Qi Wang publishes the study on lubrication and delubrication of microgels in Food Hydrocolloids

Qi Wang (Visiting PhD Student, Zheizhang Gongshang University China) publishes his work titled "Lubrication and delubrication behaviour of micron-sized whey protein microgels" in Food Hydrocolloids. This study investigated how lubrication properties of whey protein microgels (WPM) can be altered by varying their sizes in the micron-scale and deformability. To decipher the lubrication mechanisms of WPM dispersions (3-48 vol %),  two tribological systems were tested i.e. conventional smooth substrate and novel biomimetic tongue-like surfaces. Findings demonstrate that the tribological performance of micron-sized microgel-based lubricants is governed not only by the particles’ physical attributes (e.g., size and deformability) but equally by the material properties of the contacting surfaces (smooth surface versus textured tongue papillae). Ball-on-smooth disc friction measurements demonstrated that entrainment of relatively non-deformable particles was mainly governed by the size ratio between the particles and the lubricant film thickness generated by hydrodynamic lift forces. The inclusion of hard WPM particles into a soft contact of similar wettability to that of human tongue exhibited a detrimental role in lubrication, with higher volume fraction of hard microgels leading to increased friction coefficients. Conversely, soft WPM display superior lubricity in ball-on-smooth disc setup, possibly due to microgel deformation and entrainment into the contact. The oral-mimetic tribo-system, however, is more sensitive to the presence of WPM in the contact region, with a delubrication effect observed even at the lowest volume fractions, irrespective of the size and deformability of WPMs. This behavior stems from the unique interfacial architecture between the spherical probe and papillae, which creates discrete lubricant reservoir that accommodate and interlock the WPMs and restrict their mobility within the contact surfaces, increasing frictional dissipation. Although sensory validation is lacking, the unique lubrication and delubrication behavior observed here may inspire rethinking of strategies for food, drug and oral care products development, when incorporating rigid micron-sized microgels particles that require interacting with texturized, soft bio-surfaces such as human tongue. The full text can be read in Food Hydrocolloids, Volume 172, Article No. 111908 https://doi.org/10.1016/j.foodhyd.2025.111908