Switchable Power Generation in Triboelectric Nanogenerator Toward Chip-Less Wearable Power Module Applications.

A conceptual shift toward next-generation wearable electronics is driving research into self-powered electronics technologies that can be independently operated without plugging into the grid for external power feeding. Triboelectric nanogenerators (TENGs) are emerging as a key component of self-powered electronics, but a power type mismatch between supply and demand limits their direct implementation into wearable self-powered electronics. Here, a TENG with switchable power mode capability is reported where the charge flow direction is modulated over the course of slow and random mechanical stimuli, with exceptional rectification capabilities as high as ≈133, stable outputs over the cycles, and design flexibility in different platforms. Importantly, the remarkable switchable power generation with fabric counter materials illuminates a new path for the smooth integration of flexible TENGs into wearable self-powered electronics.

Detection of Biomolecules Using Solid-State Nanopores Fabricated by Controlled Dielectric Breakdown.

Nanopore sensor technology is widely used in biomolecular detection due to its advantages of low cost and easy operation. In a variety of nanopore manufacturing methods, controlled dielectric breakdown has the advantages of a simple manufacturing process and low cost under the premise of ensuring detection performance. In this paper, we have made enhancements to the applied pulses in controlled dielectric breakdown and utilized the improved dielectric breakdown technique to fabricate silicon nitride nanopores with diameters of 5 to 15 nm. Our improved fabrication method offers the advantage of precise control over the nanopore diameter (±0.4 nm) and enhances the symmetry of the nanopore. After fabrication, we performed electrical characterization on the nanopores, and the IV characteristics exhibited high linearity. Subsequently, we conducted detection experiments for DNA and protein using the prepared nanopores to assess the detection performance of the nanopores fabricated using our method. In addition, we also give a physical model of molecule translocation through the nanopores to give a reasonable explanation of the data processing results.

Use of a solid-state nanopore for profiling the transferrin receptor protein and distinguishing between transferrin receptor and its ligand protein.

A nanopore device is capable of providing single-molecule level information of an analyte as they translocate through the sensing aperture-a nanometer-sized through-hole-under the influence of an applied electric field. In this study, a silicon nitride (Six Ny )-based nanopore was used to characterize the human serum transferrin receptor protein (TfR) under various applied voltages. The presence of dimeric forms of TfR was found to decrease exponentially as the applied electric field increased. Further analysis of monomeric TfR also revealed that its unfolding behaviors were positively dependent on the applied voltage. Furthermore, a comparison between the data of monomeric TfR and its ligand protein, human serum transferrin (hSTf), showed that these two protein populations, despite their nearly identical molecular weights, could be distinguished from each other by means of a solid-state nanopore (SSN). Lastly, the excluded volumes of TfR were experimentally determined at each voltage and were found to be within error of their theoretical values. The results herein demonstrate the successful application of an SSN for accurately classifying monomeric and dimeric molecules while the two populations coexist in a heterogeneous mixture.

Spectroscopy of Laser-Induced Dielectric Breakdown Plasma in Mixtures of Air with Inert Gases Ar, He, Kr, and Xe.

The generation of ozone and nitrogen oxides by laser-induced dielectric breakdown (LIDB) in mixtures of air with noble gases Ar, He, Kr, and Xe is investigated using OES and IR spectroscopy, mass spectrometry, and absorption spectrophotometry. It is shown that the formation of NO and NO2 noticeably depends on the type of inert gas; the more complex electronic configuration and the lower ionization potential of the inert gas led to increased production of NO and NO2. The formation of ozone occurs mainly due to the photolytic reaction outside the gas discharge zone. Equilibrium thermodynamic analysis showed that the formation of NO in mixtures of air with inert gases does not depend on the choice of an inert gas, while the equilibrium concentration of the NO+ ion decreases with increasing complexity of the electronic configuration of an inert gas.

Reliability Characteristics of Metal-Insulator-Semiconductor Capacitors with Low-Dielectric-Constant Materials.

In this study, the reliability characteristics of metal-insulator-semiconductor (MIS) capacitor structures with low-dielectric-constant (low-k) materials have been investigated in terms of metal gate area and geometry and thickness of dielectric film effects. Two low-k materials, dense and porous low-k films, were used. Experimental results indicated that the porous low-k films had shorter breakdown times, lower Weibull slope parameters and electric field acceleration factors, and weaker thickness-dependence breakdowns compared to the dense low-k films. Additionally, a larger derivation in dielectric breakdown projection model and a single Weilbull plot of the breakdown time distributions from various areas merging was observed. This study also pointed out that the porous low-k film in the irregular-shaped metal gate MIS capacitor had a larger dielectric breakdown time than that in the square- and circle-shaped samples, which violates the trend of the sustained electric field. As a result, another breakdown mechanism exists in the irregular-shaped sample, which is required to explore in the future work.

Using an insulating fiber as the sampling probe and ionization substrate for ambient ionization-mass spectrometric analysis of volatile, semi-volatile, and polar analytes.

A sharp metal needle used as the ionization emitter in conventional atmospheric pressure chemical ionization (APCI) mass spectrometry (MS) is usually required for analyte ionization through corona discharge (i.e., gas discharge). Nevertheless, we herein demonstrate that an insulating fiber (tip diameter: 10-60 µm; length: ~ 1 cm) made of glass or bamboo can function as an APCI-like ionization emitter. Although no direct electric contact is made on the fiber, the ionization of volatiles and semi-volatiles occurs when the fiber is placed close (~ 1 mm) to the inlet of the mass spectrometer. No analyte ion signals can be observed without placing the insulating fiber in front of the mass spectrometer. The generation of ion species mainly relies on the electric field provided by the mass spectrometer. Presumably, owing to the high electric field provided by the mass spectrometer, the dielectric breakdown voltages of gas molecules in the air and the fiber are overcome, leading to the ionization of analytes in gas phase. In addition, the insulating fiber can function as a holder for sample solutions. Electrospray ionization-like processes derived from polar analytes such as amino acids, peptides, and proteins can readily occur when the insulating fiber deposited with a sample droplet is placed close to the inlet of the mass spectrometer. The feasibility of using the current approach for the detection of nonpolar and polar analytes from complex fetal bovine serum samples without tedious sample pretreatment is demonstrated in this work. The main advantage of using the suggested fiber is that the fiber can be used as the sampling probe to pick up samples and placed in front of a mass spectrometer for direct MS analysis. The application of using a robust, insulating, and disposable probe to pick up samples from real samples such as onion, honey, and pork samples followed by direct MS analysis is also demonstrated.

Understanding Electrical Conduction and Nanopore Formation During Controlled Breakdown.

Controlled breakdown has recently emerged as a highly appealing technique to fabricate solid-state nanopores for a wide range of biosensing applications. This technique relies on applying an electric field of approximately 0.4-1 V nm-1 across the membrane to induce a current, and eventually, breakdown of the dielectric. Although previous studies have performed controlled breakdown under a range of different conditions, the mechanism of conduction and breakdown has not been fully explored. Here, electrical conduction and nanopore formation in SiNx membranes during controlled breakdown is studied. It is demonstrated that for Si-rich SiNx , oxidation reactions that occur at the membrane-electrolyte interface limit conduction across the dielectric. However, for stoichiometric Si3 N4 the effect of oxidation reactions becomes relatively small and conduction is predominately limited by charge transport across the dielectric. Several important implications resulting from understanding this process are provided which will aid in further developing controlled breakdown in the coming years, particularly for extending this technique to integrate nanopores with on-chip nanostructures.

Assessment of 1/f noise associated with nanopores fabricated through chemically tuned controlled dielectric breakdown.

Recently, we developed a fabrication method-chemically-tuned controlled dielectric breakdown (CT-CDB)-that produces nanopores (through thin silicon nitride membranes) surpassing legacy drawbacks associated with solid-state nanopores (SSNs). However, the noise characteristics of CT-CDB nanopores are largely unexplored. In this work, we investigated the 1/f noise of CT-CDB nanopores of varying solution pH, electrolyte type, electrolyte concentration, applied voltage, and pore diameter. Our findings indicate that the bulk Hooge parameter (αb ) is about an order of magnitude greater than SSNs fabricated by transmission electron microscopy (TEM) while the surface Hooge parameter (αs ) is ∼3 order magnitude greater. Theαs of CT-CDB nanopores was ∼5 orders of magnitude greater than theirαb , which suggests that the surface contribution plays a dominant role in 1/f noise. Experiments with DNA exhibited increasing capture rates with pH up to pH ∼8 followed by a drop at pH ∼9 perhaps due to the onset of electroosmotic force acting against the electrophoretic force. The1/f noise was also measured for several electrolytes and LiCl was found to outperform NaCl, KCl, RbCl, and CsCl. The 1/f noise was found to increase with the increasing electrolyte concentration and pore diameter. Taken together, the findings of this work suggest the pH approximate 7-8 range to be optimal for DNA sensing with CT-CDB nanopores.

The influence of electrolyte concentration on nanofractures fabricated in a 3D-printed microfluidic device by controlled dielectric breakdown.

A three-dimensional-printed microfluidic device made of a thermoplastic material was used to study the creation of molecular filters by controlled dielectric breakdown. The device was made from acrylonitrile butadiene styrene by a fused deposition modeling three-dimensional printer and consisted of two V-shaped sample compartments separated by 750 µm of extruded plastic gap. Nanofractures were formed in the thin piece of acrylonitrile butadiene styrene by controlled dielectric breakdown by application voltage of 15-20 kV with the voltage terminated when reaching a defined current threshold. Variation of the size of the nanofractures was achieved by both variation of the current threshold and by variation of the ionic strength of the electrolyte used for breakdown. Electrophoretic transport of two proteins, R-phycoerythrin (RPE; <10 nm in size) and fluorescamine-labeled BSA (f-BSA; 2-4 nm), was used to monitor the size and transport properties of the nanofractures. Using 1 mM phosphate buffer, both RPE and f-BSA passed through the nanofractures when the current threshold was set to 25 µA. However, when the threshold was lowered to 10 µA or lower, RPE was restricted from moving through the nanofractures. When we increased the electrolyte concentration during breakdown from 1 to 10 mM phosphate buffer, BSA passed but RPE was blocked when the threshold was equal to, or lower than, 25 µA. This demonstrates that nanofracture size (pore area) is directly related to the breakdown current threshold but inversely related to the concentration of the electrolyte used for the breakdown process.

Increased dwell time and occurrence of dsDNA translocation events through solid state nanopores by LiCl concentration gradients.

Solid-state nanopore based biosensors are cost effective, high-throughput engines for single molecule detection of biomolecules with the added benefit of size modification. Progress in the translation of the science into a viable diagnostic tool is impeded by inadequate sensitivity of data acquisition systems in detection of fast DNA translocations through the pore. To combat this, slowing the transport of DNA through the nanopore by use of various media or by altering experimental parameters is common. Applying a concentration gradient of KCl in the experimental ionic solution has been shown to effectively prolong dwell times as well as increase the capture rate of DNA by the nanopore. Our previous work has corroborated the ability of LiCl ionic solution to slow down the transport of dsDNA through the nanopore by up to 10-fold through cation-DNA interactions. However, this drastically reduced the event occurrence frequency, thus hindering the efficacy of this system as a reliable biosensor downstream. Here, we present the use of a concentration gradient of lithium chloride ionic solution to increase the event frequency of single molecule dsDNA translocation through a solid state nanopore. By using 0.5 M/3 M LiCl on the cis/trans chambers respectively, average dwell times experienced up to a 3-fold increase when compared to experiments run in symmetric 1 M LiCl. Additionally, experiments using the 0.5 M/3 M displayed a greater than 10-fold increase in event frequency, confirming the capture propensity of the asymmetric conditions.

Conductance-based profiling of nanopores: Accommodating fabrication irregularities.

Solid-state nanopores are nanoscale channels through otherwise impermeable membranes. Single molecules or particles can be passed through electrolyte-filled nanopores by, e.g. electrophoresis, and then detected through the resulting physical displacement of ions within the nanopore. Nanopore size, shape, and surface chemistry must be carefully controlled, and on extremely challenging <10 nm-length scales. We previously developed a framework to characterize nanopores from the time-dependent changes in their conductance as they are being formed through solution-phase nanofabrication processes with the appeal of ease and accessibility. We revisited this simulation work, confirmed the suitability of the basic conductance equation using the results of time-dependent experimental conductance measurements during nanopore fabrication by Yanagi et al., and then deliberately relaxed the model constraints to allow for (i) the presence of defects; and (ii) the formation of two small pores instead of one larger one. Our simulations demonstrated that the time-dependent conductance formalism supports the detection and characterization of defects, as well as the determination of pore number, but with implementation performance depending on the measurement context and results. In some cases, the ability to discriminate numerically between the correct and incorrect nanopore profiles was slight, but with accompanying differences in candidate nanopore dimensions that could yield to post-fabrication conductance profiling, or be used as convenient uncertainty bounds. Time-dependent nanopore conductance thus offers insight into nanopore structure and function, even in the presence of fabrication defects.

Solid-state nanopore fabrication in LiCl by controlled dielectric breakdown.

Nanopore fabrication via the controlled dielectric breakdown (CDB) method offers an opportunity to create solid-state nanopores directly in salt solution with sub-nanometer precision. Driven by trap assisted current tunneling, the method uses localized defects, or traps, in the dielectric material to isolate a breakdown point and fabricate a single pore in less than 10 minutes. Here we present an approach to controlled dielectric breakdown of SiNx in which the nanopore is fabricated in LiCl buffer instead of the traditional KCl buffer. Direct fabrication in LiCl buffer promotes a uniform, symmetric, cylindrical nanopore structure that is fully wet and can be used for experiments in situ. We have shown that fabrication in LiCl reduces the necessity for overnight pore stabilization and allows for the desired analyte to be added in significantly less time than it would take if fabrication was performed in KCl. Pores created by this approach can be used for biosensing applications, including the detection of double-stranded DNA. DNA translocation experiments were conducted in both LiCl and KCl buffer. Experiments conducted in LiCl buffer resulted in about a 2-fold increase in dsDNA transport duration when compared to experiments conducted in KCl buffer of the same concentration. An increase in transport duration of over 10-fold in comparison to KCl was observed when the concentration of the LiCl buffer was increased by a factor of 3.

Self-Aligned Plasmonic Nanopores by Optically Controlled Dielectric Breakdown.

We present a novel cost-efficient method for the fabrication of high-quality self-aligned plasmonic nanopores by means of an optically controlled dielectric breakdown. Excitation of a plasmonic bowtie nanoantenna on a dielectric membrane localizes the high-voltage-driven breakdown of the membrane to the hotspot of the enhanced optical field, creating a nanopore that is automatically self-aligned to the plasmonic hotspot of the bowtie. We show that the approach provides precise control over the nanopore size and that these plasmonic nanopores can be used as single molecule DNA sensors with a performance matching that of TEM-drilled nanopores. The principle of optically controlled breakdown can also be used to fabricate nonplasmonic nanopores at a controlled position. Our novel fabrication process guarantees alignment of the nanopore with the optical hotspot of the nanoantenna, thus ensuring that pore-translocating biomolecules interact with the concentrated optical field that can be used for detection and manipulation of analytes.

Electrokinetic Size and Mobility Traps for On-site Therapeutic Drug Monitoring.

The extraction of target analytes from biological samples is a bottleneck in analysis. A microfluidic device featuring an electrokinetic size and mobility trap was formed by two nanojunctions of different pore size to extract and concentrate analytical targets from complex samples. The trap was seamlessly coupled with electrophoretic separation for quantitative analysis. The device was applied to the analysis of ampicillin levels in blood within 5 min and a linear response over the range of 2.5-20 µg mL(-1). This covers the recommended levels for treating sepsis, a critical condition with 30 to 50% mortality and unpredicted drug levels. The device provides a new opportunity for on-site therapeutic drug monitoring, which should enable quick and accurate dosing and may save lives in such critical conditions.

Automated fabrication of 2-nm solid-state nanopores for nucleic acid analysis.

We demonstrate the automated and reproducible fabrication of sub-2-nm nanopores in 10-nm thick silicon nitride membranes, through controlled dielectric breakdown in solution. Our results reveal that under the appropriate conditions, nanopores can be fabricated with a size no larger than 2.0 ± 0.5-nm in diameter for a sample of N = 23 nanopores, with an average and standard deviation of 1.3 ± 0.6-nm. The dimensions of these nanopores are confirmed by using individual translocating DNA molecules as molecular rulers. We show that a 2.0-nm and a 2.1-nm diameter nanopore are capable of distinguishing single-stranded DNA versus double-stranded DNA, and that a 2.4-nm diameter nanopore can be used to investigate the overstretching transition in short dsDNA fragments. These results highlight the reliability and precision of the automated fabrication of nanopores via controlled dielectric breakdown, showing great promise for the manufacturing of future nanopore-based technologies.

Increased Deep Trap Density in Interfacial Engineered Nanocomposite Revealed by Sequential Kelvin Probe Force Microscopy for High Dielectric Energy Storage.

Nanocomposites combining inorganic nanoparticles with high dielectric constant and polymers with high breakdown strength are promising for the high energy density storage of electricity, and carrier traps can significantly affect the dielectric breakdown process. Nevertheless, there still lacks direct experimental evidence on how nanoparticles affect the trap characteristics of nanocomposites, especially in a spatially resolved manner. Here, a technique is developed to image the trap distribution based on sequential Kelvin probe force microscopy (KPFM) in combination with the isothermal surface potential decay (ISPD) technique, wherein both shallow and deep trap densities and the corresponding energy levels can be mapped with nanoscale resolution. The technique is first validated using the widely-used commercial biaxially oriented polypropylene, yielding consistent results with macroscopic ISPD. The technique is then applied to investigate polyvinylidene fluoride-based nanocomposites filled with barium titanate nanoparticles, revealing higher deep trap density around surface-modified nanoparticles, which correlates well with its increased breakdown strength. This technique thus provides a powerful spatially resolved tool for understanding the microscopic mechanism of dielectric breakdown of nanocomposites.

Micro/nanofluidic device for tamsulosin therapeutic drug monitoring in patients with benign prostatic hyperplasia at point of care.

Discovering the balance between toxicity and efficacy for many drugs requires therapeutic drug monitoring (TDM) of their concentrations in the blood. Here, a hot-embossed microfluidic device with a new design integrated to a nanofracture is presented for purification of blood samples from numerous proteins and cells, allowing to the separation of small molecules from blood matrix. The device was used to separate and quantitatively detect tamsulosin drug after derivatization with fluorescamine reagent, allowing converting it from a neutral molecule into a charged fluorescent complex under the experimental conditions, and thus its separation by electrophoresis. The device is portable and easy operated, and the presented method showed good linearity (R2 = 0.9948) over a concentration range of 0.1-1 µg/mL. The relative standard deviation (RSD%) was below 10% (n = 3), indicating good precisions, and the limit of detection (LOD) and limit of quantitation (LOQ) values were estimated to be 0.1 and 0.55 µg/mL, respectively. Whole blood samples from 10 patients with benign prostatic hyperplasia (BPH) were analyzed, showing good percentage recoveries of tamsulosin in whole blood. This point-of-care (POC), low-cost method could increase the convenience of patients and doctors, make therapies safer, and make TDM available in different regions and places.

The Understanding and Compact Modeling of Reliability in Modern Metal-Oxide-Semiconductor Field-Effect Transistors: From Single-Mode to Mixed-Mode Mechanisms.

With the technological scaling of metal-oxide-semiconductor field-effect transistors (MOSFETs) and the scarcity of circuit design margins, the characteristics of device reliability have garnered widespread attention. Traditional single-mode reliability mechanisms and modeling are less sufficient to meet the demands of resilient circuit designs. Mixed-mode reliability mechanisms and modeling have become a focal point of future designs for reliability. This paper reviews the mechanisms and compact aging models of mixed-mode reliability. The mechanism and modeling method of mixed-mode reliability are discussed, including hot carrier degradation (HCD) with self-heating effect, mixed-mode aging of HCD and Bias Temperature Instability (BTI), off-state degradation (OSD), on-state time-dependent dielectric breakdown (TDDB), and metal electromigration (EM). The impact of alternating HCD-BTI stress conditions is also discussed. The results indicate that single-mode reliability analysis is insufficient for predicting the lifetime of advanced technology and circuits and provides guidance for future mixed-mode reliability analysis and modeling.

Morphology around Nanopores Fabricated by Laser-Assisted Dielectric Breakdown and Its Impact on Ion and DNA Transport and Sensing.

Laser-assisted controlled dielectric breakdown (LaCBD) has emerged as an alternative to conventional CBD-based nanopore fabrication due to its localization capability, facilitated by the photothermal-induced thinning down in the hot spot. Here, we reported the potential impact of the laser on forming debris around the nanopore region in LaCBD. The debris was clearly observable by scanning electron microscopy (SEM) and photoluminescence (PL) spectroscopy. We found that debris formation is a unique phenomenon in LaCBD that is not observable in the conventional CBD approach. We also found that the LaCBD-induced debris is more evident when the laser power and voltage stress are higher. Moreover, the debris is asymmetrically distributed on the top and bottom sides of the membrane. We also found unexpected rectified ionic and molecular transport in those LaCBD nanopores with debris. Based on these observations, we developed and validated a model describing the debris formation kinetics in LaCBD by considering the generation, diffusion, drift, and gravity in viscous mediums. These findings indicate that while laser aids in nanopore localization, precautions should be taken due to the potential formation of debris and rectification of molecular transport. This study provides valuable insights into the kinetics of LaCBD and the characteristics of the LaCBD nanopore.

Comparison of CoW/SiO2 and CoB/SiO2 Interconnects from the Perspective of Electrical and Reliability Characteristics.

As the feature size of integrated circuits has been scaled down to 10 nm, the rapid increase in the electrical resistance of copper (Cu) metallization has become a critical issue. To alleviate the resistance increases of Cu lines, co-sputtered CoW and CoB alloying metals were investigated as conductors and barriers in this study. Annealing CoM (M = W or B)/SiO2/p-Si structures reduced the resistivity of CoM alloys, removed sputtering-deposition-induced damage, and promoted adhesion. Additionally, both annealed CoW/SiO2 or CoB/SiO2 structures displayed a negligible Vfb shift from capacitance-voltage measurements under electrical stress, revealing an effective barrier capacity, which is attributed to the formation of MOx layers at the CoM/SiO2 interface. Based on the thermodynamics, the B2O3 layer tends to form more easily than the WOx layer. Hence, the annealed CoB/SiO2/p-Si MIS capacitor had a higher capacitance and a larger breakdown strength did than the annealed CoW/SiO2/p-Si MIS capacitor.