Preparation of Thermoplastic Polyurethane/Multi-Walled Carbon Nanotubes Composite Foam with High Resilience Performance via Fused Filament Fabrication and CO2 Foaming Technique

Wearable flexible sensors with high sensitivity and wide detection range are applied in motion detection, medical diagnostic result and other fields, but poor resilience and hysteresis remain a challenge. In this study, a high-resilience foam sensor was prepared through a combination of additive manufacturing and green physical foaming method. The conductive filaments were prepared by using MWCNTs-modified TPU by the physical method of melt blending. Samples were prefabricated using the FFF printer and then saturated with CO2 in an autoclave before being removed and heated to foam. The composite foam effectively reduced residual strain, demonstrating the high resilience of the 3D-printed composite materials with a foam porous structure. The residual strain of the sample before foaming was >6% after a single cycle, and then gradually increased. The residual strain of the foamed samples is less than 5%. In addition, composite foam has high sensitivity and can monitor subtle pressure changes (0~40 kPa). The sensing performance of the composite foam was evaluated, and the current signal remained stable under different loading rates and small compression strains (2~5%). By using this highly resilient conductive composite material, a hierarchical shoe insole was designed that successfully detected human walking and running movements.

[1]  Shuqiang Peng,et al.  Mechanical exfoliation assisted with carbon nanospheres to prepare a few-layer graphene for flexible strain sensor , 2022, Applied Surface Science.

[2]  Jianlei Wang,et al.  Progress of Polymer-Based Thermally Conductive Materials by Fused Filament Fabrication: A Comprehensive Review , 2022, Polymers.

[3]  Jianlei Wang,et al.  Progress in the Preparation, Properties, and Applications of PLA and Its Composite Microporous Materials by Supercritical CO2: A Review from 2020 to 2022 , 2022, Polymers.

[4]  H. Xiang,et al.  Electromechanical Performance of Strain Sensors Based on Viscoelastic Conductive Composite Polymer Fibers. , 2022, ACS applied materials & interfaces.

[5]  D. Xiang,et al.  Flexible Strain Sensors with Enhanced Sensing Performance Prepared from Biaxially Stretched Carbon Nanotube/Thermoplastic Polyurethane Nanocomposites , 2022, ACS Applied Electronic Materials.

[6]  Jianlei Wang,et al.  Facile Fabrication of Highly Sensitive Thermoplastic Polyurethane Sensors with Surface- and Interface-Impregnated 3D Conductive Networks. , 2022, ACS applied materials & interfaces.

[7]  Yutian Zhu,et al.  Highly-stretchable porous thermoplastic polyurethane/carbon nanotubes composites as a multimodal sensor , 2022, Carbon.

[8]  N. Abbas,et al.  Electrical Stability and Piezoresistive Sensing Performance of High Strain-Range Ultra-Stretchable CNT-Embedded Sensors , 2022, Polymers.

[9]  Qiuquan Guo,et al.  Tailoring of Photocurable Ionogel toward High Resilience and Low Hysteresis 3D Printed Versatile Porous Flexible Sensor , 2022, Chemical Engineering Journal.

[10]  Jianlei Wang,et al.  Rapid Carbon Dioxide Foaming of 3D Printed Thermoplastic Polyurethane Elastomers , 2022, ACS Applied Polymer Materials.

[11]  Chul B. Park,et al.  A comprehensive review of cell structure variation and general rules for polymer microcellular foams , 2022, Chemical Engineering Journal.

[12]  Guoqun Zhao,et al.  Nanocellular TPU composite foams achieved by stretch-assisted microcellular foaming with low-pressure gaseous CO2 as blowing agent , 2021, Journal of CO2 Utilization.

[13]  D. Jang,et al.  Design of a highly flexible and sensitive multi-functional polymeric sensor incorporating CNTs and carbonyl iron powder , 2021 .

[14]  Bin Hu,et al.  Development of microcellular thermoplastic polyurethane honeycombs with tailored elasticity and energy absorption via CO2 foaming , 2021 .

[15]  Chul B. Park,et al.  A review on physical foaming of thermoplastic and vulcanized elastomers , 2021, Polymer Reviews.

[16]  Haodong Liu,et al.  3D Printed Flexible Strain Sensors: From Printing to Devices and Signals , 2021, Advanced materials.

[17]  Shuai Guo,et al.  Study on the forming and sensing properties of laser-sintered TPU/CNT composites for plantar pressure sensors , 2021, The International Journal of Advanced Manufacturing Technology.

[18]  Lixin Wu,et al.  Tailored and Highly Stretchable Sensor Prepared by Crosslinking an Enhanced 3D Printed UV‐Curable Sacrificial Mold , 2020, Advanced Functional Materials.

[19]  Yang Yang,et al.  Carbon foams: 3D porous carbon materials holding immense potential , 2020 .

[20]  W. Fang,et al.  High-strength, flexible and cycling-stable piezo-resistive polymeric foams derived from thermoplastic polyurethane and multi-wall carbon nanotubes , 2020 .

[21]  A. Bahramian,et al.  A Comprehensive Review on Carbon-Based Polymer Nanocomposite Foams as Electromagnetic Interference Shields and Piezoresistive Sensors , 2020 .

[22]  Changki Mo,et al.  3D printed conductive thermoplastic polyurethane/carbon nanotube composites for capacitive and piezoresistive sensing in soft pneumatic actuators , 2020 .

[23]  N. Vidakis,et al.  3D Printed Thermoelectric Polyurethane/Multiwalled Carbon Nanotube Nanocomposites: A Novel Approach towards the Fabrication of Flexible and Stretchable Organic Thermoelectrics , 2020, Materials.

[24]  Chun H. Wang,et al.  Direct 3D Printing of Highly Anisotropic, Flexible, Constriction-Resistive Sensors for Multidirectional Proprioception in Soft Robots. , 2020, ACS applied materials & interfaces.

[25]  Q. Fu,et al.  Plasma modification of PU foam for piezoresistive sensor with high sensitivity, mechanical properties and long-term stability , 2020 .

[26]  Yuan Zhang,et al.  Mechanical–Microstructure Relationship and Cellular Failure Mechanism of Silicone Rubber Foam by the Cell Microstructure Designed in Supercritical CO2 , 2019, The Journal of Physical Chemistry C.

[27]  Ajay Giri Prakash Kottapalli,et al.  Ultralightweight and 3D Squeezable Graphene-Polydimethylsiloxane Composite Foams as Piezoresistive Sensors , 2019, ACS applied materials & interfaces.

[28]  Kai Huang,et al.  Three-dimensional printing of a tunable graphene-based elastomer for strain sensors with ultrahigh sensitivity , 2019, Carbon.

[29]  Richard S. Trask,et al.  Compressive behaviour of 3D printed thermoplastic polyurethane honeycombs with graded densities , 2019, Materials & Design.

[30]  J. Christ,et al.  Bidirectional and Stretchable Piezoresistive Sensors Enabled by Multimaterial 3D Printing of Carbon Nanotube/Thermoplastic Polyurethane Nanocomposites , 2018, Polymers.

[31]  Z. Pan,et al.  Flexible strain sensors fabricated using carbon-based nanomaterials: A review , 2018, Current Opinion in Solid State and Materials Science.

[32]  Weimin Bao,et al.  Three-Dimensional Interfacial Stress Sensor Based on Graphene Foam , 2018, IEEE Sensors Journal.

[33]  D. Xiang,et al.  Facile fabrication and performance of robust polymer/carbon nanotube coated spandex fibers for strain sensing , 2018, Composites Part A: Applied Science and Manufacturing.

[34]  Chul B. Park,et al.  Lightweight, super-elastic, and thermal-sound insulation bio-based PEBA foams fabricated by high-pressure foam injection molding with mold-opening , 2018, European Polymer Journal.

[35]  Changyu Shen,et al.  Flexible and Lightweight Pressure Sensor Based on Carbon Nanotube/Thermoplastic Polyurethane-Aligned Conductive Foam with Superior Compressibility and Stability. , 2017, ACS applied materials & interfaces.

[36]  Nahal Aliheidari,et al.  3D printed highly elastic strain sensors of multiwalled carbon nanotube/thermoplastic polyurethane nanocomposites , 2017 .

[37]  Maria Sabrina Sarto,et al.  A Flexible and Highly Sensitive Pressure Sensor Based on a PDMS Foam Coated with Graphene Nanoplatelets , 2016, Sensors.

[38]  Pierre Gilormini,et al.  Author manuscript, published in "European Polymer Journal (2009) 601-612" A review on the Mullins ’ effect , 2022 .