Single Micro/Nanowire Pyroelectric Nanogenerators as Self-Powered Temperature Sensors

We demonstrated the first application of a pyroelectric nanogenerator as a self-powered sensor (or active sensor) for detecting a change in temperature. The device consists of a single lead zirconate titanate (PZT) micro/nanowire that is placed on a thin glass substrate and bonded at its two ends, and it is packaged by polydimethylsiloxane (PDMS). By using the device to touch a heat source, the output voltage linearly increases with an increasing rate of change in temperature. The response time and reset time of the fabricated sensor are about 0.9 and 3 s, respectively. The minimum detecting limit of the change in temperature is about 0.4 K at room temperature. The sensor can be used to detect the temperature of a finger tip. The electricity generated under a large change in temperature can light up a liquid crystal display (LCD)

Excluding Contact Electrification in Surface Potential Measurement Using Kelvin Probe Force Microscopy

Kelvin probe force microscopy (KPFM), a characterization method that could image surface potentials of materials at the nanoscale, has extensive applications in characterizing the electric and electronic properties of metal, semiconductor, and insulator materials. However, it requires deep understanding of the physics of the measuring process and being able to rule out factors that may cause artifacts to obtain accurate results. In the most commonly used dual-pass KPFM, the probe works in tapping mode to obtain surface topography information in a first pass before lifting to a certain height to measure the surface potential. In this paper, we have demonstrated that the tapping-mode topography scan pass during the typical dual-pass KPFM measurement may trigger contact electrification between the probe and the sample, which leads to a charged sample surface and thus can introduce a significant error to the surface potential measurement. Contact electrification will happen when the probe enters into the repulsive force regime of a tip–sample interaction, and this can be detected by the phase shift of the probe vibration. In addition, the influences of scanning parameters, sample properties, and the probe’s attributes have also been examined, in which lower free cantilever vibration amplitude, larger adhesion between the probe tip and the sample, and lower cantilever spring constant of the probe are less likely to trigger contact electrification. Finally, we have put forward a guideline to rationally decouple contact electrification from the surface potential measurement. They are decreasing the free amplitude, increasing the set-point amplitude, and using probes with a lower spring constant

Functional Electrical Stimulation by Nanogenerator with 58 V Output Voltage

We demonstrate a new type of integrated nanogenerator based on arrays of vertically aligned piezoelectric ZnO nanowires. The peak open-circuit voltage and short-circuit current reach a record high level of 58 V and 134 μA, respectively, with a maximum power density of 0.78 W/cm³. The electric output was directly applied to a sciatic nerve of a frog, inducing innervation of the nerve. Vibrant contraction of the frog’s gastrocnemius muscle is observed as a result of the instantaneous electric input from the nanogenerator

Piezotronic Effect in Solution-Grown p‑Type ZnO Nanowires and Films

Investigating the piezotronic effect in p-type piezoelectric semiconductor is critical for developing a complete piezotronic theory and designing/fabricating novel piezotronic applications with more complex functionality. Using a low temperature solution method, we were able to produce ultralong (up to 60 μm in length) Sb doped p-type ZnO nanowires on both rigid and flexible substrates. For the p-type nanowire field effect transistor, the on/off ratio, threshold voltage, mobility, and carrier concentration of 0.2% Sb-doped sample are found to be 10⁵, 2.1 V, 0.82 cm²·V^–1·s^–1, and 2.6 × 10¹⁷ cm^–3, respectively, and the corresponding values for 1% Sb doped samples are 10⁴, 2.0 V, 1.24 cm²·V^–1·s^–1, and 3.8 × 10¹⁷ cm^–3. We further investigated the universality of piezotronic effect in the as-synthesized Sb-doped p-type ZnO NWs and reported for the first time strain-gated piezotronic transistors as well as piezopotential-driven mechanical energy harvesting based on solution-grown p-type ZnO NWs. The results presented here broaden the scope of piezotronics and extend the framework for its potential applications in electronics, optoelectronics, smart MEMS/NEMS, and human-machine interfacing

Single-Electrode-Based Rotating Triboelectric Nanogenerator for Harvesting Energy from Tires

Rotational energy is abundant and widely available in our living environment. Harvesting ambient rotational energy has attracted great attention. In this work, we report a single-electrode-based rotating triboelectric nanogenerator (SR-TENG) for converting rotational energy into electric energy. The unique advantage of introducing the single-electrode TENG is to overcome the difficulty in making the connection in harvesting rotational energy such as from a moving and rotating tire/wheel. The fabricated device consists of a rotary acrylic disc with polytetrafluoroethylene (PTFE) blades and an Al electrode fixed on the base. The systematical experiments and theoretical simulations indicate that the asymmetric SR-TENGs exhibit much better output performances than those of the symmetric TENGs at the same rotation rates. The asymmetric SR-TENG with seven PTFE units at the rotation rate of 800 r/min can deliver a maximal output voltage of 55 V and a corresponding output power of 30 μW on a load of 100 MΩ, which can directly light up tens of red light-emitting diodes. The SR-TENG has been utilized to harvest mechanical energy from rotational motion of a bicycle wheel. Furthermore, we demonstrated that the SR-TENG can be applied to scavenge wind energy and as a self-powered wind speed sensor with a sensitivity of about 0.83 V/(m/s). This study further expands the operation principle of a single-electrode-based TENG and many potential applications of TENGs for scavenging ambient rotational energy and as a self-powered environment monitoring sensor

Triboelectric-Generator-Driven Pulse Electrodeposition for Micropatterning

By converting ambient energy into electricity, energy harvesting is capable of at least offsetting, or even replacing, the reliance of small portable electronics on traditional power supplies, such as batteries. Here we demonstrate a novel and simple generator with extremely low cost for efficiently harvesting mechanical energy that is typically present in the form of vibrations and random displacements/deformation. Owing to the coupling of contact charging and electrostatic induction, electric generation was achieved with a cycled process of contact and separation between two polymer films. A detailed theory is developed for understanding the proposed mechanism. The instantaneous electric power density reached as high as 31.2 mW/cm³ at a maximum open circuit voltage of 110 V. Furthermore, the generator was successfully used without electric storage as a direct power source for pulse electrodeposition (PED) of micro/nanocrystalline silver structure. The cathodic current efficiency reached up to 86.6%. Not only does this work present a new type of generator that is featured by simple fabrication, large electric output, excellent robustness, and extremely low cost, but also extends the application of energy-harvesting technology to the field of electrochemistry with further utilizations including, but not limited to, pollutant degradation, corrosion protection, and water splitting

Thermoelectric Nanogenerators Based on Single Sb-Doped ZnO Micro/Nanobelts

We demonstrate a thermoelectric nanogenerator (NG) made from a single Sb-doped ZnO micro/nanobelt that generates an output power of about 1.94 nW under a temperature difference of 30 K between the two electrodes. A single Sb-doped ZnO microbelt was bonded at its ends on a glass substrate as a NG, which can give an output voltage of 10 mV and an output current of 194 nA. The single Sb-doped ZnO microbelt shows a Seebeck coefficient of about −350 μV/K and a high power factor of about 3.2 × 10^–4 W/mK². The fabricated NG demonstrated its potential to work as a self-powered temperature sensor with a reset time of about 9 s

Toward Large-Scale Energy Harvesting by a Nanoparticle-Enhanced Triboelectric Nanogenerator

This article describes a simple, cost-effective, and scalable approach to fabricate a triboelectric nanogenerator (NG) with ultrahigh electric output. Triggered by commonly available ambient mechanical energy such as human footfalls, a NG with size smaller than a human palm can generate maximum short-circuit current of 2 mA, delivering instantaneous power output of 1.2 W to external load. The power output corresponds to an area power density of 313 W/m² and a volume power density of 54 268 W/m³ at an open-circuit voltage of ∼1200 V. An energy conversion efficiency of 14.9% has been achieved. The power was capable of instantaneously lighting up as many as 600 multicolor commercial LED bulbs. The record high power output for the NG is attributed to optimized structure, proper materials selection and nanoscale surface modification. This work demonstrated the practicability of using NG to harvest large-scale mechanical energy, such as footsteps, rolling wheels, wind power, and ocean waves

Toward Large-Scale Energy Harvesting by a Nanoparticle-Enhanced Triboelectric Nanogenerator

This article describes a simple, cost-effective, and scalable approach to fabricate a triboelectric nanogenerator (NG) with ultrahigh electric output. Triggered by commonly available ambient mechanical energy such as human footfalls, a NG with size smaller than a human palm can generate maximum short-circuit current of 2 mA, delivering instantaneous power output of 1.2 W to external load. The power output corresponds to an area power density of 313 W/m² and a volume power density of 54 268 W/m³ at an open-circuit voltage of ∼1200 V. An energy conversion efficiency of 14.9% has been achieved. The power was capable of instantaneously lighting up as many as 600 multicolor commercial LED bulbs. The record high power output for the NG is attributed to optimized structure, proper materials selection and nanoscale surface modification. This work demonstrated the practicability of using NG to harvest large-scale mechanical energy, such as footsteps, rolling wheels, wind power, and ocean waves

Toward Large-Scale Energy Harvesting by a Nanoparticle-Enhanced Triboelectric Nanogenerator

This article describes a simple, cost-effective, and scalable approach to fabricate a triboelectric nanogenerator (NG) with ultrahigh electric output. Triggered by commonly available ambient mechanical energy such as human footfalls, a NG with size smaller than a human palm can generate maximum short-circuit current of 2 mA, delivering instantaneous power output of 1.2 W to external load. The power output corresponds to an area power density of 313 W/m² and a volume power density of 54 268 W/m³ at an open-circuit voltage of ∼1200 V. An energy conversion efficiency of 14.9% has been achieved. The power was capable of instantaneously lighting up as many as 600 multicolor commercial LED bulbs. The record high power output for the NG is attributed to optimized structure, proper materials selection and nanoscale surface modification. This work demonstrated the practicability of using NG to harvest large-scale mechanical energy, such as footsteps, rolling wheels, wind power, and ocean waves