On the Synergistic Effect of Multi-Walled Carbon Nanotubes and Graphene Nanoplatelets to Enhance the Functional Properties of SLS 3D-Printed Elastomeric Structures
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-08-17 |
| Journal | Polymers |
| Authors | Gennaro Rollo, Alfredo Ronca, Pierfrancesco Cerruti, Xin Gan, Guoxia Fei |
| Institutions | Institute of Polymers, Composites and Biomaterials, Vilnius University |
| Citations | 37 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Advanced Functional Composites for Sensing and EMI Shielding
Section titled âTechnical Documentation & Analysis: Advanced Functional Composites for Sensing and EMI ShieldingâExecutive Summary
Section titled âExecutive SummaryâThis technical analysis reviews the fabrication and performance of 3D-printed elastomeric structures utilizing synergistic carbonaceous fillers (MWCNTs and Graphene) for high-sensitivity piezoresistive sensing and broadband electromagnetic interference (EMI) shielding.
- Core Achievement: Successful fabrication of highly porous Thermoplastic Polyurethane (TPU) structures via Selective Laser Sintering (SLS) using a synergistic 1 wt.% filler blend of Multi-Walled Carbon Nanotubes (MWCNTs) and Graphene Nanoplatelets (GE).
- Piezoresistive Performance: Demonstrated robust negative piezoresistivity, achieving a high absolute Gauge Factor (GF) of up to -13 at 8% compressive strain, confirming suitability for sensitive strain sensing applications.
- Thermal Stability: The synergistic MWCNT-GE filler blend significantly improved the thermal stability of the TPU matrix, shifting the first degradation onset temperature to 310 °C.
- Broadband EMI Shielding: The structures exhibited outstanding electromagnetic absorption, achieving coefficients ranging from 0.70 to 0.91 in the Ku-band (12-18 GHz).
- Extreme Frequency Capability: Near-perfect absorption (close to 1) was observed in the Terahertz (THz) range (300 GHz-1 THz), attributed to the multi-level porosity structure (nested âRussian dollâ porosity).
- Geometric Correlation: Gyroid (G) unit cell geometries consistently showed superior mechanical properties and lower electrical resistance compared to Diamond (D) geometries due to thicker internal trabeculae (1.360 mm vs. 1.040 mm for 60% porosity).
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Maximum Gauge Factor (GF) | -13 | N/A | At 8% compressive strain |
| Maximum Strain Tested | 8 | % | Cyclic loading/unloading |
| Porosity Range Investigated | 20 to 60 | % | D and G unit cells |
| Filler Concentration (Total) | 1 | wt.% | MWCNTs and GE |
| MWCNT:GE Ratio | 70:30 | wt/wt | Mixed filler system |
| Elastic Modulus (D20, MWCNT) | 15 | MPa | Highest modulus observed |
| Microwave Absorption (G20) | 0.70 to 0.91 | N/A | Ku-band (12-18 GHz), 10.6 mm thickness |
| THz Absorption (G20/G60) | Close to 1 | N/A | 300 GHz - 1 THz, 2 mm thickness |
| First Degradation Onset (TPU/MWCNT-GE) | 310 | °C | Improved thermal stability |
| Trabeculae Thickness (G60) | 1.360 ± 0.001 | mm | 30% thicker than D60 geometry |
| SLS Layer Thickness | 100 | ”m | Optimized sintering parameter |
| Part Bed Temperature | 85 | °C | Optimized sintering parameter |
Key Methodologies
Section titled âKey MethodologiesâThe functional structures were realized using Selective Laser Sintering (SLS) of custom-prepared nanocomposite powders.
- Nanocomposite Powder Preparation:
- Dispersion: MWCNTs (NANOCYL 7000) and Graphene (The Sixth Element) were pre-dispersed via wet ball milling (1 hour at 300 rpm) in anhydrous ethanol.
- Mixing: Thermoplastic Polyurethane (TPU) powder (Mophene3D T90A) was added to achieve a final filler content of 1 wt.%.
- Drying & Sieving: The mixture was dried in a vacuum oven at 70 °C for 24 hours and sieved (< 150 ”m). Silica powder was added to ensure optimal powder flowability for SLS.
- SLS Printing Parameters:
- The SLS process was performed on a lab-scale Sharebot-SnowWhite system.
- Laser Power: 14 W (set at 40% of maximum energy).
- Laser Scan Speed: 40,000 pps.
- Layer Thickness: 100 ”m.
- Piezoresistive Characterization:
- Samples (10 x 10 x 10 mmÂł) were subjected to 50 strain-controlled compression cycles (up to 8% strain) at 3 mm/min actuation rate.
- Electrical resistance was monitored using a 2-probe measurement method.
- Copper conductive tape was used as the electrode material on the top and bottom surfaces.
- Electromagnetic Characterization:
- Low Frequency (DC-1 MHz): Measured using a HP4284A LCR-meter on quasi-bulk samples (~5 x 5 x 3 mmÂł).
- Microwave (12-18 GHz): Measured using a Micran R4M vector analyzer and rectangular waveguide transmission line (10.6 mm thick samples).
- THz (300 GHz-1 THz): Measured using time-domain spectroscopy (T-Spec) on 2 mm thick plane-parallel slices.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe research demonstrates the critical need for materials with tailored electrical conductivity, mechanical stability, and precise geometric control for advanced sensing and electromagnetic applications. While this study focused on carbon-polymer composites, 6CCVD provides superior diamond materials that offer unmatched performance, stability, and thermal management for replicating or extending this research into high-performance regimes.
Applicable Materials
Section titled âApplicable MaterialsâTo achieve superior performance, stability, and thermal management in similar piezoresistive or high-frequency EM applications, 6CCVD recommends the following materials:
- Boron-Doped Diamond (BDD) Plates: Ideal for replacing carbon-polymer composites in piezoresistive sensing. BDD offers intrinsic, stable, and highly reproducible semiconducting properties, providing superior long-term stability and thermal robustness compared to the TPU/MWCNT-GE system.
- Optical Grade Single Crystal Diamond (SCD): Essential for high-power or extreme frequency (THz/GHz) applications. SCD possesses the highest known thermal conductivity and extremely low dielectric loss tangents, making it the optimal substrate or window material for high-efficiency EM devices.
- Polycrystalline Diamond (PCD) Substrates: Available in large formats (up to 125 mm diameter) for scaling up complex sensor arrays or large-area EMI shielding components where high thermal dissipation is required.
Customization Potential
Section titled âCustomization PotentialâThe success of the reported research relies heavily on precise geometry and reliable electrical contactâareas where 6CCVDâs custom fabrication capabilities provide a significant advantage.
| Research Requirement | 6CCVD Custom Capability | Benefit to Replication/Extension |
|---|---|---|
| Unique Dimensions (e.g., 10 x 10 x 10 mmÂł cubes) | Custom Dimensions & Laser Cutting: Plates and wafers available up to 125 mm (PCD). Custom shapes and precise geometries are achieved via advanced laser processing. | Enables rapid prototyping and production of application-specific sensor geometries (D or G unit cells). |
| Reliable Electrical Contact (Copper tape used, instability noted) | Integrated Metalization: In-house deposition of Au, Pt, Pd, Ti, W, and Cu. | Provides robust, high-adhesion electrodes directly onto the diamond surface, eliminating the electrical contact instability observed when using conductive tape. |
| Surface Quality (Critical for thin films/interfaces) | Precision Polishing: Achieved surface roughness (Ra) < 1 nm for SCD and < 5 nm for inch-size PCD. | Ensures optimal interface quality for subsequent thin-film deposition, bonding, or reliable sensor contact. |
| Thickness Control (0.1 ”m to 500 ”m films) | Precise Thickness Control: SCD and PCD films grown via MPCVD to exact specifications (0.1 ”m to 500 ”m). Substrates up to 10 mm thick. | Allows researchers to precisely tune material volume and electrical properties, critical for optimizing EM absorption characteristics (e.g., quarter-wavelength matching). |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house team of PhD material scientists and engineers specializes in optimizing MPCVD diamond for demanding applications. We offer comprehensive consultation for projects involving:
- High-Stability Piezoresistive Sensors: Assisting with BDD doping levels and geometry design for maximum Gauge Factor and long-term stability.
- Broadband EMI/THz Components: Material selection and design support for high-frequency electromagnetic windows, absorbers, and heat spreaders utilizing diamondâs unique dielectric and thermal properties.
- Custom Integration: Developing metalization schemes and surface preparation protocols tailored to specific device integration requirements.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Elastomer-based porous structures realized by selective laser sintering (SLS) are emerging as a new class of attractive multifunctional materials. Herein, a thermoplastic polyurethane (TPU) powder for SLS was modified by 1 wt.% multi-walled carbon nanotube (MWCNTs) or a mixture of MWCNTs and graphene (GE) nanoparticles (70/30 wt/wt) in order to investigate on both the synergistic effect provided by the two conductive nanostructured carbonaceous fillers and the correlation between formulation, morphology, and final properties of SLS printed porous structures. In detail, porous structures with a porosity ranging from 20% to 60% were designed using Diamond (D) and Gyroid (G) unit cells. Results showed that the carbonaceous fillers improve the thermal stability of the elastomeric matrix. Furthermore, the TPU/1 wt.% MWCNTs-GE-based porous structures exhibit excellent electrical conductivity and mechanical strength. In particular, all porous structures exhibit a robust negative piezoresistive behavior, as demonstrated from the gauge factor (GF) values that reach values of about â13 at 8% strain. Furthermore, the G20 porous structures (20% of porosity) exhibit microwave absorption coefficients ranging from 0.70 to 0.91 in the 12-18 GHz region and close to 1 at THz frequencies (300 GHz-1 THz). Results show that the simultaneous presence of MWCNTs and GE brings a significant enhancement of specific functional properties of the porous structures, which are proposed as potential actuators with relevant electro-magnetic interference (EMI) shielding properties.
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
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