Development of piezoresistive PDMS/MWCNT foam nanocomposite sensor with ultrahigh flexibility and compressibility

Abstract

Polymer foam nanocomposites attract great interest in many wide ranges of biomedical and healthcare monitoring applications. In this study, we investigated the effect of porosity and multi-walled carbon nanotube (MWCNT) content on the piezoresistivity, sensitivity, and mechanical properties of Polydimethylsiloxane (PDMS)/MWCNT foam nanocomposite. The foam nanocomposites were fabricated by particulate leaching method and their electrical and mechanical characteristics were investigated using the different porosity levels (60% and 70%) and different conductive nanofiller contents (0.5 wt.% and 1 wt.%). The foam nanocomposites with 0.5 wt.% MWCNT content and 60% porosity possessed higher pressure sensitivity, higher gage factor, and lower electrical hysteresis along with higher mechanical properties. Moreover, fabricated PDMS/MWCNT foam nanocomposite demonstrated high flexibility, high compressibility, and high recoverability in addition to limited mechanical hysteresis (less than 3%) with a large dynamic sensing range. Contrary to the existing foam nanocomposite samples in the literature, PDMS/MWCNT foam nanocomposites withstood higher pressure ranges (3.5–5 MPa) at limited thickness (average 2.3 mm) without experiencing noticeable macroscopic damage.

Mechanical characterization of multifunctional highly porous carbon nanotube‐reinforced foams

“…In the second step, the cryo‐fractured cross‐sections were then sputter‐coated with gold. [ 67 ] A transmission electron microscope (TEM, Hitachi H7500, Center of Neurobiology of Stress at the University of Toronto Scarborough) was used to observe MWCNT dispersion in the polymer matrix. For TEM sample preparation, initially, using a razor, specimens were chopped into small triangle pieces.…”

“…In the next step, the particulate leaching technique was initiated to proceed with the foaming part. [67,68] For this purpose, citric acid particles were manually added to the mixture and mixed to obtain a homogeneous composite. The weight of citric acid particles was measured to meet 3:2, 7:3, and 4:1 (citric acid to PDMS) mass ratios to make samples with 60%, 70%, and 80% voids, respectively.…”

Development of High-Sensitivity Piezoresistive Sensors Based on Highly Breathable Spacer Fabric with TPU/PPy/PDA Coating

“…Piezoresistive sensors are mainly constructed using thin-film and three-dimensional structures. Among those, thin-film piezoresistive sensors are usually made by coating elastic media such as polydimethylsiloxane (PDMS) [ 12 , 13 ], thermoplastic polyurethane (TPU) [ 14 , 15 ], Ecoflex [ 16 , 17 ], polymethyl methacrylate (PMMA) [ 18 , 19 ], polyethylene terephthalate (PET) [ 2 ], and cyclic olefin copolymer (COC) [ 20 ] as the substrate material. Montazerian et al [ 12 ], Ghahramani et al [ 13 ], Kumar et al [ 14 ], and He et al [ 17 ] used flexible polymers such as PDMS and TPU as substrates and coated them with conductive chopped carbon fiber (CCF), multi-walled carbon nanotubes (MWCNTs) and polypyrrole (PPy).…”

“…Among those, thin-film piezoresistive sensors are usually made by coating elastic media such as polydimethylsiloxane (PDMS) [ 12 , 13 ], thermoplastic polyurethane (TPU) [ 14 , 15 ], Ecoflex [ 16 , 17 ], polymethyl methacrylate (PMMA) [ 18 , 19 ], polyethylene terephthalate (PET) [ 2 ], and cyclic olefin copolymer (COC) [ 20 ] as the substrate material. Montazerian et al [ 12 ], Ghahramani et al [ 13 ], Kumar et al [ 14 ], and He et al [ 17 ] used flexible polymers such as PDMS and TPU as substrates and coated them with conductive chopped carbon fiber (CCF), multi-walled carbon nanotubes (MWCNTs) and polypyrrole (PPy). Flexible pressure sensors were prepared, and the measurement accuracy of the sensors could reach about 20 kPa −1 for medical health monitoring and wearable electronics.…”