A Sustainable Free-Standing Triboelectric Nanogenerator Made of Flexible Composite Film for Brake Pattern Recognition in Automobiles.

In recent years, the automotive industry has made significant progress in integrating multifunctional sensors to improve vehicle performance, safety, and efficiency. As the number of integrated sensors keeps increasing, there is a growing interest in alternative energy sources. Specifically, self-powered sensor systems based on energy harvesting are drawing much attention, with a main focus on sustainability and reducing reliance on typical batteries. This paper demonstrates the use of triboelectric nanogenerators (TENGs) in a computer mouse for efficient energy harvesting and in automobile braking systems for safety applications using SrBi2Ta2O9 (SBTO) perovskite, blended PDMS composite operating in free-standing mode with an interdigitated patterned aluminum electrode. This self-powered sensor is capable of distinguishing between normal and abnormal braking patterns using digital signal processing techniques. It is noteworthy that the addition of 15% wt. of the SBTO in PDMS composite-based TENG delivered 13.5 V, 45 nA, and an output power of 0.98 µW. This new combination of energy harvesting and safety applications enables real-time monitoring and predictive maintenance in the automotive industry.

Effect of synthesis methodologies upon the photocatalytic performance of Bi0.5Na0.5TiO3 for pollutant degradation.

In the face of mounting environmental concerns, we must seek out innovative solutions for remediation. Using nanomaterials to degrade organic pollutants in water under ambient visible light holds great promise as a safe, cost-efficient, and effective approach to addressing pollution in our water bodies. The development of novel materials capable of such pollution degradation is desired to preserve the environment. In this study, Bi0.5Na0.5TiO3 (BNT) nanoparticles are synthesized through hydrothermal and solid-state routes, and their physicochemical properties are compared to assess their photocatalytic performance. The results of the characterization studies indicate that the hydrothermally synthesized nanoparticles outperformed the solid-state synthesized counterparts in terms of photocatalytic performance. The photocatalytic degradation of Rhodamine blue dye under ambient light exposure is examined at various dye concentrations and catalyst dosages. BNT nanoparticles demonstrated excellent photocatalytic properties, stability, and recyclability, making them a promising candidate for various photocatalytic applications. The findings of this study could pave the way for the development of sustainable and environmentally friendly photocatalytic technologies for water remediation.

Carbohydrate-protein interaction-based detection of pathogenic bacteria using a biodegradable self-powered biosensor.

Battery-free and biodegradable sensors can detect biological elements in remote areas. The triboelectric nanogenerator (TENG) can potentially eliminate the need for a battery by simply converting the abundant vibrations from nature or human motion into electricity. A biodegradable sensor system integrated with TENG to detect commonly found disease-causing bacteria (E. coli) in the environment is showcased herein. In this system, D-mannose functionalized 3D printed polylactic acid (PLA) with the brush-painted silver electrode was used to detect E. coli by a simple carbohydrate-protein interaction mechanism. The adsorption capacity of D-mannose is generally altered by varying the concentration of E. coli resulting in changes in resistance. Thus, the presented biosensor can detect bacterial concentrations by monitoring the output current. The PLA TENG generates an output of 70 V, 800 nA, and 22 nC, respectively. In addition, tap water and unpasteurized milk samples are tested for detecting bacteria, and the output is measured at 6 µA and 5 µA, respectively. Further, the biosensor was tested for biodegradability in soil compost by maintaining constant temperature and humidity. This study not only proposes an efficient and fast method for screening E. coli but also gives important insights into the ability to degrade and long-term reliability of TENG-based sensor platforms.

Sustainable Solutions for Oral Health Monitoring: Biowaste-Derived Triboelectric Nanogenerator.

Oral healthcare monitoring is a vital aspect of identifying and addressing oral dental problems including tooth decay, gum pain, and oral cancer. Day by day, healthcare facilities and regular checkups are becoming more costly and time-consuming. In this context, consumers are moving toward advanced technology, such as bite sensors, to obtain regular data about their occlusal chewing patterns and strength. The triboelectric nanogenerator (TENG) can potentially eliminate the need for a battery by simply converting abundant vibrations from nature or human motion into electrical energy. In this work, biomaterials are obtained from biowastes such as cellulose from wood waste, chitosan from crab shells, and gelatin from fish scales. All wastes are biodegradable, and our work aims at sustainability and waste hierarchy. The single electrode mode-based TENG was designed and fabricated using biodegradable poly(vinyl alcohol) (PVA)-biomaterial composites, rice paper as a substrate, and edible silver leaf as an electrode. The highest electrical output was obtained for PVA/chitosan 10 wt % composite-based TENG (PC10) of about 20 V, 200 nA, and 12 nC. The biomechanical energy harvesting was measured, and powering of LED was demonstrated using a PC10 TENG device. A biocompatible bite sensor based on the TENG was used to measure the biting force of a dummy teeth model to demonstrate its potential use in dental health applications. It indicates the promising future value of disposable oral medication devices without any invasive surgery or injection.

Bismuth sulfoiodide (BiSI) nanorods: synthesis, characterization, and photodetector application.

The nanorods of bismuth sulfoiodide (BiSI) were synthesized at relatively low temperature (393 K) through a wet chemical method. The crystalline one-dimensional (1D) structure of the BiSI nanorods was confirmed using high resolution transmission microscopy (HRTEM). The morphology and chemical composition of the material were examined by applying scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), respectively. The average diameter of 126(3) nm and length of 1.9(1) µm of the BiSI nanorods were determined. X-ray diffraction (XRD) revealed that prepared material consists of a major orthorhombic BiSI phase (87%) and a minor amount of hexagonal Bi13S18I2 phase (13%) with no presence of other residual phases. The direct energy band gap of 1.67(1)  eV was determined for BiSI film using diffuse reflectance spectroscopy (DRS). Two types of photodetectors were constructed from BiSI nanorods. The first one was traditional photoconductive device based on BiSI film on stiff glass substrate equipped with Au electrodes. An influence of light intensity on photocurrent response to monochromatic light (λ = 488 nm) illumination was studied at a constant bias voltage. The novel flexible photo-chargeable device was the second type of prepared photodetectors. It consisted of BiSI film and gel electrolyte layer sandwiched between polyethylene terephthalate (PET) substrates coated with indium tin oxide (ITO) electrodes. The flexible self-powered BiSI photodetector exhibited open-circuit photovoltage of 68 mV and short-circuit photocurrent density of 0.11 nA/cm2 under light illumination with intensity of 0.127 W/cm2. These results confirmed high potential of BiSI nanorods for use in self-powered photodetectors and photo-chargeable capacitors.

Graphene oxide decorated multi-frequency surface acoustic wave humidity sensor for hygienic applications.

This work presents the single-chip integration of a multi-frequency surface acoustic wave resonator (SAWR) based humidity sensor. Graphene oxide (GO), a humidity-sensing material, is integrated onto a confined sensing area of SAWR via electrospray deposition (ESD). The ESD method allows ng-resolution deposition of GO, optimizing the amount of sensing material. The proposed sensor consists of SWARs at three different resonant frequencies (180, 200 and 250 MHz) with a shared common sensing region, thus allowing direct analysis of sensor performances at different operating frequencies. Our findings reveal that the resonant frequency of the sensor impacts both measurement sensitivity and stability. A higher operating frequency ensures better sensitivity but suffers from a larger damping effect from absorbed water molecules. The maximum measurement sensitivity of 17.4 ppm/RH% is achieved with low drift. In addition, the developed sensor exhibits improved stability and sensitivity by as much as 150% and 75% in frequency shift and Quality factor (Q), respectively, by carefully selecting the operating frequencies at a given RH% range. Finally, the sensors are used for various hygienic applications, such as non-contact proximity detection and face mask inspection.

Hybrid Nanogenerators for Ocean Energy Harvesting: Mechanisms, Designs, and Applications.

The ocean holds vast potential as a renewable energy source, but harnessing its power has been challenging due to low-frequency and high-amplitude stimulation. However, hybrid nanogenerators (HNGs) offer a promising solution to convert ocean energy into usable power efficiently. With their high sensitivity and flexible design, HNGs are ideal for low-frequency environments and remote ocean regions. Combining triboelectric nanogenerators (TENGs) with piezoelectric nanogenerators (PENGs) and electromagnetic nanogenerators (EMGs) creates a unique hybrid system that maximizes energy harvesting. Ultimately, hybrid energy-harvesting systems offer a sustainable and reliable solution for growing energy needs. This study provides an in-depth review of the latest research on ocean energy harvesting by hybrid systems, focusing on self-powered applications. The article also discusses primary hybrid designs for devices, powering self-powered units such as wireless communication systems, climate monitoring systems, and buoys as applications. The potential of HNGs is enormous, and with rapid advancements in research and fabrication, these systems are poised to revolutionize ocean energy harvesting. It outlines the pros and cons of HNGs and highlights the major challenges that must be overcome. Finally, future outlooks for hybrid energy harvesters are also discussed.

Customizing the mechanical properties of additively manufactured metallic meta grain structure with sheet-based gyroid architecture.

The use of cellular structures has led to unprecedented outcomes in various fields involving optical and mechanical cloaking, negative thermal expansion, and a negative Poisson's ratio. The unique characteristics of periodic cellular structures primarily originate from the interconnectivity, periodicity, and unique design of the unit cells. However, the periodicity often induces unfavorable mechanical behaviors such as a "post-yielding collapse", and the mechanical performance is often limited by the design of the unit cells. Therefore, we propose a novel structure called a meta grain structure (MGS), which is inspired by a polycrystalline structure, to enhance flexibility in design and mechanical reliability. A total of 138 different MGSs were built and tested numerically, and the correlations between the design parameters (e.g., the relative density) and mechanical properties of the MGSs were rigorously analyzed. A systematic design methodology was developed to obtain the optimal design of the MGS with the target Young's modulus. This methodology makes it possible to build a unique structure that offers various design options and overcomes the current limitations of cellular structures. Furthermore, a systematic inverse design methodology makes it possible to produce an MGS that satisfies the required mechanical performance.

A focused review on three-dimensional bioprinting technology for artificial organ fabrication.

Three-dimensional (3D) bioprinting technology has attracted a great deal of interest because it can be easily adapted to many industries and research sectors, such as biomedical, manufacturing, education, and engineering. Specifically, 3D bioprinting has provided significant advances in the medical industry, since such technology has led to significant breakthroughs in the synthesis of biomaterials, cells, and accompanying elements to produce composite living tissues. 3D bioprinting technology could lead to the immense capability of replacing damaged or injured tissues or organs with newly dispensed cell biomaterials and functional tissues. Several types of bioprinting technology and different bio-inks can be used to replicate cells and generate supporting units as complex 3D living tissues. Bioprinting techniques have undergone great advancements in the field of regenerative medicine to provide 3D printed models for numerous artificial organs and transplantable tissues. This review paper aims to provide an overview of 3D-bioprinting technologies by elucidating the current advancements, recent progress, opportunities, and applications in this field. It highlights the most recent advancements in 3D-bioprinting technology, particularly in the area of artificial organ development and cancer research. Additionally, the paper speculates on the future progress in 3D-bioprinting as a versatile foundation for several biomedical applications.

Quartz crystal microbalance with thermally-controlled surface adhesion for an efficient fine dust collection and sensing.

The mass concentration of fine dust or particles acts as a standard measure to express the severity of air pollution. In connection with this, many related sensor technologies have been suggested for both indoor and outdoor uses. Among several technologies, the direct measurement of the dust mass using resonant platforms is the most preferable as it possesses multiple advantages including high sensitivity, low limit of detection, and a rapid response time. Such sensor performances directly rely on the adhesion quality between the sensor substrate and dust. In this work, we introduce a thermally controlled dust capturing scheme by integrating a polystyrene (PS) layer and microheater on quartz crystal microbalance (QCM). The Pt microheater can rapidly heat the sensor up to 100 °C, allowing a controlled switching between the soft and hard conditions of the PS film at a rapid rate. When the film is soft, the sensor can capture dust particle efficiently and we can calibrate the attached particle mass by measuring the resonance response. Compared to a bare QCM, our sensor used in this study exhibits 11 times larger detectable mass range. In addition, heated QCMs show a performance that is comparable to a high-cost particle sensing equipment such as an aerodynamic particle sizer and optical particle counter.

Preparation of Multifunctional N-Doped Carbon Quantum Dots from Citrus clementina Peel: Investigating Targeted Pharmacological Activities and the Potential Application for Fe3+ Sensing.

Carbon quantum dots (CQDs) have recently emerged as innovative theranostic nanomaterials, enabling fast and effective diagnosis and treatment. In this study, a facile hydrothermal approach for N-doped biomass-derived CQDs preparation from Citrus clementina peel and amino acids glycine (Gly) and arginine (Arg) has been presented. The gradual increase in the N-dopant (amino acids) nitrogen content increased the quantum yield of synthesized CQDs. The prepared CQDs exhibited good biocompatibility, stability in aqueous, and high ionic strength media, similar optical properties, while differences were observed regarding the structural and chemical diversity, and biological and antioxidant activity. The antiproliferative effect of CQD@Gly against pancreatic cancer cell lines (CFPAC-1) was observed. At the same time, CQD@Arg has demonstrated the highest quantum yield and antioxidant activity by DPPH scavenging radical method of 81.39 ± 0.39% and has been further used for the ion sensing and cellular imaging of cancer cells. The obtained results have demonstrated selective response toward Fe3+ detection, with linear response ranging from 7.0 µmol dm-3 to 50.0 µmol dm-3 with R2 = 0.9931 and limit of detection (LOD) of 4.57 ± 0.27 µmol dm-3. This research could be a good example of sustainable biomass waste utilization with potential for biomedical analysis and ion sensing applications.

Nanogenerator for determination of acoustic power in ultrasonic reactors.

This paper presents the novel use of a sonochemical reaction product as a sensing material in self-powered ultrasonic reactor devices for determination of ultrasound parameters. A piezoelectric nanogenerator was fabricated via sonochemical synthesis of SbSeI nanowires compressed into a bulk sample. The prepared device was used to develop two fast and simple evaluation methods for acoustic power in liquid. A calibration procedure was carried out for both methods using a VCX-750 ultrasonic processor. The ultrasound acoustic power was varied within a 150 W to 750 W range and the corresponding nanogenerator electrical responses were measured. The voltage signals of the first method fit the best with theoretical dependence. The second technique was based on the application of the Fast Fourier Transform (FFT) to the measured electric output. The results of these two approaches were convergent. Acoustic power values of 255(8) W and 222(7) W were determined for the Sonic-6 reactor using theoretical dependence fitting to experimental data and FFT analysis, respectively. Developed sensing technology possesses great potential for sonochemistry applications.

A Study on the Effects of Bottom Electrode Designs on Aluminum Nitride Contour-Mode Resonators.

This study presents the effects of bottom electrode designs on the operation of laterally vibrating aluminum nitride (AlN) contour-mode resonators (CMRs). A total of 160 CMRs were analyzed with varying bottom electrode areas at two resonant frequencies (f0) of about 230 MHz and 1.1 GHz. Specifically, we analyzed the impact of bottom electrode coverage rates on the resonator quality factor (Q) and electromechanical coupling (k2), which are important parameters for Radio Frequency (RF) and sensing applications. From our experiments, Q exhibited different trends to electrode coverage rates depending on the device resonant frequencies, while k2 increased with the coverage rate regardless of f0. Along with experimental measurements, our finite element analysis (FEA) revealed that the bottom electrode coverage rate determines the active (or vibrating) region of the resonator and, thus, directly impacts Q. Additionally, to alleviate thermoelastic damping (TED) and focus on mechanical damping effects, we analyzed the device performance at 10 K. Our findings indicated that a careful design of bottom electrodes could further improve both Q and k2 of AlN CMRs, which ultimately determines the power budget and noise level of the resonator in integrated oscillators and sensor systems.

High Efficiency Crumpled Carbon Nanotube Heaters for Low Drift Hydrogen Sensing.

This work presents the fabrication of crumpled carbon nanotubes (C-CNTs) thin film heaters and their application towards high sensitivity and low drift hydrogen gas sensing. Utilizing a spray coating of pristine multi-walled carbon nanotubes (MWCNTs) and thermal shrinkage of polystyrene (PS) substrate, we have fabricated C-CNTs with closely packed junctions. Joule heating of C-CNTs gives higher temperature at a given input voltage compared to as-deposited CNTs. In addition, temperature coefficient of resistance (TCR) is analyzed for accurate temperature control and measurement of the heater. The C-CNT heaters are capable of hydrogen gas sensing while demonstrating higher measurement sensitivities along with lower drift compared to as-deposited CNT devices. In addition, the self-heating of C-CNT heaters help rapid desorption of hydrogen, and thus allowing repetitive and stable sensor operation. Our findings reveal that both CNT morphologies and heating temperatures affect the hydrogen sensing performances.

Three-Dimensional Integration of Graphene via Swelling, Shrinking, and Adaptation.

The transfer of graphene from its growth substrate to a target substrate has been widely investigated for its decisive role in subsequent device integration and performance. Thus far, various reported methods of graphene transfer have been mostly limited to planar or curvilinear surfaces due to the challenges associated with fractures from local stress during transfer onto three-dimensional (3D) microstructured surfaces. Here, we report a robust approach to integrate graphene onto 3D microstructured surfaces while maintaining the structural integrity of graphene, where the out-of-plane dimensions of the 3D features vary from 3.5 to 50 µm. We utilized three sequential steps: (1) substrate swelling, (2) shrinking, and (3) adaptation, in order to achieve damage-free, large area integration of graphene on 3D microstructures. Detailed scanning electron microscopy, atomic force microscopy, Raman spectroscopy, and electrical resistance measurement studies show that the amount of substrate swelling as well as the flexural rigidities of the transfer film affect the integration yield and quality of the integrated graphene. We also demonstrate the versatility of our approach by extension to a variety of 3D microstructured geometries. Lastly, we show the integration of hybrid structures of graphene decorated with gold nanoparticles onto 3D microstructure substrates, demonstrating the compatibility of our integration method with other hybrid nanomaterials. We believe that the versatile, damage-free integration method based on swelling, shrinking, and adaptation will pave the way for 3D integration of two-dimensional (2D) materials and expand potential applications of graphene and 2D materials in the future.

Parallel nanoimaging and nanolithography using a heated microcantilever array.

We report parallel topographic imaging and nanolithography using heated microcantilever arrays integrated into a commercial atomic force microscope (AFM). The array has five AFM cantilevers, each of which has an internal resistive heater. The temperatures of the cantilever heaters can be monitored and controlled independently and in parallel. We perform parallel AFM imaging of a region of size 550 µm × 90 µm, where the cantilever heat flow signals provide a measure of the nanometer-scale substrate topography. At a cantilever scan speed of 1134 µm s(-1), we acquire a 3.1 million-pixel image in 62 s with noise-limited vertical resolution of 0.6 nm and pixels of size 351 nm × 45 nm. At a scan speed of 4030 µm s(-1) we acquire a 26.4 million pixel image in 124 s with vertical resolution of 5.4 nm and pixels of size 44 nm × 43 nm. Finally, we demonstrate parallel nanolithography with the cantilever array, including iterations of measure-write-measure nanofabrication, with each cantilever operating independently.

Parallelization of thermochemical nanolithography.

One of the most pressing technological challenges in the development of next generation nanoscale devices is the rapid, parallel, precise and robust fabrication of nanostructures. Here, we demonstrate the possibility to parallelize thermochemical nanolithography (TCNL) by employing five nano-tips for the fabrication of conjugated polymer nanostructures and graphene-based nanoribbons.

Ultrananocrystalline diamond tip integrated onto a heated atomic force microscope cantilever.

We report a wear-resistant ultrananocrystalline (UNCD) diamond tip integrated onto a heated atomic force microscope (AFM) cantilever and UNCD tips integrated into arrays of heated AFM cantilevers. The UNCD tips are batch-fabricated and have apex radii of approximately 10 nm and heights up to 7 µm. The solid-state heater can reach temperatures above 600 °C and is also a resistive temperature sensor. The tips were shown to be wear resistant throughout 1.2 m of scanning on a single-crystal silicon grating at a force of 200 nN and a speed of 10 µm s(-1). Under the same conditions, a silicon tip was completely blunted. We demonstrate the use of these heated cantilevers for thermal imaging in both contact mode and intermittent contact mode, with a vertical imaging resolution of 1.9 nm. The potential application to nanolithography was also demonstrated, as the tip wrote hundreds of polyethylene nanostructures.