Triboelectric nanogenerators, or TENGs, harvest ambient mechanical energies and convert them to electricity by coupling triboelectrification and field induction. The apparatus comprises a dielectric as an electron acceptor and a metal layer as an electron donor. These devices are low-cost, simple, and can use waste plastic materials, like snack chip food packaging, as the dielectric layer. Snack chip packaging uses a multilayer of metalized Biaxially Oriented Polypropylene to preserve the food quality. This study fabricated two vertical contact-separation modes, TENGs-cl and rf, using waste materials as an upper layer, while the opposite layer is made from aluminum foil. TENG-cl and TENG-rf could generate an output voltage of 699.0 Vpp and 1045.0 Vpp, respectively. TENG-cl and rf generated a power density of 4.0 mW m⁻² and 9.0 mW m⁻² from the rms voltage across the 60 MΩ load resistor. The output was significantly higher than previously reported devices using similar materials.

Philippine inland waters experience increasing pressures of nutrient enrichment and algal blooms which threaten water quality, biodiversity, and human health. Chlorophyll monitoring, the most critical indicator of algal biomass, plays a key role in eutrophication evaluation and identification of harmful algal blooms (HABs). Satellite and unmanned aerial vehicle (UAV)-based remote sensing technology provides large area chlorophyll-a mapping, with accuracy dependent on precise ground-truth measurements for calibration and validation. This paper presents the design and verification of a low-cost fluorescence spectrometer for potential in-situ chlorophyll-a measurement that supports geospatial benchmarking and the validation of remote sensing. The spectrometer consists of a Hamamatsu C12880MA mini spectrometer contained in a Raspberry Pi microcontroller with an LED-based excitation source to detect chlorophyll a fluorescence emission in Chlorella vulgaris samples. Laboratory tests compared the developed spectrometer with a commercial Ocean Optics fluorescence spectrometer, and with a high correlation between excitation spectra (R2 = 0.9304) and moderate correlation between emission spectra (R2 = 0.7269), validating that the system can detect chlorophyll-a fluorescence signals as relevant to the spectral bands used in satellite-based water quality indexes. Though proven under laboratory conditions, the low-cost, compact design provides for prospective field deployment for real-time monitoring. The built fluorescence spectrometer thus provides an emerging, scalable approach to ground-based spectral measurement, bridging laboratory instrumentation and geospatial remote sensing applications to improve the accuracy and temporal resolution of freshwater quality monitoring.

Background/Objectives: Dental biofilm formation on prosthetic materials contributes to oral diseases and material degradation. This pilot study evaluated the feasibility of combining time-domain optical coherence tomography (TD-OCT) and non-contact atomic force microscopy (NC-AFM) to characterize biofilm-associated optical and surface changes in dental prosthesis materials following antiseptic treatment. Methods: Acrylic resin, composite resin, and stainless-steel specimens were inoculated with Streptococcus mutans biofilms and exposed to water, Orahex, and Watsons mouthwash. TD-OCT was used to obtain extinction coefficient (EC) and optical thickness measurements, while NC-AFM was performed on Orahex-treated specimens to assess nanoscale surface morphology. EC distributions were analyzed descriptively from valid TD-OCT A-scans. Results: Within the examined specimens, EC distributions varied following biofilm formation and antiseptic treatment, with material-dependent responses. Composite resin exhibited the clearest reduction in EC following Watsons treatment, whereas acrylic resin and stainless-steel specimens showed more variable responses. Physical thickness remained relatively stable, while NC-AFM observations of the Orahex-treated specimens supported the TD-OCT findings by demonstrating corresponding surface morphological changes. Conclusions: This pilot study demonstrates the preliminary feasibility of integrating TD-OCT with NC-AFM for non-destructive evaluation of biofilm-associated optical and surface changes in dental prosthesis materials. The findings are descriptive and exploratory, highlighting the potential of TD-OCT for monitoring prosthetic materials while emphasizing the need for future studies incorporating independent biological replicates and complementary biological validation techniques.

Wireless triboelectric nanogenerators (TENGs) can power devices, detect oscillations, and transmit Morse code. We present TAP-C-TENG, the first to encode messages in tap code and decode them with a low-cost microcontroller. Made from recycled snack packaging, this vertical contact-separation TENG generates 1628 V and 192 µA at 3 Hz. Its pulses are processed by an ESP32-C3 microcontroller, which decodes messages sent via WebSocket to a web app, such as ”TENG" in real-time. The peak signal ranges from 2.0-2.5 V up to 100 cm, dropping to 0.7 V beyond 140 cm. Only the transmitter requires a battery.