Self-Powered Signal Transduction of Ion-Selective Electrodes to an Electronic Paper Display

Self-Powered Potentiometric Sensor with Relational Operation Function to Capture Concentration Excursions

Self-powered potentiometric sensors spontaneously respond to activity changes of target species without the need for an external power source. Here, a self-powered potentiometric sensing approach is described that may store concentration perturbations that occur before the sensor readout through a combination of capacitors and diodes. Two channels, termed "more than" and "less than" operators, are utilized as memory modules in the sensor circuit to record positive and negative concentration excursions, respectively. Each channel is constructed with a capacitor-diode pair in which each diode is connected to a capacitor in the opposite direction to prevent unwanted capacitor discharge. With this design, only potential variations that agree with the polarity of the diode may pass and be stored in the capacitor. A limitation of the principle is that the conductivity of the diode is very small if the voltage across it diminishes over time as it approaches the equilibrium value. To address this, the forward voltage is increased by about 1 V by switching from an initial Ag/AgCl reference electrode (RE) to a Zn/Zn2+ element. The device may be used to monitor whether a concentration excursion has occurred in the time leading up to the signal readout in a semiquantitative manner. The approach also differentiates pH excursions of different durations (20, 40, 60 min). As an example, four different pH excursions of 20 min duration were successfully distinguished in river water samples with amplitudes of 1 to 4 pH units relative to the case without pH perturbation.

Pinecone derived hierarchical carbon nanostructure as a transducer in a solid-state ion-selective electrode for in vivo analysis of calcium ion

Monitoring extracellular calcium ion (Ca2+) chemical signals in neurons is crucial for tracking physiological and pathological changes associated with brain diseases in live animals. Potentiometry based solid-state ion-selective electrodes (ISEs) with the assist of functional carbon nanomaterials as ideal solid-contact layer could realize the potential response for in vitro and in vivo analysis. Herein, we employ a kind of biomass derived porous carbon as a transducing layer to prompt efficient ion to electron transduction while stabilizes the potential drift. The eco-friendly porous carbon after activation (APB) displays a high specific area with inherit macropores, micropores, and large specific capacitance. When employed as transducer in ISEs, a stable potential response, minimized potential drift can be obtained. Benefiting from these excellent properties, a solid-state Ca2+ selective carbon fiber electrodes (CFEs) with a sandwich structure is constructed and employed for real time sensing of Ca2+ under electrical stimulation. This study presents a new approach to develop sustainable and versatile transducers in solid-state ISEs, a crucial way for in vivo sensing.

Self-Powered Potentiometric Sensor Based on a Passive Signal Amplifier with Electronic Paper Display

Self-powered potentiometric sensors are attractive because of their simple operation, low cost, fast response, and ability to be integrated with electronic components. Self-powered potentiometric sensors that give a direct colorimetric output are especially interesting, because no power supply is needed, which dramatically reduces waste. Recently reported work from our group using an electronic paper display, however, exhibits limitations, because the visualization of small pH changes is difficult. A self-powered ion-selective potentiometric sensor is introduced here that may amplify the e-paper pixel sensitivity by improving the self-powered circuit. The voltage is amplified by changing the circuit from incorporating parallel to incorporating serial capacitors. With three such capacitors, a greatly improved sensitivity is observed, amplifying the absorbance 3-fold. A portable device is realized that changes the position of the capacitors from parallel to serial through a simple mechanical sliding action. As a result, the pH information on the sample is more easily visualized with a pH uncertainty of about 0.1 when comparing the e-paper output to a color card.

Distance-Based Self-Powered Signal Transduction of Ion-Selective Electrodes to an Electronic Paper Display Array

In this article, we report on the first distance-based readout self-powered potentiometric sensor. The approach is considered more user-friendly for detection by the naked eye and is less prone to optical interferences compared with a direct observation of the pixel darkening. pH-selective electrodes were chosen as a model system to demonstrate the principle in which seven bar-shaped pixels connected in series on one e-paper share one common ground. By connecting each of the pixels serially to capacitors of different capacitances, the fraction of the measurement cell voltage loaded onto the pixels becomes controllable. Consequently, the pixels give different gray values when powered by the same ion-selective electrode (ISE). As a result, the pH information on the sample is visualized as a distance-based signal and the dependence between the capacitance and 1/K (the reciprocal slope in the relationship between absorbance and pH) was constructed. In the current system, a 1 μF capacitance difference changes the value of 1/K by 4.18. With the current setup, the pH accuracy is about 0.5 when comparing the e-paper output to a color card.

Electrospun Cellulose Nanocrystals Reinforced Flexible Sensing Paper for Triboelectric Energy Harvesting and Dynamic Self-Powered Tactile Perception

The technical synergy between flexible sensing paper and triboelectric nanogenerator (TENG) in the next stage of artificial intelligence Internet of Things engineering makes the development of intelligent sensing paper with triboelectric function very attractive. Therefore, it is extremely urgent to explore functional papers that are more suitable for triboelectric sensing. Here, a cellulose nanocrystals (CNCs) reinforced PVDF hybrid paper (CPHP) is developed by electrospinning technology. Benefitting from the unique effects of CNCs, CPHP forms a solid cross-linked network among fibers and obtains a high-strength (25 MPa) paper-like state and high surface roughness. Meanwhile, CNCs also improve the triboelectrification effect of CPHP by assisting the PVDF matrix to form more electroactive phases (96% share) and a higher relative permittivity (17.9). The CPHP-based TENG with single electrode configuration demonstrates good output performance (open-circuit voltage of 116 V, short-circuit current of 2.2 µA and power density of 91 mW m-2 ) and ultrahigh pressure-sensitivity response (3.95 mV Pa-1 ), which endows CPHP with reliable power supply and sensing capability. More importantly, the CPHP-based flexible self-powered tactile sensor with TENG array exhibits multifunctional applications in imitation Morse code compilation, tactile track recognition, and game character control, showing great prospects in the intelligent inductive device and human-machine interaction.

A Self-Powered Piezoelectric Nanofibrous Membrane as Wearable Tactile Sensor for Human Body Motion Monitoring and Recognition

Wearable sensors have drawn vast interest for their convenience to be worn on body to monitor and track body movements or exercise activities in real time. However, wearable electronics rely on powering systems to function. Herein, a self-powered, porous, flexible, hydrophobic and breathable nanofibrous membrane based on electrospun polyvinylidene fluoride (PVDF) nanofiber has been developed as a tactile sensor with low-cost and simple fabrication for human body motion detection and recognition. Specifically, effects of multi-walled carbon nanotubes (CNT) and barium titanate (BTO) as additives to the fiber morphology as well as mechanical and dielectric properties of the piezoelectric nanofiber membrane were investigated. The fabricated BTO@PVDF piezoelectric nanogenerator (PENG) exhibits the high β-phase content and best overall electrical performances, thus selected for the flexible sensing device assembly. Meanwhile, the nanofibrous membrane demonstrated robust tactile sensing performance that the device exhibits durability over 12,000 loading test cycles, holds a fast response time of 82.7 ms, responds to a wide pressure range of 0-5 bar and shows a high relative sensitivity, especially in the small force range of 11.6 V/bar upon pressure applied perpendicular to the surface. Furthermore, when attached on human body, its unique fibrous and flexible structure offers the tactile sensor to present as a health care monitor in a self-powered manner by translating motions of different movements to electrical signals with various patterns or sequences.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s42765-023-00282-8.