This study reports
flexible nanocomposite-based piezoelectric nanogenerators
(PENGs) fabricated by dispersing various piezoelectric nanoparticles
(BaTiO3, ZnO, and PZT) and graphene nanopowder in a silicone
matrix. The results indicated that the PZT-based composites showed
superior performance in comparison to other ceramics. Subsequently,
practical application of PENGs was demonstrated by developing a fully
functioning shoe-insole nanogenerator (SING). The SING generated high
open-circuit voltage (∼27 V), short-circuit current (429.23
μA), and power density (402 mW/m2) under real-time
human walking. Moreover, a facile and inexpensive fabrication method
for efficient, skin-friendly, and highly stretchable biomechanical
piezoelectric sensors is also proposed. In this regard, multiwall
carbon nanotubes/silicone composite stretchable electrodes were prepared
to be compatible with the sensors. The electrodes displayed stability
even under high uniaxial elongation (100%), and the fabricated sensors
responded effectively to almost every joint movement. The results
suggested that the fabricated PENGs can be potentially used as self-powered
biomechanical energy harvesters/sensors in wearable electronics, haptic
sensing, or internet of human-related applications.
Fuzzy logic image analysis techniques were used to analyze three shades of blue (lavender blue, light blue, and dark blue) in dermoscopic images for melanoma detection. A logistic regression model provided up to 82.7% accuracy for melanoma discrimination for 866 images. With a support vector machines (SVM) classifier, lower accuracy was obtained for individual shades (79.9–80.1%) compared with up to 81.4% accuracy with multiple shades. All fuzzy blue logic alpha cuts scored higher than the crisp case. Fuzzy logic techniques applied to multiple shades of blue can assist in melanoma detection. These vector-based fuzzy logic techniques can be extended to other image analysis problems involving multiple colors or color shades.
Flexible electronic devices have gained significant interest due to their different potential applications. Herein, we report highly flexible, stretchable, and sensitive sensors made of sprayed CNT layer, sandwiched between two polymer layers. A facile fabrication process was employed in which the CNT solution was directly sprayed onto a patterned bottom polymer layer, above which a second polymer layer was casted to get a sandwiched composite structure. Varying amounts of CNT solution (i.e., 10, 25, 40, 70, and 100 mL) were sprayed to get conductive CNT layers of different thicknesses/densities. The physical characteristics of the conductive CNT layers were studied through SEM and optical images. The starting electrical resistance values (without strain) as well as the changes in electrical resistance against human body motions were monitored. The synthesized samples exhibited good response against finger and wrist bending. The conductivity of the samples increased with increase of CNT solution volume while the sensitivity followed the inverse relation, suggesting that the sensors with controlled sensitivity could be fabricated for targeted strain ranges using the proposed method.
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