June 9, 2020 by admin 0 Comments

3D Printed Bioresponsive Devices with Selective Permeability Inspired by Eggshell Membrane for Effective Biochemical Conversion

Authors
Yale Jeon, Min Soo Jeon, Jongoh Shin, Sangrak Jin, Jonghun Yi, Seulgi Kang, Sun Chang Kim, Byung-Kwan Cho, Jung-Kul Lee, and Dong Rip Kim*
Abstract
Eggshell membrane has selective permeability that enables gas or liquid molecules to pass through while effectively preventing migration of microbial species. Herein, inspired by the architecture of the eggshell membrane, we employ three-dimensional (3D) printing techniques to realize bioresponsive devices with excellent selective permeability for effective biochemical conversion. The fabricated devices show 3D conductive carbon nanofiber membranes in which precultured microbial cells are controllably deployed. The resulting outcome provides excellent selective permeability between chemical and biological species, which enables acquisition of target responses generated by biological species confined within the device upon input signals. In addition, electrically conductive carbon nanofiber networks provide a platform for real-time monitoring of metabolism of microbial cells in the device. The suggested platform represents an effort to broaden microbial applications by constructing biologically programmed devices for desired responses enabled by designated deployment of engineered cells in a securely confined manner within enclosed membranes using 3D printing methods.

May 15, 2020 by admin 0 Comments

Exfoliated graphene/thermoplastic elastomer nanocomposites with improved wear properties for 3D printing

Authors
Hyerin Jeon a,b,1, Youn Kim b,1, Woong-Ryeol Yu a, Jea UkLee b
Abstract
Although three-dimensional (3D) thermoplastic elastomer printing has been studied, the unsatisfactory mechanical properties of 3D-printed elastomers, especially their substandard wear characteristics, make it difficult to use them in industrial products or processes. In this study, thermoplastic elastomer nanocomposites with improved wear properties were fabricated using thermoplastic polyether elastomer (TPEE), with surface-modified carbon black (CB), or electrochemically exfoliated graphene through multiple extrusion processes. The surface-modified CB/TPEE composite showed about four times more wear resistance and 26% improvement in tensile strength as compared to bare TPEE resin. The graphene/TPEE composite with only 1 wt% graphene exhibited an elevenfold increase in wear resistance and 43% improvement in the tensile strength owing to the high dispersibility and lubricating effect of the two-dimensional graphene filler. Graphene/TPEE composites were extruded into filaments for 3D printing. Three-dimensional printed products made from the nanocomposites have much higher wear resistance than 3D products of bare TPEE resin, demonstrating that graphene and TPEE nanocomposites are well suited for manufacturing a wide variety of complex electronic and mechanical components with excellent wear characteristics.