Direct measurement of colloidal forces using an atomic force microscope

Direct measurements of non-ionic attraction and nanoscaled lubrication in biomimetic composites from nanofibrillated cellulose and modified carboxymethylated cellulose

“…Promising mechanical properties have been achieved, and there have been significant advances considering the composite preparation techniques; however, the focus has been on finding optimal mixing ratios, developing convenient upscalable methods, or characterizing the composite structure. 5, 10-15 45 Less attention has been paid to the interphase phenomena, although they are of pivotal importance for the control of the structures and the final properties. 9,16 Previous conclusions regarding beneficial interactions between soft and hard domains are, at first sight, contradicting.…”

“…By comparing symmetric 40 systems, where both cellulose surfaces were covered with CMCg-PEG, to asymmetric systems, where only one of the surfaces was covered, it was possible to understand the effect of CMC-g-PEG on the interactions at the fibril interfaces within the composite. The results are discussed in terms of the importance 45 of boundary lubrication, origin of attraction between the components, and the possible existence of sacrificial bonds and fibril pullout. The nano-scaled interfacial interactions were further related to the mechanical properties of macroscopic composites and we speculate on how these interfacial phenomena 50 contribute to crack propagation and toughening of composites.…”

“…45 The colloidal probes were prepared by gluing cellulose spheres with diameters in the range of 15-20 µm (determined with a Leica DM750 optical microscope) at the end of tipless CSC12 cantilevers (MikroMasch) with the help of a 5 micromanipulator (Narishige, Japan). An optical adhesive (Norland Products Inc., Cranbury, USA), cured under UV light, was used in the preparation of the cellulose colloidal probes.…”

“…The 40 dispersion was stirred overnight whereupon free-standing nanocomposite films were prepared by pressurized filtration and hot pressing for two hours as described previously. 27 Tensile tests were carried out with an Instron 4204 universal 45 tensile testing machine and Bluehill 2 program. The gauge length, load cell and crosshead speed were 30 mm, 100 N, and 0.5 mm min -1 , respectively.…”

Bioinspired lubricating films of cellulose nanofibrils and hyaluronic acid

“…The atomic force microscope, 5 in combination with the colloid probe technique, has proved to be very useful for the measurement of forces between surfaces at micro/nanoscale with high sensitivity. 23,24 In particular, this technique has been applied to analyze the forces between cellulose surfaces such as cellulose microspheres and CNF films, coated or not with different polymers. 2530 Friction forces between fibrils also play a very important role in the behavior of cellulose materials.…”