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This article focuses on the formation of the surface tension torque (STT) phenomenon close to the dry-line boundary layer during evaporation of the liquid phase of a solution casted shape-anisotropic nanoparticle suspension (here, cellulose nanowhisker (CNW)) or dissolved polymer (here, polyvinyl alcohol (PVA)) and its effects on self-assembly of the cellulose nanocrystals and polymer chains. The results confirm that the STT tends to align both the CNWs and the PVA chains tangential to the dry-line boundary layer. By careful control of the advancement of the dry-line, achieving special linear and curved patterns of both the CNWs and the PVA chains proportional to the mold position and geometry is possible. The STT phenomenon is explained and simplified in terms of a physical model. Understanding of the STT phenomenon and its effects on the alignment and self-assembly of the CNWs and PVA chains is necessary especially when achieving alignment using a modulated external magnetic or electric field is desired. The STT is safe, inexpensive, easy, and efficient, and can be a good alternative to the magnetic and electric field orientation methods.

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In this study, wet bacterial cellulose (BC) with a water content of more than 98% was utilized as a novel scaffold to design bioanodes for microbial fuel cells (MFCs). At first, unmodified wet BC was used a bioanode. Then a simple in situ synthesis of polypyrrole (PPYR) at various pyrrole concentrations was subsequently performed on the BC‘s fibers to generate the novel bioanodes. Characterization of the BC‐PPYR nanobiocomposites was conducted by using ATR‐FTIR, XRD, and FESEM. The performance of the nanobiocomposites was studied in a MFC system by using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and polarization curves. A power density of 136 mW/m2 and a current density of 662 mA/m2 were found for BC‐PPYR, which are superior to those of graphite (1 mW/m2 and 9 mA/m2, respectively). The results were attributed to a good adhesion of bacterial cells to the fibrous surface of BC, permanent capillary transfer of nutrients, the conductive content of hydrogel BC, and good conductivity and catalytic activity of PPYR in the nanocomposite.

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