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Anomalous tensile response of bacterial cellulose nanopaper at intermediate strain rates.

ABSTRACT: Nanocellulose network in the form of cellulose nanopaper is an important material structure and its time-dependent mechanical response is crucial in many of its potential applications. In this work, we report the influences of grammage and strain rate on the tensile response of bacterial cellulose (BC) nanopaper. BC nanopaper with grammages of 20, 40, 60 and 80 g m^-2 were tested in tension at strain rates ranging from 0.1% s^-1 to 50% s^-1. At strain rates [Formula: see text] 2.5% s^-1, both the tensile modulus and strength of the BC nanopapers stayed constant at?~?14 GPa and?~?120 MPa, respectively. At higher strain rates of 25% s^-1 and 50% s^-1 however, the tensile properties of the BC nanopapers decreased significantly. This observed anomalous tensile response of BC nanopaper is attributed to inertial effect, in which some of the curled BC nanofibres within the nanopaper structure do not have enough time to uncurl before failure at such high strain rates. Our measurements further showed that BC nanopaper showed little deformation under creep, with a secondary creep rate of only?~?10^-6 s^-1. This stems from the highly crystalline nature of BC, as well as the large number of contact or physical crosslinking points between adjacent BC nanofibres, further reducing the mobility of the BC nanofibres in the nanopaper structure.

SUBMITTER: Santmarti A

PROVIDER: S-EPMC7498453 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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Anomalous tensile response of bacterial cellulose nanopaper at intermediate strain rates.

Santmarti Alba A Liu Hon Wah HW Herrera Natalia N Lee Koon-Yang KY

Scientific reports 20200917 1

Nanocellulose network in the form of cellulose nanopaper is an important material structure and its time-dependent mechanical response is crucial in many of its potential applications. In this work, we report the influences of grammage and strain rate on the tensile response of bacterial cellulose (BC) nanopaper. BC nanopaper with grammages of 20, 40, 60 and 80 g m-2 were tested in tension at strain rates ranging from 0.1% s-1 to 50% s-1. At strain rates [Formula ...[more]

PMID: 32943686

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Project description:ObjectivesOrthodontic treatment in adult patients predisposed to mild or severe periodontal disease is challenging for orthodontists. Orthodontic malpractice or hyper-occlusal forces may aggravate periodontitis-induced destruction of periodontal tissues, but the specific mechanism remains unknown. In the present study, the combined effect of mechanical stress and tumor necrosis factor (TNF)-α on the inflammatory response in human periodontal ligament stromal cells (hPDLSCs) was investigated.Materials and methodshPDLSCs from 5 healthy donors were treated with TNF-α and/or subjected to cyclic tensile strain (CTS) of 6% or 12% elongation with 0.1 Hz for 6- and 24 h. The gene expression of interleukin (IL)-6, IL-8 and cell adhesion molecules VCAM and ICAM was analyzed by qPCR. The protein levels of IL-6 and IL-8 in conditioned media was measured by ELISA. The surface expression of VCAM-1 and ICAM-1 was quantified by immunostaining followed by flow cytometry analysis.ResultsTNF-α-induced IL-6 gene and protein expression was inhibited by CTS, whereas TNF-α-induced IL-8 expression was decreased at mRNA expression level but enhanced at the protein level in a magnitude-dependent manner. CTS downregulated the gene expression of VCAM-1 and ICAM-1 under TNF-α stimulation, but the downregulation of the surface expression analyzed by flow cytometry was observed chiefly for VCAM-1.ConclusionsOur findings show that mechanical force differentially regulates TNF-α-induced expression of inflammatory mediators and adhesion molecules at the early stage of force application. The effect of cyclic tensile strain is complex and could be either anti-inflammatory or pro-inflammatory depending on the type of pro-inflammatory mediators and force magnitude.Clinical relevanceOrthodontic forces regulate the inflammatory mediators of periodontitis. The underlying mechanism may have significant implications for future strategies of combined periodontal and orthodontic treatment.

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Anomalous tensile response of bacterial cellulose nanopaper at intermediate strain rates.

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Anomalous tensile response of bacterial cellulose nanopaper at intermediate strain rates.

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