A new insight into the mechanical properties of nanobiofibers and vibrational behavior of atomic force microscope beam considering them as the samples

Abstract

Nowadays, the utilization and production of polymeric nanofibers are expanding rapidly due to their unique and exclusive properties. The current study examined silk fibroin nanofibers, poly-L lactic acid (PLLA), and polycaprolactone (PCL) as three widely-used biopolymers. In the first section, the mechanical properties of nanobiofibers, including elastic modulus as the first research variable, were investigated using atomic force microscopy (AFM)-based nanoindentation and tensile testing (through a universal testing machine). The results indicated that increasing the concentration of the biopolymer solution increased its elastic modulus. The total amount of elastic modulus for silk fibroin (SF), PCL, and PLLA nanofibers with random and aligned scaffold formats ranged from 1.207 MPa to 3.71 MPa. Based on the molecular weight and concentrations of the solutions, PLLA, PCL, and silk fibroin nanofibers yielded the highest elastic modulus, respectively. In addition, the elastic modulus was greater in an aligned scaffold as opposed to a random format and in retraction as opposed to an extended stroke. During the second section of the study, resonant frequencies as the second research variable and the amplitude of the FRF of the AFM beam's vertical movements using nanobiopolymers with various scaffolds as the samples were investigated theoretically (using the Finite Element Method [FEM]) and experimentally (using AFM). For the first to third modes, the resonant frequency of the AFM beam considering biopolymer nanofibers as samples varied from 12658.43 Hz to 241208.4 Hz. The results revealed that increasing the elastic modulus of the samples increases the resonant frequency. The mechanical and vibrational properties of nanofibers calculated by various methods were subsequently compared separately. Overall, the comparison indicated good agreement between the properties.

Keywords: Atomic force microscopy; Mechanical properties; Nanobiopolymer; Nanofiber; Resonant frequency.