Highly sensitive flexible heat flux sensor based on a microhole array for ultralow to high temperatures.

With the growing demand for thermal management of electronic devices, cooling of high-precision instruments, and biological cryopreservation, heat flux measurement of complex surfaces and at ultralow temperatures has become highly imperative. However, current heat flux sensors (HFSs) are commonly used in high-temperature scenarios and have problems when applied in low-temperature conditions, such as low sensitivity and embrittlement. In this study, we developed a flexible and highly sensitive HFS that can operate at ultralow to high temperatures, ranging from -196 °C to 273 °C. The sensitivities of HFSs with thicknesses of 0.2 mm and 0.3 mm, which are efficiently manufactured by the screen-printing method, reach 11.21 µV/(W/m2) and 13.43 µV/(W/m2), respectively. The experimental results show that there is a less than 3% resistance change from bending to stretching. Additionally, the HFS can measure heat flux in both exothermic and absorptive cases and can measure heat flux up to 25 kW/m2. Additionally, we demonstrate the application of the HFS to the measurement of minuscule heat flux, such as heat dissipation of human skin and cold water. This technology is expected to be used in heat flux measurements at ultralow temperatures or on complex surfaces, which has great importance in the superconductor and cryobiology field.

PoolNet+: Exploring the Potential of Pooling for Salient Object Detection.

We explore the potential of pooling techniques on the task of salient object detection by expanding its role in convolutional neural networks. In general, two pooling-based modules are proposed. A global guidance module (GGM) is first built based on the bottom-up pathway of the U-shape architecture, which aims to guide the location information of the potential salient objects into layers at different feature levels. A feature aggregation module (FAM) is further designed to seamlessly fuse the coarse-level semantic information with the fine-level features in the top-down pathway. We can progressively refine the high-level semantic features with these two modules and obtain detail enriched saliency maps. Experimental results show that our proposed approach can locate the salient objects more accurately with sharpened details and substantially improve the performance compared with the existing state-of-the-art methods. Besides, our approach is fast and can run at a speed of 53 FPS when processing a 300 ×400 image. To make our approach better applied to mobile applications, we take MobileNetV2 as our backbone and re-tailor the structure of our pooling-based modules. Our mobile version model achieves a running speed of 66 FPS yet still performs better than most existing state-of-the-art methods. To verify the generalization ability of the proposed method, we apply it to the edge detection, RGB-D salient object detection, and camouflaged object detection tasks, and our method achieves better results than the corresponding state-of-the-art methods of these three tasks. Code can be found at http://mmcheng.net/poolnet/.

Influences of RF Magnetron Sputtering Power and Gas Flow Rate on a High Conductivity and Low Drift Rate of Tungsten-Rhenium Thin-Film Thermocouples.

Thin-Film Thermocouples (TFTCs) are characterized by their high spatial resolutions, low cost, high efficiency and low interference on the air flow. However, the thermal stability of TFTCs should be further improved for application since their accuracy is influenced by joule heat and temperature time drift. In this paper, 3D molecular dynamics and finite element analysis are used for structural design. The effects of RF magnetron sputtering power and gas flow rate on conductivity and temperature time drift rate (DT) of high thermal stability tungsten-rhenium (95% W/5% Re vs. 74% W/26% Re) TFTCs were analyzed. According to the experimental results, the average Seebeck coefficient reached 31.1 µV/°C at 900 °C temperature difference (hot junction 1040 °C) with a repeatability error at ±1.37% in 33 h. The conductivity is 17.1 S/m, which is approximately 15.2 times larger than the compared tungsten-rhenium sample we presented, and the DT is 0.92 °C/h (1040 °C for 5 h), which is 9.5% of the old type we presented and 4.5% of compared ITO sample. The lumped capacity method test shows that the response time is 11.5 ms at 300 °C. This indicated an important significance in real-time temperature measurement for narrow spaces, such as the aero-engine combustion chamber.

Rethinking the U-Shape Structure for Salient Object Detection.

The U-shape structure has shown its advantage in salient object detection for efficiently combining multi-scale features. However, most existing U-shape-based methods focused on improving the bottom-up and top-down pathways while ignoring the connections between them. This paper shows that we can achieve the cross-scale information interaction by centralizing these connections, hence obtaining semantically stronger and positionally more precise features. To inspire the newly proposed strategy's potential, we further design a relative global calibration module that can simultaneously process multi-scale inputs without spatial interpolation. Our approach can aggregate features more effectively while introducing only a few additional parameters. Our approach can cooperate with various existing U-shape-based salient object detection methods by substituting the connections between the bottom-up and top-down pathways. Experimental results demonstrate that our proposed approach performs favorably against the previous state-of-the-arts on five widely used benchmarks with less computational complexity. The source code will be publicly available.

Optimization on thermoelectric characteristics of indium tin oxide/indium oxide thin film thermocouples based on screen printing technology.

In this work, indium tin oxide (ITO)/indium oxide (In2O3) thin film thermocouples (TFTCs) were prepared based on screen printing technology for high temperature measurement. With terpilenol as solvent, epoxy resin and polyether amine as binders and glass powders as additives, the ITO and In2O3 slurries were printed onto the Al2O3 substrate to form thermocouples. The effect on thermoelectric properties of the TFTCs with heat treatment and different contents of additives was investigated through microstructure observation and thermal cycle test. The static calibration experiment shows that the annealed TFTCs with 7.5 wt. % glass powders additives have the maximum Seebeck coefficient. The thermoelectric voltage output of the TFTCs can reach 126.5 mV at 1275 °C while the temperature difference is 1160 °C and the sensitivity of the TFTCs was 109.1 µV/°C. The drift rate of the TFTCs was 8.34 °C/h at a measuring time of 20 min at 1275 °C. The TFTCs prepared via screen printing technology with excellent thermoelectric properties and thermal stability are aimed to be a viable replacement for practical applications.

High-Performance Temperature Sensor by Employing Screen Printing Technology.

In the present study, a high-performance n-type temperature sensor was developed by a new and facile synthesis approach, which could apply to ambient temperature applications. As impacted by the low sintering temperature of flexible polyimide substrates, a screen printing technology-based method to prepare thermoelectric materials and a low-temperature heat treatment process applying to polymer substrates were proposed and achieved. By regulating the preparation parameters of the high-performance n-type indium oxide material, the optimal proportioning method and the post-treatment process method were developed. The sensors based on thermoelectric effects exhibited a sensitivity of 162.5 µV/°C, as well as a wide range of temperature measurement from ambient temperature to 223.6 °C. Furthermore, it is expected to conduct temperature monitoring in different scenarios through a sensor prepared in masks and mechanical hands, laying a foundation for the large-scale manufacturing and widespread application of flexible electronic skin and devices.

A thin-film temperature sensor based on a flexible electrode and substrate.

Accurate temperature measurements can efficiently solve numerous critical problems and provide key information. Herein, a flexible micro-three-dimensional sensor, with a combination of platinum and indium oxide to form thermocouples, is designed and fabricated by a microfabrication process to achieve in situ real-time temperature measurements. The stability and reliability of the sensor are greatly improved by optimizing the process parameters, structural design, and preparation methods. A novel micro-three-dimensional structure with better malleability is designed, which also takes advantage of the fast response of a two-dimensional thin film. The as-obtained flexible temperature sensor with excellent stability and reliability is expected to greatly contribute to the development of essential components in various emerging research fields, including bio-robot and healthcare systems. The model of the application sensor in a mask is further proposed and designed to realize the collection of health information, reducing the number of deaths caused by the lack of timely detection and treatment of patients.

Study on the characteristics of thermo-electrodes of various deposition parameters for the flexible temperature sensor.

In the paper, the flexible temperature sensor based on polyimide is designed and fabricated by magnetron sputtering technology. The impact of vacuum degree, sputtering power, and argon flow rate on the roughness and deposition rate of two thermo-electrodes [indium tin oxide (ITO)/indium oxide (In2O3)] is investigated with orthogonal experiment. The thermoelectric properties of the sensor are greatly improved by low temperature heat treatment. The sensitivity of the ITO film and In2O3 film increases by 2.61 times and 2.89 times, respectively, after 1 h low-temperature heat treatment. According to the comprehensive evaluation, an innovative step annealing process is proposed to optimize the heat treatment of the prepared thermo-electrodes. The fabricated flexible thin film thermocouples exhibit great operating characteristics in the low temperature measurement range. When the hot end's temperature reaches 181.5 °C, the thermoelectric force can reach 7.84 mV and the average Seebeck coefficient can reach 50.55 µV/°C. The repeatability and hysteresis error of the sensor is ±0.88% and 1.90%, respectively. The sensor in this work shows great application potential for in situ real-time temperature measurement in robotic dexterous hands, electronic skin, and foldable devices.

Dynamic Feature Integration for Simultaneous Detection of Salient Object, Edge and Skeleton.

Salient object segmentation, edge detection, and skeleton extraction are three contrasting low-level pixel-wise vision problems, where existing works mostly focused on designing tailored methods for each individual task. However, it is inconvenient and inefficient to store a pre-trained model for each task and perform multiple different tasks in sequence. There are methods that solve specific related tasks jointly but require datasets with different types of annotations supported at the same time. In this paper, we first show some similarities shared by these tasks and then demonstrate how they can be leveraged for developing a unified framework that can be trained end-to-end. In particular, we introduce a selective integration module that allows each task to dynamically choose features at different levels from the shared backbone based on its own characteristics. Furthermore, we design a task-adaptive attention module, aiming at intelligently allocating information for different tasks according to the image content priors. To evaluate the performance of our proposed network on these tasks, we conduct exhaustive experiments on multiple representative datasets. We will show that though these tasks are naturally quite different, our network can work well on all of them and even perform better than current single-purpose state-of-the-art methods. In addition, we also conduct adequate ablation analyses that provide a full understanding of the design principles of the proposed framework. To facilitate future research, source code will be released.

Facile fabrication of zinc oxide coated superhydrophobic and superoleophilic meshes for efficient oil/water separation.

Zinc oxide (ZnO) coated superhydrophobic and superoleophilic stainless steel meshes are facilely fabricated via chemical immersion growth and subsequent surface modification. The as-prepared meshes show good mechanical durability, chemical stability and corrosion-resistant properties due to a combination of the hierarchical ZnO structure and the low surface energy modification. More importantly, the as-prepared meshes are used for highly efficient separation of various oil/water mixtures. Meanwhile, a new oil skimmer based on the as-prepared mesh is proposed to spontaneously collect floating oil with high separation efficiency and desirable durability.

Data processing and analysis for mass spectrometry imaging.

Mass spectrometry imaging produces large numbers of spectra that need to be efficiently stored, processed, and analyzed. In this chapter, we describe the protocol and methods for data processing, visualization, and statistical analysis, with related techniques and tools available presented. Examples are given with data collected for a 3D MS imaging of a mouse brain and 2D MS imaging of human bladder tissues.

Direct mass spectrometry analysis of biofluid samples using slug-flow microextraction nano-electrospray ionization.

Direct mass spectrometry (MS) analysis of biofluids with simple procedures represents a key step in the translation of MS techniques to clinical and point-of-care applications. The current study reports the development of a single-step method using slug-flow microextraction and nano-electrospray ionization for MS analysis of organic compounds in blood and urine. High sensitivity and quantitation precision have been achieved in the analysis of therapeutic and illicit drugs in 5 µL samples. Real-time chemical derivatization has been incorporated for analyzing anabolic steroids. The monitoring of enzymatic functions has also been demonstrated with cholinesterase in wet blood. The reported study encourages the future development of disposable cartridges, which function with simple operation to replace the traditional complex laboratory procedures for MS analysis of biological samples.

Development of miniature mass spectrometry systems for bioanalysis outside the conventional laboratories.

Mass spectrometry (MS) is known for highly specific and sensitive analysis. The general applicability of this technique makes it a good candidate for biological applications over a much broader range than is now the case. The limiting factors preventing MS from being applied at the biologist's bench or in a physician's office are identified as the large size of the systems, as well as the complicated analytical procedures required. An approach for developing miniature MS analysis systems with simplified operational procedures is described and the associated technical developments are discussed.

Cation-induced stabilization of protein complexes in the gas phase: mechanistic insights from hemoglobin dissociation studies.

Collision-induced dissociation (CID) of electrosprayed protein complexes usually involves asymmetric charge partitioning, where a single unfolded chain gets ejected that carries a disproportionately large fraction of charge. Using hemoglobin (Hb) tetramers as model system, we confirm earlier reports that bound metal ions can stabilize protein complexes under CID conditions. We examine the mechanism underlying this effect. Nonvolatile salts cause extensive adduct formation. Significant stabilization was observed for Mg(2+) and Ca(2+), whereas K(+), Rb(+), and Cs(+) had no effect. Precursor ion selection was used to examine Hb subpopulations with well-defined metal binding levels. K(+), Rb(+), and Cs(+)-adducted tetramers eject monomers that carry roughly one-quarter of the metal ions that were bound to the precursor. This demonstrates that charge migration during CID is exclusively due to proton transfer, not metal ion transfer. Also, replacement of highly mobile charge carriers (protons) with less mobile species (metal ions) does not exert a stabilizing influence under the conditions used here. Interestingly, Hb carrying stabilizing ions (Mg(2+) and Ca(2+)) generates monomeric CID products that are metal depleted. This effect is attributed to a combination of two factors: (1) Me(2+) binding stabilizes Hb via formation of chelation bridges (e.g., R-COO(-) Me(2+) (-)OOC-R); the more Me(2+) a subunit contains the more stable it is. (2) More than ~90% of the tetramers contain at least one subunit with a below-average number of Me(2+). The prevalence of monomeric CID products with depleted Me(2+) levels is caused by the tendency of these low metal-containing subunits to undergo preferential unfolding/ejection.

Direct Mass Spectrometry Analysis of Untreated Samples of Ultralow Amounts Using Extraction Nano-Electrospray.

Direct mass spectrometry analysis of untreated samples of volumes as low as 0.2 µL were achieved using fast extraction and nanoESI (electrospray ionization) in a combined fashion. The analytes in dried samples on paper substrates were extracted by organic solvent in a nanoESI tube and ionized with a high voltage applied for generating a spray. The ionization source produced stable signals for different atmospheric pressure interfaces of triple quadrupole instruments. Analysis time more than 20 minutes were available with 10 µL solvent consumed for the entire analysis process. The performance in qualitative and quantitative analysis was characterized with a wide variety of samples. Limits of detection as low as 0.1 ng/mL (corresponding to an absolute amount of 0.05 pg) were obtained for analysis of atrazine in river water, thiabendazole in orange homogenate, and methamphetamine in blood.

Analysis of Biological Samples Using Paper Spray Mass Spectrometry: An Investigation of Impacts by the Substrates, Solvents and Elution Methods.

Paper spray has been developed as a fast sampling ionization method for direct analysis of raw biological and chemical samples using mass spectrometry (MS). Quantitation of therapeutic drugs in blood samples at high accuracy has also been achieved using paper spray MS without traditional sample preparation or chromatographic separation. The paper spray ionization is a process integrated with a fast extraction of the analyte from the raw sample by a solvent, the transport of the extracted analytes on the paper, and a spray ionization at the tip of the paper substrate with a high voltage applied. In this study, the influence on the analytical performance by the solvent-substrate systems and the selection of the elution methods was investigated. The protein hemoglobin could be observed from fresh blood samples on silanized paper or from dried blood spots on silica-coated paper. The on-paper separation of the chemicals during the paper spray was characterized through the analysis of a mixture of the methyl violet 2B and methylene blue. The mode of applying the spray solvent was found to have a significant impact on the separation. The results in this study led to a better understanding of the analyte elution, on-paper separation, as well as the ionization processes of the paper spray. This study also help to establish a guideline for optimizing the analytical performance of paper spray for direct analysis of target analytes using mass spectrometry.

Enabling quantitative analysis in ambient ionization mass spectrometry: internal standard coated capillary samplers.

We describe a sampling method using glass capillaries for quantitative analysis of trace analytes in small volumes of complex mixtures (~1 µL) using ambient ionization mass spectrometry. The internal surface of a sampling glass capillary was coated with internal standard then used to draw liquid sample and so transfer both the analyte and internal standard in a single fixed volume onto a substrate for analysis. The internal standard was automatically mixed into the sample during this process and the volumes of the internal standard solution and sample are both fixed by the capillary volume. Precision in quantitation is insensitive to variations in length of the capillary, making the preparation of the sampling capillary simple and providing a robust sampling protocol. Significant improvements in quantitation accuracy were obtained for analysis of 1 µL samples using various ambient ionization methods.

Quantitative paper spray mass spectrometry analysis of drugs of abuse.

An ambient method for rapid monitoring and quantitation of drugs of abuse in dried blood spots was developed using paper spray tandem mass spectrometry (PS-MS).

Mass spectrometry imaging for biomedical applications.

The development of technologies for mass spectrometry imaging is of substantial research interest. Mass spectrometry is potentially capable of providing highly specific information about the distribution of compounds in tissues, with high sensitivity. The in-situ analysis needed for tissue imaging requires MS to be performed under conditions different from the traditional ones, typically with intensive sample preparation and optimized for pharmaceutical applications. In this paper we critically review the current status of MS imaging with different methods of sample ionization and discuss the 3D and quantitative imaging capabilities which need further development, the importance of the multi-modal imaging, and the balance between the pursuit of high-resolution imaging and the practical application of MS imaging in biomedicine.

Assembly of hemoglobin from denatured monomeric subunits: heme ligation effects and off-pathway intermediates studied by electrospray mass spectrometry.

The oxygen binding properties of vertebrate hemoglobins (Hb) have been explored in great detail. In contrast, folding and assembly of these heterotetrameric protein complexes remain poorly understood. Similar to investigations of other multisubunit systems, in vitro Hb refolding experiments are often plagued by aggregation. Here we monitor the refolding of bovine Hb by electrospray mass spectrometry (ESI-MS). This technique allows the observation of coexisting subunit combinations, heme binding states, and protein conformers. Exposure to 40% acetonitrile at pH 10 causes Hb disassembly and extensive subunit unfolding. Hb reassembly is triggered by solvent exchange. Experiments conducted at room temperature provide a low metHb refolding yield. A significantly improved yield is achieved by lowering the temperature to 4 °C and by supplementing the protein solution with KCN prior to denaturation. Comparative studies under "low-yield" and "high-yield" conditions report on the interplay between folding and misfolding. The tendency of ß-globin to undergo aggregation is found to be the key impediment to the formation of native Hb. The α/ß imbalance generated in this way favors the formation of non-native α-globin assemblies. Our data imply that hemin dicyanide formed in the presence of KCN remains weakly bound to denatured ß-globin, thereby counteracting aggregation, such that the refolding yield is enhanced. In the absence of aggregation-related interference, Hb assembly follows a symmetric pathway. Monomeric α- and ß-globin adopt a compact conformation upon heme binding. Heme-bound monomers then form heterodimers, and ultimately heterodimer association results in native Hb. This work highlights the utility of time-resolved ESI-MS investigations for interrogating the kinetic competition between on-pathway events and aberrant side reactions during the self-assembly of biomolecular complexes.