Summary In this study, we developed a multilayer thin‐film triboelectric nanogenerator (MT‐TENG) that incorporates a honeycomb‐patterned spacer fabricated via screen printing by using ultraviolet curable ink. The printed spacer, a thin polymer layer, and thin metal electrodes enable the formation of a single thin‐film structure. When force is applied to the thin‐film TENG, the honeycomb‐patterned spacer helps the polymer layer deform elastically through the opening of the pattern and contact the electrode. We implemented an MT‐TENG by stacking 3 30 mm × 30 mm × 1.4 mm TENG layers electrically connected in parallel. The electrical performances of the manufactured MT‐TENG with respect to the open‐circuit voltage and short‐circuit current were 11.45 V and 4.46 μA, respectively. The instantaneous output power density was 10.56 μW/cm3 (13.30 μW). In addition, an MT‐TENG shoe insole was fabricated to harvest energy from human walking. We demonstrated that the fabricated shoe insole could light up 9 commercial green light‐emitting diodes during walking to have an open‐circuit voltage of about 20 V.

The triboelectric nanogenerator (TENG) has become one of the strongest candidates for sustainable power sources. The power of a TENG depends on factors such as contact area, contact parallelism, contact force, and contact speed. In order to evaluate the performance of the TENG precisely and quantitatively, it is necessary to apply consistent experimental conditions and measurement processes. In this paper, we propose a test bed capable of adjusting the contact area and contact parallelism and measuring the contact force, contact speed, current, and voltage in real time. The test bed consists of a 2-axis planar stage, a 2-axis tilting stage, a 1-axis vertical stage, a 3-degree-of-freedom (DOF) force/torque sensor, a capacitive displacement sensor, and a voice coil actuator. The 3-DOF force/torque sensor can provide feedback on the degree of parallelism and contact area alignment as well as contact force. With the proposed test bed, the effects of parallelism error, contact area, contact force, and contact speed on the performance of contact-mode TENGs are quantitatively analyzed. This test bed is expected to be used for the quantitative analysis of contact-mode TENGs with various new structures and for comparison among different devices.

Open-path Fourier transform infrared spectrometry (OP/FT-IR) may improve the temporal and spatial resolution in air pollutant measurements compared to conventional sampling methods. However, a successful OP/FT-IR operation requires an experienced analyst to resolve chemical interference as well as to derive a suitable background spectrum. The present study aims at developing a systematic method of handling the OP/FT-IR derived spectra for the measurement of photochemical oxidants and volatile organic compounds (VOCs) in urban areas. A classical least-squares (CLS) method, the most frequently used regression method in OP/FT-IR, is modified to constrain all the analyzed chemical species concentrations within a physically reasonable range. This new CLS method, named constrained CLS, may save the effort of predetermining the chemical species to be analyzed. A new background spectrum generation method is also introduced to more efficiently handle chemical interferences. Finally, CLS is shown to be prone to propagating errors in the case that a few data points contain a significant amount of error. The LI-norm minimization method reduces this error propagation to considerably increase the stability compared to CLS. The presently developed analysis software based on these approaches is compared with the other conventional CLS method using an artificially made single-beam spectrum as well as a field single-beam spectrum.

A piezoelectric cantilever with an eccentrically connected wire-mass relay is proposed for extensive energy harvesting from broadband vibration responses. The relay mass is chosen to be much greater than that of the cantilever. The vibration source is magnified by the relay as a bending-swinging-torsional excitation to drive the cantilever. Thus, multiple vibration modes of the cantilever are effectively employed to enhance energy harvesting. A prototype device was developed and characterized. The results show that the proposed structure can generate much more electricity over a broader bandwidth than conventional structures.

The triboelectric nanogenerator (TENG) has been attracting attention for electronic devices and sensors consuming low power. Among the few operating modes of the TENG, the rotation-based TENG provides a more continuous and smoother output than the linear-motion-based TENG. To evaluate the output performance of the rotation-based TENG precisely and quantitatively, a test bed that adjusts the eccentricity error, tilt angle error, contact force, and rotational speed is proposed. The test bed includes a motor, torque sensor, 2-axis planar stage, 2-axis tilting stage, 1-axis vertical stage, 3-degree-of-freedom force/torque (3-DOF F/T) sensor, and voice coil actuator. With the proposed test bed, the effects of the eccentricity error, tilt angle error, contact force, and rotational speed on the electrical output performance of the rotation-based TENG are analyzed. The test bed is expected to be used for quantitative performance analysis and comparative study of various rotation-based TENGs, and it can help improve the performance and reliability of rotation-based TENGs.