4 research outputs found
Influences of Surface and Ionic Properties on Electricity Generation of an Active Transducer Driven by Water Motion
In
this Letter, we discuss the surface, ionic properties, and scale-up
potential of an active transducer that generated electricity from
natural water motion. When a liquid contacts a solid surface, an electrical
double layer (EDL) is always formed at the solid/liquid interface.
By modulating the EDL, the active transducer could generate a peak
voltage of ∼3 V and a peak power of ∼5 μW. Interestingly,
there were specific salinities of solution droplets that showed maximum
performance and different characteristics according to the ions’
nature. Analyzing the results macroscopically, we tried to figure
out the origins of the active transducing precipitated by ions dynamics.
Also, we demonstrated the scale-up potential for practical usage by
multiple electrode design
Efficient Colorimetric pH Sensor Based on Responsive Polymer–Quantum Dot Integrated Graphene Oxide
In this paper, we report the development of a versatile platform for a highly efficient and stable graphene oxide (GO)-based optical sensor that exhibits distinctive ratiometric color responses. To demonstrate the applicability of the platform, we fabricated a colorimetric, GO-based pH sensor that responds to a wide range of pH changes. Our sensing system is based on responsive polymer and quantum dot (QD) hybrids integrated on a single GO sheet (MQD-GO), with the GO providing an excellent signal-to-noise ratio and high dispersion stability in water. The photoluminescence emissions of the blue and orange color-emitting QDs (BQDs and OQDs) in MQD-GO can be controlled independently by different pH-responsive linkers of poly(acrylic acid) (PAA) (p<i>K</i><sub>a</sub> = 4.5) and poly(2-vinylpyridine) (P2VP) (p<i>K</i><sub>a</sub> = 3.0) that can tune the efficiencies of Förster resonance energy transfer from the BQDs to the GO and from the OQDs to the GO, respectively. As a result, the color of MQD-GO changes from orange to near-white to blue over a wide range of pH values. The detailed mechanism of the pH-dependent response of the MQD-GO sensor was elucidated by measurements of time-resolved fluorescence and dynamic light scattering. Furthermore, the MQD-GO sensor showed excellent reversibility and high dispersion stability in pure water, indicating that our system is an ideal platform for biological and environmental applications. Our colorimetric GO-based optical sensor can be expanded easily to various other multifunctional, GO-based sensors by using alternate stimuli-responsive polymers
Identification of Droplet-Flow-Induced Electric Energy on Electrolyte–Insulator–Semiconductor Structure
Recently,
various energy transducers driven by the relative motion
of solids and liquids have been demonstrated. However, in relation
to the energy transducer, a proper understanding of the dynamic behavior
of ions remains unclear. Moreover, the energy density is low for practical
usage mainly due to structural limitations, a lack of material development
stemming from the currently poor understanding of the mechanisms,
and the intermittently generated electricity given the characteristics
of the water motion (pulsed signals). Here, we verify a hypothesis
pertaining to the ion dynamics which govern the operation mechanism
of the transducer. In addition, we demonstrate enhanced energy transducer
to convert the mechanical energy of flowing water droplets into continuous
electrical energy using an electrolyte–insulator–semiconductor
structure as a device structure. The output power per droplet mass
and the ratio of generated electric energy to the kinetic energy of
water drops are 0.149<i>v</i><sup>2</sup> mW·g<sup>–1</sup>·m<sup>–2</sup>·s<sup>2</sup> and
29.8%, respectively, where <i>v</i> is the speed of the
water droplet
Fabric Active Transducer Stimulated by Water Motion for Self-Powered Wearable Device
The
recent trend of energy-harvesting devices is an adoption of fabric
materials with flexible and stretchable according to the increase
of wearable electronics. But it is a difficult process to form a core
structure of dielectric layer or electrode on fabric materials. In
particular, a fabric-based energy-harvesting device in contact with
water has not been studied, though there are many challenging issues
including insulation and water absorption in a harsh environment.
So we propose an effective method to obtain an electrical energy from
the water contact using our new fabric energy harvesting device. Our
water motion active transducer (WMAT) is designed to obtain electrical
energy from the variable capacitance through the movement and contact
of water droplet. In this paper, we succeeded in generating an electrical
energy with peak to peak power of 280 μW using a 30 μL
of water droplet with the fabric WMAT device of 70 mm × 50 mm
dimension. Furthermore, we specially carried out spray-coating and
transfer processes instead of the conventional spin-coating process
on fabric materials to overcome the limitation of its uneven morphology
and porous and deformable assembly