Synchronous function of an ion-exchange polymer and carbon nanotube (CNT) leads to a splendid unipolar-stroke motion and superior actuation performance, in yarn artificial muscles. The ionic polymer proposed in this survey alters the zero potential to create a unipolar muscle (monotonical-stroke) behavior). This study is a great paradigm shift toward application of versatile systems and abundant, but highly functional materials for rehabilitation and healing purposes.
The availability of fiber conductors that can be stretched to large extents without significantly changing resistance or conductivity could enable the advances of elastic conductors as electronic interconnects, electronic skins, stretchable sensors, wearable systems, and medical robots. Therefore, the preparation of fiber conductors with high stretchability is crucial to the development of flexible electronic devices. This review summarizes the advances in constructing fiber conductors with an emphasis on recent developments of buckled structural design, fabrication methodologies, and strategies, with the ultimate goal of achieving good stability of resistance or conductivity at large strains. This review classifies the buckled fiber conductors into inner buckling and outer buckling, and related examples are summarized, providing a context that buckled fiber conductors are geared towards applications in electrical interconnects, wearable systems, and smart medical robotics. The present challenges in this area are critically evaluated and our perspectives for improving the performance of the buckled fiber conductors for future applications are presented.
Piezoelectric materials are highly desirable for wearable electronics and energy harvesting. Piezoelectric PVDF/ZnO composite nanofibers are particularly desirable for their nontoxicity, breathability, and flexibility. Here, we investigated three methods of fabricating PVDF and ZnO composite nanofibers aimed at optimum piezoelectric responses. It was found, (1) adding ZnO nanorod as fillers within the PVDF nanofiber did not improve piezoelectric response due to the fact that the process made the material more dielectric; (2) ZnO nanorods on the PVDF surface increased the power output due to the combined effects of piezoelectricity of ZnO nanorods as well as the triboelectric response of the increased surface roughness; (3) electrospraying pre-synthesized ZnO nanorods on PVDF nanofibers resulted in the highest piezoelectric response due to the combined effect of the greater piezoelectricity of aligned ZnO nanorods and PVDF nanofibers, and larger triboelectric response from increased surface roughness.
Two azobenzene compounds, Disperse Red 1 (DR1) and 4-aminoazobenzene (Aazo), were separately linked to poly(acrylic acid) (PAA) side chains to form PAA-DR1 and PAA-Aazo, which were then associated with poly(ethylene oxide) (PEO) to produce hydrogen-bonded polymer complex fibers. After UV irradiation, the initial modulus and yielding strength of PAA-Aazo/PEO fiber were both increased tremendously, while the mechanical properties of PAA-DR1/PEO fiber only slightly changed. After drawn and dried in vacuum, PAA-DR1/PEO and PAA-Aazo/PEO fibers with an extended length exhibited a contraction of 20% and 25% under UV irradiation, showing potential for photo-actuation.
Conducting fibers with improved properties and functionalities are needed for diverse applications. Here we report the fabrication of core/shell conductive Dacron fibers by dip-coating method through originating from multi-walled carbon nanotubes (MWCNTs) coated on polyester fibers. The annealing process was conducted to enhance interaction between the conductive shell and polyester core as well as within the MWCNTs network. The properties of two kinds of MWCNTs dispersions and the electrical properties of conductive fibers were studied, respectively. The results show that both MWCNTs-polyurethane resin (MWCNTs-WPU) dispersion and MWCNTs-acrylic resin (MWCNTs-PAA) dispersion present a typical characteristic of pseudo-plastic fluid and an excellent wetting ability to polyester fibers. The ultimate tensile stress and elongation at break for the MWCNTs-PAA coated fiber are 261 MPa and 25.43%. The ultimate tensile stress and the elongation at break are both increasing with the increasing of MWCNTs contents, due to the strong interface bonding ability between the conductive shell and polyester core and strengthen the MWCNTs network. The electrical resistance of the obtained fibers can be controlled in the range from 732 to 30 Ω/cm by changing MWCNTs content, dipping times and annealing temperature. It was found that it is able to light a LED. All results suggest that the conductive fibers embody a good synergy effect of carbon nanotubes and polymers. Therefore, the fabricated conductive fibers have a widely prospect for being applied in the field of flexible electronics.
Detection of circulating tumor cells (CTCs) plays an important role in early diagnosis of cancer and personalized therapy. However, isolated CTCs, especially those captured by positive sorting methods, are difficult to culture in subsequent assays because the cells have to be labeled or attached to a substrate for separation. In this study, a negative sorting method has been developed for isolation of CTCs through a microfluidic platform integrated with streptavidin-functionalized electrospun polylactic-co-glycolic acid nanofibers. Through the specific biotin-streptavidin interaction, the device is able to sort out biotinylated anti-CD45 antibody-labeled white blood cells (WBCs) and enrich A549 human cancer cells from the blood or CTCs from patient suffering non-small cell lung cancer. We demonstrate that the WBC capture efficiency is as high as 97.0%, and the recovery rate of cancer cells reaches up to 97.5%. CTCs are enumerated from blood samples of patients suffering lung carcinoma. The number of CTCs increased with the progression of NCCN TNM stages and showed statistically significant difference between stage I and later stages. These results suggest that the integrated negative sorting device is promising to be used for diagnosis of cancer.