maintaining strong industrial relevance. The opportunity to work on advanced materials, surface coatings and sustainable lubrication systems has particularly motivated me to pursue this field further.  

TLT: What is your advice to someone applying for the MSCA fellowship?
Kumar: Regarding the MSCA Fellowship, I believe one of the most important aspects is building a strong and original research proposal with clear scientific impact, novelty and international relevance. Applicants should carefully identify a host institution and supervisor whose expertise strongly aligns with their proposed research objectives. It is equally important to demonstrate how the fellowship will contribute to both scientific advancement and personal career development. A well-structured work plan, realistic methodology, strong publication record and clear communication of expected outcomes significantly improve the chances of success. I would also strongly recommend starting the proposal preparation early, discussing ideas with mentors and collaborators, and paying close attention to the excellence, impact and implementation sections, which are the core evaluation criteria of the MSCA Fellowship.

TLT: How is macro-scale and nano-scale tribology crucial to understanding materials properties at different scales, and what unique insights each scale provides?
Kumar: Macro-scale tribology explains the overall, engineering-level behavior of materials—such as friction, wear rate, heat generation and failure in real components like bearings or brakes—using continuum contact mechanics and bulk material response.

Nano-scale tribology reveals the fundamental origins of these behaviors by focusing on atomic and asperity-level interactions, including adhesion, surface energy, tribo-chemical reactions and stick–slip motion at real contact points.

Together, they are crucial because macro-scale performance is the collective outcome of countless nano-scale contact events, meaning nano-scale mechanisms determine why a material behaves the way it does at the engineering scale.

TLT: What are the biggest tribological challenges in using magnesium alloys, in practical applications, and how can research address those challenges?
Kumar: Magnesium alloys face major tribological limitations in practical applications, mainly due to their low hardness, poor wear resistance and strong tendency for adhesive wear and galling, especially against steel counterparts. Their surface oxide films are weak and non-protective, leading to rapid breakdown during sliding, unstable friction behavior and severe material transfer. In addition, magnesium shows poor high-temperature stability because of thermal softening, and its performance is further degraded by corrosion–wear synergy, where corrosion accelerates material loss and wear exposes fresh reactive surfaces. Research addresses these challenges through alloying with elements like Al, Zn and rare earths to improve hardness and tribo-film stability, surface engineering techniques such as PEO/MAO coatings and DLC layers to reduce adhesion and wear and composite approaches using ceramic reinforcements or solid lubricants to enhance load-bearing capacity. Grain refinement techniques like severe plastic deformation also improve wear resistance by increasing hardness, while tribo-film engineering focuses on forming stable, low-shear transfer layers during sliding. Overall, current research is moving from bulk property enhancement toward designing stable and protective surface-controlled tribological behavior for reliable magnesium alloy applications.

TLT: Could you discuss the development of novel conductive contact materials for MEMS/NEMS devices and what innovative approaches can be taken to improve their performance and reliability?
Kumar: Novel conductive contact materials for MEMS/NEMS aim to overcome issues like high contact resistance, wear, stiction and oxidation that limit reliability in traditional materials. Research is focusing on robust alternatives like ruthenium and other noble metals, carbon-based materials and diamond-like carbon coatings to improve wear resistance and electrical stability. At the same time, surface engineering approaches such as nano-texturing, self-assembled monolayers and engineered tribo-layers are being used to control adhesion and stabilize contact behavior. Device-level strategies like controlled contact force, protective packaging and hybrid or self-healing interfaces (e.g., liquid metals) further enhance durability. Overall, the trend is toward multi-functional, nano-engineered contact systems that integrate material, surface and structural design for reliable long-term operation.

TLT: What are some of the most promising future directions in high entropy alloy tribology, and what are the current roadblocks to their wider adoption in tribological applications?
Kumar: High-entropy alloy (HEA) tribology is promising for extreme environments due to their high hardness, thermal stability and ability to form adaptive tribo-oxide layers that can reduce wear and friction. Future directions include designing HEAs with self-lubricating compositions, developing nano-structured and gradient alloys for improved wear resistance, using HEA coatings for high-temperature applications and applying machine learning for accelerated alloy design. However, wider adoption is limited by challenges such as the complex and limited understood composition–property relationships, high material and processing costs, difficulty in achieving consistent microstructures and the lack of long-term, real-service tribological data.

You can reach Deepak Kumar at dkumar@iipe.ac.in or d.kumar1@imperial.ac.uk.