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Highly elastic conductive polymeric MEMS

View Article: PubMed Central - PubMed

ABSTRACT

Polymeric structures with integrated, functional microelectrical mechanical systems (MEMS) elements are increasingly important in various applications such as biomedical systems or wearable smart devices. These applications require highly flexible and elastic polymers with good conductivity, which can be embedded into a matrix that undergoes large deformations. Conductive polydimethylsiloxane (PDMS) is a suitable candidate but is still challenging to fabricate. Conductivity is achieved by filling a nonconductive PDMS matrix with conductive particles. In this work, we present an approach that uses new mixing techniques to fabricate conductive PDMS with different fillers such as carbon black, silver particles, and multiwalled carbon nanotubes. Additionally, the electrical properties of all three composites are examined under continuous mechanical stress. Furthermore, we present a novel, low-cost, simple three-step molding process that transfers a micro patterned silicon master into a polystyrene (PS) polytetrafluoroethylene (PTFE) replica with improved release features. This PS/PTFE mold is used for subsequent structuring of conductive PDMS with high accuracy. The non sticking characteristics enable the fabrication of delicate structures using a very soft PDMS, which is usually hard to release from conventional molds. Moreover, the process can also be applied to polyurethanes and various other material combinations.

No MeSH data available.


Resistance-strain measurement for a 200 μm thin layer of Ag-PDMS. Different elongation cycles are shown, starting with cycle 2 after the first preload cycle.
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Figure 7: Resistance-strain measurement for a 200 μm thin layer of Ag-PDMS. Different elongation cycles are shown, starting with cycle 2 after the first preload cycle.

Mentions: Ag-PDMS. Ag-PDMS shows a behavior contrary to the ones observed for C-PDMS and MWCNT-PDMS. As displayed in figure 7, the resistance increases with each cycle of lengthening and changes by six orders of magnitude within 2500 cycles, beginning at at a distance of 33 mm leading to a conductivity of Sm−1. The resistance after preloading is . After 2500 elongation cycles, a resistance of was measured at 0% strain, thus being advanced by a factor of compared to the resistance measured after the preload cycle. Even though the material exhibits the highest conductivity at the beginning, it starts to fail after a few hundred elongation cycles. Its lack of reliability makes it unsuitable for use as sensor or actuator material. Besides that, the resistance of Ag-PDMS decreases with applied strain in a non linear manner. The material shows an increasing hysteresis with each consecutive cycle, leading to a hysteresis that stretches over almost two orders of magnitude for the cycle recorded after 2500 stretch- and-release cycles.


Highly elastic conductive polymeric MEMS
Resistance-strain measurement for a 200 μm thin layer of Ag-PDMS. Different elongation cycles are shown, starting with cycle 2 after the first preload cycle.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5036488&req=5

Figure 7: Resistance-strain measurement for a 200 μm thin layer of Ag-PDMS. Different elongation cycles are shown, starting with cycle 2 after the first preload cycle.
Mentions: Ag-PDMS. Ag-PDMS shows a behavior contrary to the ones observed for C-PDMS and MWCNT-PDMS. As displayed in figure 7, the resistance increases with each cycle of lengthening and changes by six orders of magnitude within 2500 cycles, beginning at at a distance of 33 mm leading to a conductivity of Sm−1. The resistance after preloading is . After 2500 elongation cycles, a resistance of was measured at 0% strain, thus being advanced by a factor of compared to the resistance measured after the preload cycle. Even though the material exhibits the highest conductivity at the beginning, it starts to fail after a few hundred elongation cycles. Its lack of reliability makes it unsuitable for use as sensor or actuator material. Besides that, the resistance of Ag-PDMS decreases with applied strain in a non linear manner. The material shows an increasing hysteresis with each consecutive cycle, leading to a hysteresis that stretches over almost two orders of magnitude for the cycle recorded after 2500 stretch- and-release cycles.

View Article: PubMed Central - PubMed

ABSTRACT

Polymeric structures with integrated, functional microelectrical mechanical systems (MEMS) elements are increasingly important in various applications such as biomedical systems or wearable smart devices. These applications require highly flexible and elastic polymers with good conductivity, which can be embedded into a matrix that undergoes large deformations. Conductive polydimethylsiloxane (PDMS) is a suitable candidate but is still challenging to fabricate. Conductivity is achieved by filling a nonconductive PDMS matrix with conductive particles. In this work, we present an approach that uses new mixing techniques to fabricate conductive PDMS with different fillers such as carbon black, silver particles, and multiwalled carbon nanotubes. Additionally, the electrical properties of all three composites are examined under continuous mechanical stress. Furthermore, we present a novel, low-cost, simple three-step molding process that transfers a micro patterned silicon master into a polystyrene (PS) polytetrafluoroethylene (PTFE) replica with improved release features. This PS/PTFE mold is used for subsequent structuring of conductive PDMS with high accuracy. The non sticking characteristics enable the fabrication of delicate structures using a very soft PDMS, which is usually hard to release from conventional molds. Moreover, the process can also be applied to polyurethanes and various other material combinations.

No MeSH data available.