Novel Electrically Conductive Porous PDMS/Carbon Nanofiber Composites for Deformable Strain Sensors and Conductors

Abstract

Highly flexible and deformable electrically conductive materials are vital for the emerging field of wearable electronics. To address the challenge of flexible materials with a relatively high electrical conductivity and a high elastic limit, we report a new and facile method to prepare porous polydimethylsiloxane/carbon nanofiber composites (denoted by p-PDMS/CNF). This method involves using sugar particles coated with carbon nanofibers (CNFs) as the templates. The resulting three-dimensional porous nanocomposites, with the CNFs embedded in the PDMS pore walls, exhibit a greatly increased failure strain (up to ∼94%) compared to that of the solid, neat PDMS (∼48%). The piezoresistive response observed under cyclic tension indicates that the unique microstructure provides the new nanocomposites with excellent durability. The electrical conductivity and the gauge factor of this new nanocomposite can be tuned by changing the content of the CNFs. The electrical conductivity increases, while the gauge factor decreases, upon increasing the content of CNFs. The gauge factor of the newly developed sensors can be adjusted from approximately 1.0 to 6.5, and the nanocomposites show stable piezoresistive performance with fast response time and good linearity in ln(R/R) versus ln(L/L) up to ∼70% strain. The tunable sensitivity and conductivity endow these highly stretchable nanocomposites with considerable potential for use as flexible strain sensors for monitoring the movement of human joints (where a relatively high gauge factor is needed) and also as flexible conductors for wearable electronics (where a relatively low gauge factor is required).

Highly Uniform and Low Hysteresis Piezoresistive Pressure Sensors Based on Chemical Grafting of Polypyrrole on Elastomer Template with Uniform Pore Size

“…Figure b shows Δ R / R 0 versus pressure curves of 10 sensors prepared using our uniform porous structure (i.e., uniform pore size and arrangement). Figure c shows Δ R / R 0 versus pressure curves of 10 sensors prepared using random pore‐based structure, using sugar cubes as template (randomly shaped and sized pores) 12b. Figure d shows SEM images of the sensors corresponding to Figure b (i.e., uniform porous structure) and Figure e are SEM images of the sensors corresponding to Figure c (i.e., random pore‐based structure).…”

“…Porous structures, in particular, was utilized in various pressure sensors due to their facile fabrication process and scalability. Porous structure can be fabricated either by filling a 3D template such as sugar, nickel foam with an elastomer and subsequently etching away the template, or by mixing aqueous and oil solutions to form an emulsion and removing the solvents 4b,14…”

Advances and Future Perspectives in 4D Bioprinting

“…A recent example showed coupling of electronics and sensor technology for monitoring physical activities in the body using bioengineered systems. [117] Future works would provide precise control on function of 4D bioprinted constructs in vivo in a minimally invasive manner. These works will open new ways for follow-up and care of implanted devices, tissues or organs in a personalized way.…”

Stretchable and compressible strain sensors for gait monitoring constructed using carbon nanotube/graphene composite

“…The growing demands in highly stretchable and deformable materials for use in human−machine interfaces [1] and human motion detectors [2] have motivated the development of highly sensitive stretchable strain and pressure sensors with high strain tolerance. Several stretchable strain sensors have been prepared using nanomaterials coupled with stretchable polymers [3][4][5][6][7][8][9]. Stretchable polymers such as poly (3, 4-ethylenedioxythophene) doped with poly (styrene sulfonic acid) (PEDOT:PSS) [3], thermoplastic polyurethane (TPU) [4], natural rubber [5], low density polyethylene (LDPE) [6], polydimethylsiloxane (PDMS) [7,8], and polyurethane (PU) [9] are generally selected as flexible matrix composites.…”