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Miniaturized gas pumps based on electromagnetic effect have been intensively studied and widely applied in industries. However, the electromagnetic effect-based gas pumps normally have large sizes, high levels of noises and high power consumption, thus they are not suitable for wearable/portable applications. Herein, we propose a high-flowrate and high-pressure load valveless piezoelectric micropump with dimensions of 16 mm*16 mm*5 mm. The working frequency, vibration mode and displacement of the piezoelectric actuator, the velocity of gas flow, and the volume flowrate of the micropump are analyzed using the finite element analysis method. The maximum vibration amplitude of the piezoelectric actuator reaches ~29.4 μm. The output gas flowrate of the pump is approximately 135 mL/min, and the maximum output pressure exceeds 40 kPa. Then, a prototype of the piezoelectric micropump is fabricated. Results show that performance of the micropump is highly consistent with the numerical analysis with a high flowrate and pressure load, demonstrated its great potential for wearable/portable applications, especially for blood pressure monitoring., Competing Interests: Conflict of interestThe authors declare no competing interests., (© The Author(s) 2023.)

The performance of the Graphene/Si (Gr/Si) Schottky interface and its potential in future electronics strongly rely on the quality of interconnecting contacts with external circuitry. In this work, we investigate the dominating and limiting factors of Gr/Si interfaces designed for high light absorption, paying particular attention to the nature of the contact failure under high electrostatic discharge (ESD) conditions. Our findings indicate that severe current crowding at contact edges of the graphene is the dominating factor for the device breakdown. Material degradation and electrical breakdown are systematically analyzed by atomic force, Raman, scanning electron, and energy-dispersive x-ray spectroscopies. This work enlists the robustness and limitations of Gr/Si junction in photodiode architecture under high ESD conditions that can be used as general guidelines for 2D-3D electronic and optoelectronic devices., (© 2023 IOP Publishing Ltd.)

Sleep apnea syndrome (SAS) is a common but underdiagnosed health problem related to impaired quality of life and increased cardiovascular risk. In order to solve the problem of complicated and expensive operation procedures for clinical diagnosis of sleep apnea, here we propose a small and low-cost wearable apnea diagnostic system. The system uses a photoplethysmography (PPG) optical sensor to collect human pulse wave signals and blood oxygen saturation synchronously. Then multiscale entropy and random forest algorithms are used to process the PPG signal for analysis and diagnosis of sleep apnea. The SAS determination is based on the comprehensive diagnosis of the PPG signal and blood oxygen saturation signal, and the blood oxygen is used to exclude the error induced by non-pathological factors. The performance of the system is compared with the Compumedics Grael PSG (Polysomnography) sleep monitoring system. This simple diagnostic system provides a feasible technical solution for portable and low-cost screening and diagnosis of SAS patients with a high accuracy of over 85%.

DNA has been considered a promising alternative to the current solid-state devices for digital information storage. The past decade has witnessed tremendous progress in the field of DNA data storage contributed by researchers from various disciplines. However, the current development status of DNA storage is still far from practical use, mainly due to its high material cost and time consumption for data reading/writing, as well as the lack of a comprehensive, automated, and integrated system. Microfluidics, being capable of handling and processing micro-scale fluid samples in a massively paralleled and highly integrated manner, has gradually been recognized as a promising candidate for addressing the aforementioned issues. In this review, we provide a discussion on recent efforts of applying microfluidics to advance the development of DNA data storage. Moreover, to showcase the tremendous potential that microfluidics can contribute to this field, we will further highlight the recent advancements of applying microfluidics to the key functional modules within the DNA data storage workflow. Finally, we share our perspectives on future directions for how to continue the infusion of microfluidics with DNA data storage and how to advance toward a truly integrated system and reach real-life applications.

P(VDF-TrFE) is a promising material for flexible acoustic devices owing to its good piezoelectric performance and excellent stretchability. However, the high density of internal pores and large surface roughness of the conventional P(VDF-TrFE) results in a high propagation attenuation for acoustic waves, which limits its use in flexible acoustic devices. In this paper, a novel method based on two-step annealing is proposed to effectively remove the pores inside the P(VDF-TrFE) film and reduce its surface roughness. The obtained P(VDF-TrFE) film possesses excellent characteristics, including a high breakdown strength of >300 kV/mm, a high-purity β-phase content of more than 80%, and high piezoelectric coefficients (d 33 ) of 42 pm/V. Based on the low-porosity β-phase P(VDF-TrFE) film, we fabricated flexible film bulk acoustic resonators (FBARs) which exhibit high sharp resonance peaks. The pressure sensor was made by sandwiching the FBARs with two PDMS microneedle patches. Heartbeat and respiration rate monitoring were achieved using the pressure sensor. This work demonstrates the feasibility of high-performance flexible piezoelectric acoustic resonators based on low-porosity P(VDF-TrFE) films, which could see wider applications in the wearable sensors for both physical and chemical sensing.

Tendon injuries are some of the most commonly diagnosed musculoskeletal diseases. Tendon regeneration is sensitive to the topology of the substitute as it affects the cellular microenvironment and homeostasis. To bionic in vivo three-dimensional (3D) aligned microenvironment, an ordered 3D sandwich model was used to investigate the cell response in the tendon. First, high-resolution 3D printing provided parallel-grooved topographical cues on the hydrogel surface. Then the cells were seeded on its surface to acquire a 2D model. Afterward, an additional hydrogel coating layer was applied to the cells to create the 3D model. The interaction between cells and order structures in three-dimensions is yet to be explored. The study found that the tendon stem/progenitor cells (TSPCs) still maintain their ordering growth in the 3D model as in the 2D model. The study also found that the 3D-aligned TSPCs exhibited enhanced tenogenic differentiation through the PI3K-AKT signaling pathway and presented a less inflammatory phenotype than those in the 2D model. The in vivo implantation of such a 3D-aligned TSPC composite promoted tendon regeneration and mitigated heterotopic ossification in an Achilles defect model. These findings demonstrated that 3D-aligned TSPCs within a biomimetic topology environment are promising for functional tendon regeneration.

Active electrocorticogram (ECoG) electrodes can amplify weak electrophysiological signals and improve anti-interference ability; however, traditional active electrodes are opaque and cannot realize photoelectric collaborative observation. In this study, an active and fully transparent ECoG array based on zinc oxide thin-film transistors (ZnO TFTs) is developed as a local neural signal amplifier for electrophysiological monitoring. The transparency of the proposed ECoG array is up to 85%, which is superior to that of the previously reported active electrode arrays. Various electrical characterizations have demonstrated its ability to record electrophysiological signals with a higher signal-to-noise ratio of 19.9 dB compared to the Au grid (13.2 dB). The high transparency of the ZnO-TFT electrode array allows the concurrent collection of high-quality electrophysiological signals (32.2 dB) under direct optical stimulation of the optogenetic mice brain. The ECoG array can also work under 7-Tesla magnetic resonance imaging to record local brain signals without affecting brain tissue imaging. As the most transparent active ECoG array to date, it provides a powerful multimodal tool for brain observation, including recording brain activity under synchronized optical modulation and 7-Tesla magnetic resonance imaging., (© 2022 The Authors. Advanced Science published by Wiley-VCH GmbH.)

Solid-state nanopores play an important role in sensing single-biomolecules such as DNA and proteins. However, an ultra-short translocation time hinders nanopores from acquiring more detailed information about biomolecules, and further applications such as sequencing and molecular structure analysis are limited. Related studies have shown that MoS 2 has no obvious impediment to biomolecule translocation while graphene may cause obstacles to this process. By combining these two-dimensional materials, nanopores might slow the biomolecule passage. Herein, we fabricated sub-10 nm ultra-thin MoS 2 -graphene heterostructure nanopores with high stability and tested both dsDNA and native protein (BSA) at the single-molecule level in experiments for the first time. Some special signals with advanced order are observed, which may reflect the shape change of the BSA molecules during the slow translocation process. The results show that the translocation time of BSA is slowed down up to more than 100 ms and the signal length and form are determined by the extent of interaction between the BSA and the heterostructure nanopore. The weak interaction between the BSA and the MoS 2 layer increases the translocation probability, and meanwhile, the strong interaction of the graphene layer to BSA slows down the translocation and changes its structure. Therefore, our findings indicate the possibilities of slowing down the single-biomolecule translocation and the capability of acquiring more detailed information about biomolecules using MoS 2 -graphene heterostructure nanopores.

To meet the stringent requirements of 5G communication, we proposed a high-performance bulk acoustic wave (BAW) filter based on single crystal AlN piezoelectric films on a SiC substrate. The fabrication of the BAW filter is compatible with the GaN high electron mobility transistor (HEMT) process, enabling the implementation of the integration of the BAW device and high-performance monolithic microwave integrated circuit (MMIC). The single crystal AlN piezoelectric film with 650-nm thickness was epitaxially grown on the SiC substrate by Metal Organic Chemical Vapor Deposition (MOCVD). After wafer bonding and substrate removal, the single crystal AlN film with electrode layers was transferred to another SiC wafer to form an air gap type BAW. Testing results showed that the fabricated resonators have a maximum Q-factor up to 837 at 3.3 GHz resonant frequency and electromechanical coupling coefficient up to 7.2%. Ladder-type filters were developed to verify the capabilities of the BAW and process, which has a center frequency of 3.38 GHz with 160 MHz 3 dB bandwidth. The filter achieved a minimum 1.5 dB insertion loss and more than 31 dB out-of-band rejection. The high performance of the filters is attributed to the high crystallinity and low defects of epitaxial single crystal AlN films.

The triboelectric effect occurs when two dissimilar materials are in physical contact, attributed to the combination of contact electrification (CE) and electrostatic induction. It has been extensively explored for the development of high-performance triboelectric nanogenerators (TENGs). In this paper, we report on, besides the CE-related charge generation, an additional charge generation phenomenon associated with the modulation of the p-n junction when two semiconductor materials [methylammonium lead iodide (MAPI) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS)] are put in contact and separated dynamically. The electrical outputs generated by the CE effect are determined by the surface potential difference between the two friction materials, while the ones induced by the p-n junction modulation are determined by the dynamic variations in the depletion widths of the two semiconductor friction materials. The outputs generated by the CE effect and the p-n junction effect are well separated in time scale; the p-n junction modulation contributes ∼20% of the total charge generated and could be varied by changing the chemical composition of the semiconductors. The results may provide an alternative method for the development of high-performance TENGs by utilizing this additional p-n junction modulation effect.

A new silicon-controlled rectifier embedded diode (SCR-D) for 7 nm bulk FinFET process electrostatic discharge (ESD) protection applications is proposed. The transmission line pulse (TLP) results show that the proposed device has a low turn-on voltage of 1.77 V. Compared with conventional SCR and diode string, the proposed SCR-D has an additional conduction path constituting by two additional inherent diodes, which results in a 1.8-to-2.2-times current surge capability as compared with the simple diode string and conventional SCR with the same size. The results show that the proposed device meets the 7 nm FinFET process ESD design window and has already been applied in actual circuits.

Energy harvesting and energy transmission are the key technologies for self-powered systems; thus, the combination of these two is urgently needed. An innovative electric field resonance (EFR)-based wireless triboelectric nanogenerator (TENG) is proposed herein. By integrating the TENG with a capacitive coupler, the output of the TENG can be transmitted wirelessly from the transmitter to the receiver in the form of an oscillating signal with an energy-transfer efficiency of 67.8% for a 5 cm distance. Theoretical models of the EFR-TENG system are established, showing excellent agreement with the experimental results. It is demonstrated that the flexible EFR-TENG worn on the wrist can drive a digital watch wirelessly or light up at least 40 light-emitting diodes in series. The EFR-TENG is further utilized for spontaneous wireless sensing with a transmission distance up to 2.3 m with high system tolerance, showing the great potential of this novel strategy for energy harvesting and real-time wireless sensing applications.

Flexible surface acoustic wave (SAW) devices have recently attracted tremendous attention for their widespread application in sensing and microfluidics. However, for these applications, SAW devices often need to be bent into off-axis deformations between the acoustic wave propagation direction and bending direction. Currently, there are few studies on this topic, and the bending mechanisms during off-axis bending deformations have remained unexplored for multisensing applications. Herein, we fabricated aluminum nitride (AlN) flexible SAW devices by using high-quality AlN films deposited on flexible glass substrates and systematically investigated their complex deformation behaviors. A theoretical model was first developed using coupling wave equations and the boundary condition method to analyze the characteristics of the device with bending and off-axis deformation under elastic strains. The relationships between the frequency shifts of the SAW device and the bending strain and off-axis angle were obtained, and the results were identical to those from the theoretical calculations. Finally, we performed proof-of-concept demonstrations of its multisensing potential by monitoring human wrist movements at various off-axis angles and detecting UV light intensities on a curved surface, thus paving the way for the application of versatile flexible electronics., Competing Interests: Conflict of interestThe authors declare no competing interests., (© The Author(s) 2021.)

Here, we present integrated nanorod arrays on microfluidic chips for fast and sensitive flow-through immunoassays of physiologically relevant macromolecules. Dense arrays of Au nanorods are easily fabricated through one-step oblique angle deposition, which eliminates the requirement of advanced lithography methods. We report the utility of this plasmonic structure to improve the detection limit of the cardiac troponin I (cTnI) assay by over 6 × 10 5 -fold, reaching down to 33.9 fg mL -1 (~1.4 fM), compared with an identical assay on glass substrates. Through monolithic integration with microfluidic elements, the device enables a flow-through assay for quantitative detection of cTnI in the serum with a detection sensitivity of 6.9 pg mL -1 (~0.3 pM) in <6 min, which was 4000 times lower than conventional glass devices. This ultrasensitive detection arises from the large surface area for antibody conjugation and metal-enhanced fluorescent signals through plasmonic nanostructures. Moreover, due to the parallel arrangement of flow paths, simultaneous detection of multiple cancer biomarkers, including prostate-specific antigen and carcinoembryonic antigen, has been fulfilled with increased signal-to-background ratios. Given the high performance of this assay, together with its simple fabrication process that is compatible with standard mass manufacturing techniques, we expect that the prepared integrated nanorod device can bring on-site point-of-care diagnosis closer to reality., Competing Interests: Competing interestsThe authors declare no competing interests., (© The Author(s) 2021.)

Bioelectricity performs vital functions in the human body. When skin is damaged, the endogenous electric field will orient toward the center of wounds, guiding the migration of relevant cells and stimulating the secretion of growth factors. A large number of experiments have indicated that external electric stimuli have significant positive influences on wound healing. However, the mechanism of this therapy remains unclear, and the current selection of parameters for electric stimuli tends to be arbitrary or empirical, making it inefficient and ineffective. From the perspective of bioelectricity and electrochemistry, the mechanism of electric stimuli is investigated in detail based on a sectioned multilayer model in this work, and an electric stimuli window is obtained in terms of frequency, duty cycle, voltage, and electric charge and verified experimentally. This model provides general guidance for the optimization of electrical stimuli therapy for wound healing.

Background: Cryptosporidium is a protozoan parasite that can infect both humans and animals and cause cryptosporidiosis. We aimed to estimate the global prevalence of Cryptosporidium infection., Methods: In this study, Web of Science, Medline and PubMed were searched for relative articles, published between January 1, 1960 and January 1, 2018. Included articles were restricted to English language and that sample size of articles was not less than 50. Studies with no information on the study period, location, method of diagnosis, sample size and number of infected people were excluded. Studies about outbreak, laboratory report or immunocompromised population were excluded as well. The quality of the included publications was assessed. The prevalence of cryptosporidiosis was estimated by DerSimonian-Laird random-effects model, after converting by the Freeman-Tukey type double arcsine transformation., Findings: From 13,064 publications selected by literature search, 221 studies were included in the meta-analysis. The global pooled prevalence of Cryptosporidium infection was 7.6 % (95% CI: 6.9-8.5). The highest estimated prevalence of Cryptosporidium infection was in Mexico (69.6%, 95% CI 66.3-72.8), Nigeria (34.0%, 95% CI 12.4-60.0), Bangladesh (42.5%, 95% CI 36.1-49.0) and Republic of Korea (8.3%, 95% CI 4.4-13.2) among general residents, patients, school children and healthy population, respectively. The estimated prevalence was high in people from low-income country, people with gastrointestinal symptoms, people younger than 5 years old and residents not living in urban areas., Conclusions: These estimates indicate the substantial prevalence of Cryptosporidium infection in the world, which may provide a theoretical basis for the formulation of the prevention strategy about Cryptosporidium.

Objectives: Our objective was to determine the impact of maternal HIV-hepatitis B virus (HBV) coinfection on pregnancy outcomes., Methods: The current study was conducted in a county of Yi Autonomous Prefecture in southwest China. Data were abstracted from hospitalisation records, including maternal and infant information. The seroprevalences of HIV and HBV infections and HIV-HBV coinfection were determined and the impact of maternal HIV-HBV coinfection on adverse pregnancy outcomes was assessed using logistic regression analysis. A treatment effects linear regression model was also applied to examine the effect of HBV, HIV or coinfection to quantify the absolute difference in birth weight from a reference of HBV-HIV negative participants., Results: A total of 13 198 pregnant women were included in our study, and among them, 99.1% were Yi people and 90.8% lived in rural area. The seroprevalences of HIV and HBV infections and HIV-HBV coinfection were 3.6% (95% CI: 3.2% to 3.9%), 3.2% (95% CI: 2.9% to 3.5%) and 0.2% (95% CI: 0.1% to 0.2%) among the pregnant women, respectively. Maternal HIV-HBV coinfection was a risk factor for low birth weight (adjusted OR (aOR)=5.52, 95% CI: 1.97 to 15.40). Compared with the HIV mono-infection group, the risk of low birth weight was significantly higher in the HIV-HBV coinfection group (aOR=3.62, 95% CI: 1.24 to 10.56). Maternal HIV infection was associated with an increased risk of low birth weight (aOR=1.90, 95% CI: 1.38 to 2.60) and preterm delivery (aOR=2.84, 95% CI: 1.81 to 4.47). Perinatal death was more common when mothers were infected with HBV (aOR=2.85, 95% CI: 1.54 to 5.26)., Conclusions: The prevalence of HIV infection was high among pregnant women of the Yi region. Both HIV and HBV infections might have adverse effects on pregnancy outcomes. Maternal HIV-HBV coinfection might be a risk factor for low birth weight in the Yi region, which needs to be confirmed., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2020. No commercial re-use. See rights and permissions. Published by BMJ.)

The increased public concerns on healthcare, the environment and sustainable development inspired the development of biodegradable and biocompatible electronics that could be used as degradable electronics in implants. In this work, a fully biodegradable and flexible resistance random access memory (RRAM) was developed with low-cost biomaterial gelatin as the dielectric layer and the biodegradable polymer poly(lactide-coglycolide) acid (PLGA) as the substrate. PLGA can be synthesized by a simple solution process, and the PLGA substrate can be peeled off the handling substrate for operation once the devices are fabricated. The fabricated memory devices exhibited reliable nonvolatile resistive switching characteristics with a long retention time over 10 4 s and a near-constant on/off resistance ratio of 10 2 even after 200 bending cycles, showing the promising potential for application in flexible electronics. Degradation of the devices in deionized water and in phosphate buffered saline (PBS) solution showed that the whole devices can be completely degraded in water. The dissolution time of the metals and the gelatin layer was a few days, while that for PLGA is about 6 months, and can be modified by changing the synthesis conditions of the film, thus allowing the development of biodegradable electronics with designed dissolution time.

Here we demonstrate a magnetic resonance coupling based wireless triboelectric nanogenerator (TENG) and fully self-powered wireless sensors. By integrating a microswitch and an inductor with the TENG, the pulsed voltage output is converted into a sinusoidal voltage signal with a fixed frequency. This can be transmitted wirelessly from the transmit coil to the resonant-coupled receiver coil with an efficiency of 73% for a 5 cm distance between the two coils (10 cm diameter). Analytic models of the oscillating and coupled voltage signals for the wireless energy transfer are developed, showing excellent agreement with the experimental results. A TENG of 40 × 50 mm 2 can wirelessly light up 70 LEDs or charge up a 15 μF capacitor to 12.5 V in ~90 s. The system is further utilized for two types of fully self-powered wireless chipless sensors with no microelectronic components. The technologies demonstrate an innovative strategy for a wireless 'green' power source and sensing.

As a reliable indicator of human physiological health, respiratory rate has been utilized in more and more cases for prediction and diagnosis of potential respiratory diseases and the respiratory dysfunction caused by cystic fibrosis. However, compared with smart mobile electronics, traditional clinical respiration monitoring systems is not convenient to work as a household wearable device for real-time respiration monitoring in daily life due to its cumbersome structure, complex operability, and reliance on external power sources. Thus, we propose a wearable wireless respiration sensor based on lateral sliding mode triboelectric nanogenerator (TENG) to monitor respiratory rates by sensing the variation of the abdominal circumference. In this paper, we validate the possibility of the device as a respiration monitoring sensor via an established theoretical model and investigate the output performance of the sensor via a series of mechanical tests. Furtherly, the applications of the respiration sensor in different individuals, different breathing rhythms, different active states, and wireless transmission have been verified by a lot of volunteer tests. All the results demonstrate the potential of the proposed wearable sensor as a new alternative for detecting and monitoring real-time respiratory rates with general applicability and sensitivity.

Atomic layer deposited (ALD) ultra-thin alumina film is proposed to control the operational lifetimes of fully biodegradable (FB-) surface sensitive surface acoustic wave (SAW) devices. SAW devices encapsulated with conventional thick organic materials fail to function effectively, while devices with an ultra-thin alumina encapsulation layer (AEL) function normally with high performance. After being subjected to degradation in water, a FB-SAW device with no AEL starts to degrade immediately and fails within 8 h, due to dissolution of the tungsten electrode and piezoelectric material (ZnO). The coating of an ultra-thin AEL on the surfaces prevents SAW devices from undergoing degradation in water and enables SAW devices to perform normally before the AEL is dissolved. The stable operation lifetimes of SAW devices are linearly dependent on the AEL thickness, thus allowing for the design of devices with precisely controlled operational lifetimes and degradation times. The results show that all the materials used could be degraded; also, in vitro cytotoxicity tests indicate that the encapsulated FB-SAW devices are biocompatible, and cells can adhere and proliferate on them normally, demonstrating great potential for broader biodegradable electronic device applications.

Medical implantation of an electrocorticography (ECoG) recording system for brain monitoring is an effective clinical tool for seizure focus location and brain disease diagnosis. Planar and flexible ECoG electrodes can minimize the risks of infection and serious inflammatory response, and their good shape adaptability allows the device to fit complex cortex shape and structure to record brain signals with high spatial and temporal resolution. However, these ECoG electrodes require an additional surgery to remove the implant, which imposes potential medical risks. Here, a novel flexible and bioresorbable ECoG device integrated with an intracortical pressure sensor for monitoring swelling of the cortex during operation is reported. The ECoG device is fabricated with poly(l-lactide) and polycaprolactone composite and transient metal molybdenum. In vivo tests on rats show that the ECoG system can record the dynamic changes in brain signals for the different epilepsy stages with high resolution, while the malleable pressure sensor shows a linear relationship between the pressure and resistance in in vitro tests. In vitro degradation experiments show that the ECoG system can work stably for about five days before loss of efficacy, and the whole ECoG system degrades completely in a phosphate buffer solution in about 100 days., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Objective: Continuous measurement of key physiological parameters, such as heart rate (HR), pulse oxygen saturation (SpO 2 ), and sweat pH value, has very broad applications in healthcare, disease surveillance, and fitness and sports training. In this study, a stretchable optical sensing patch system was developed for real-time continuous noninvasive monitoring of the HR, SpO 2, and sweat pH, and the sensing data were transmitted to a smartphone through Bluetooth., Methods: The sensor patch system adopted serpentine stretchable interconnects between the optical sensor and microcontroller chip with wireless function on a flexible substrate. The pH sensing function was implemented by coating a pH sensitive organically modified silicate film on the surface of a commercial blood oxygen sensor, achieving simultaneous measurement of HR, SpO 2, and sweat pH with a single sensor., Results: Real-time on-body assessment was carried out to evaluate the sensor patch system, showing its excellent repeatability and applicability. The sensor patch system could withstand up to 35% extension and exhibited a pH sensitivity of 4.42 mV/pH from 4.0 to 8.0, while the accuracy of HR from 25 to 250 b/min and SpO 2 from 70% to 100% sensing were ±1 b/min and ±2%, respectively., Conclusion: The triple sensing functions was achieved through a single optical sensor on a flexible substrate while holding excellent contact with the body., Significance: The sensor patch system can be used for fitness guidance, skin disease detection, and wound monitoring and management by replacing related sensitive films.

Cryopreservation is essential to effectively extend the shelf life of delicate biomaterials while maintaining proper levels of cell functions. Cryopreservation requires a cryoprotective agent (CPA) to suppress intracellular ice formation during freezing, but it must be removed prior to clinical use due to its toxicity. Conventional multistep CPA loading and unloading approaches are time consuming, often creating osmotic shocks and causing mechanical injuries for biological samples. An efficient surface-acoustic-wave- (SAW-) based lab-on-a-chip (LoC) for fast loading and removal of CPAs is presented here. With the SAW-based multistep CPA loading/removal approach, high concentration (3 m) CPA can be successfully loaded and removed in less than 1 min. Results show that the technique causes the least harm to umbilical cord matrix mesenchymal stem cells as compared to conventional method, and an average of 24% higher cell recovery rate is achieved, while preserving the integrity and morphology of the cells. This device is the first of its kind to combine high loading/unloading efficiency, high cell viability, and high throughput into one LoC device, offering not only a more efficient and safer route for CPA loading and removal from cells, but also paving the way for other cryopreservation-dependent applications., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Stable and reliable electrical properties of interconnects and interfaces between flexible/stretchable and rigid materials/components are essential for the practical applications of flexible electronic devices and systems; traditional metal thin films and hard solder interconnects and interfaces can no longer meet these requirements. As an emerging soft conductive material, liquid metal has the advantages of high stretchability, flexibility, etc. over other soldering materials, and it has been used in interconnects and interfaces for some flexible electronics. In this study, we report a detailed investigation on the reliability and stability of liquid metal-based interconnects/interfaces under various mechanical deformations, including extension, bending, torsion, high frequency vibration and high temperature operation; we also compared the results with those of interconnects and interfaces using silver paste, the most commonly used solder for flexible electronics. The results show that liquid metal interconnects and interfaces maintain high conductivity under severe elongation up to 95% and 130%, upon bending with a curvature radius as low as ∼1.5 mm, and upon twisting up to 360°; meanwhile, interconnects and interfaces with silver paste filler lose electrical conductivity at elongations of 0.6% and 60%, respectively. Liquid metal interconnects and interfaces show superior performance to silver paste interconnects and interfaces because liquid metal can be re-shaped to make good contact with objects, while the silver paste becomes solid and rigid once dried and thus loses contact with other objects under deformation.

Similar to the gut, the bladder contains urinary microbiota, and its bacterial composition and structure are determined by the individual's health status. Cesarean section is a traumatic event for women and it is correlated with postpartum complications. To better understand the urinary microbiota alterations caused by cesarean section, 16S rDNA sequencing was used to assess urine specimens collected by transurethral catheterization from 30 healthy women undergoing cesarean section pre-delivery (PreD) and post-delivery (PostD). A significant increase in bacterial diversity and more detectable bacteria at the phylum, family, and genus levels was observed in the PostD group compared to the PreD group, indicating that cesarean delivery (a process that includes surgery and delivery) altered the bacterial community. Specifically, the phylum Firmicutes and its affiliated family Lactobacillaceae and genus Lactobacillus dramatically decreased in the PostD group, suggesting that beneficial bacteria decreased after cesarean section, and clinicians should be aware that this might increase the risk of complications. Concurrently, the phylum Proteobacteria and its affiliated bacteria Pseudomonadaceae and Pseudomonas increased in the PostD group compared to the PreD group. This indicates that pathogen growth increases after cesarean section, making it important for clinicians to combat these changes to protect women from infectious diseases. Interestingly, several metabolic pathways, such as metabolism of energy, cofactors and vitamins were strengthened in the PostD group, whereas membrane transport was lessened in this group. This suggests that women's metabolic disorders might be cured by balancing urinary microbiota. In conclusion, the altered urinary microbiota between the PreD and PostD periods appears to provide insight into how to prevent postpartum metabolic disorders.

Background : Intestinal parasitic infections pose great public health challenges in school children in developing countries. The aim of this study was to assess the prevalence of A. lumbricoides , T. trichiura and Cryptosporidium among elementary school children in rural southwestern China. Methods : A school-based cross-sectional study involving 321 elementary school children was conducted in 2014 in the southwest of China. They were invited to provide a stool sample and interviewed about the sanitary situation and hygiene behavior. Stool specimens were examined for A. lumbricoides and T. trichiura using the Kato-Katz fecal thick-smear technique. The presence of Cryptosporidium was determined using a modified acid-fast staining method. Results : The prevalence of infection was 10.0% (95% CI: 6.9⁻13.8%) for A. lumbricoides , 25.2% (95% CI: 20.6⁻30.4%) for T. trichiura and 2.4% for (95% CI: 1.1⁻4.9%) Cryptosporidium . The prevalence of co-infection was 3.7% (95% CI: 1.9⁻6.4%) for A. lumbricoides / T. trichiura , 0.3% (95% CI: 0⁻1.7%) for A. lumbricoides / Cryptosporidium and 0.9% (95% CI: 0.2⁻2.7%) for T. trichiura / Cryptosporidium . Children from households using well or river water were associated with a greater odds of A. lumbricoides infection (aOR = 2.61, 95% CI: 1.12⁻6.05). Having a household lavatory was associated with a lower odds of T. trichiura infection (aOR = 0.50, 95% CI: 0.30⁻0.84). Children who had three meals at the school canteen on week days were at a lower risk of Cryptosporidium infection. The use of spring water as a water source was associated with lower odds of any intestinal infection (aOR = 0.56, 95% CI: 0.35⁻0.91). Conclusions : Our study calls for an intervention program of school-based deworming combined with health education, hygiene promotion and provision of safe water and improved sanitation.

Developing soft devices for invasive procedures bears great importance for human health. The softness and large strain actuation of responsive hydrogels promise the potential to fabricate soft devices, which can attach on and assist to the function of organs. The key challenges lie in the fabrication of soft devices with robust actuating ability and biocompatibility to the attached organ. This paper presents a solution that integrates the thermoresponsive hydrogel membrane with flexible electronics and silk scaffold into a balloon-like soft device. As an example, the actuation assisting function of this soft device for shrinking an animal bladder is presented. The mechanical behaviors of the balloon-like soft device are experimentally and theoretically investigated. The concepts are applicable to other applications such as soft implants, soft robotics, and microfluidics., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A nanoscale insulator-based dielectrophoresis (iDEP) technique is developed for rapid enrichment of proteins and highly sensitive immunoassays. Dense arrays of nanorods (NDs) by oblique angle deposition create a super high electric field gradient of 2.6 × 10 24 V 2 m -3 and the concomitant strong dielectrophoresis force successfully traps small proteins at a bias as low as 5 V. 1800-fold enrichment of bovine serum albumin protein at a remarkable rate of up to 180-fold s -1 is achieved using oxide coated Ag nanorod arrays with pre-patterned sawtooth electrodes. Based on this system, an ultrasensitive immunoassay of mouse immunoglobulin G is demonstrated with a reduction in the limit of detection from 5.8 ng mL -1 (37.6 pM) down to 275.3 fg mL -1 (1.8 f M), compared with identical assays performed on glass plates. This methodology is also applied to detect a cancer biomarker prostate-specific antigen spiked in human serum with a detection limit of 2.6 ng mL -1 . This high sensitivity results from rapid biomarker enrichment and metal enhanced fluorescence through the integration of nanostructures. The concentrated proteins also accelerate binding kinetics and enable signal saturation within 1 min. Given the easy fabrication process, this nanoscale iDEP system provides a highly sensitive detection platform for point-of-care diagnostics., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Electrospinning is a simple, versatile technique for fabricating fibrous nanomaterials with the desirable features of extremely high porosities and large surface areas. Using emulsion electrospinning, polytetrafluoroethylene/polyethene oxide (PTFE/PEO) membranes were fabricated, followed by a sintering process to obtain pure PTFE fibrous membranes, which were further utilized against a polyamide 6 (PA6) membrane for vertical contact-mode triboelectric nanogenerators (TENGs). Electrostatic force microscopy (EFM) measurements of the sintered electrospun PTFE membranes revealed the presence of both positive and negative surface charges owing to the transfer of positive charge from PEO which was further corroborated by FTIR measurements. To enhance the ensuing triboelectric surface charge, a facile negative charge-injection process was carried out onto the electrospun (ES) PTFE subsequently. The fabricated TENG gave a stabilized peak-to-peak open-circuit voltage (V oc ) of up to ∼900 V, a short-circuit current density (J sc ) of ∼20 mA m -2 , and a corresponding charge density of ∼149 μC m -2 , which are ∼12, 14, and 11 times higher than the corresponding values prior to the ion-injection treatment. This increase in the surface charge density is caused by the inversion of positive surface charges with the simultaneous increase in the negative surface charge on the PTFE surface, which was confirmed by using EFM measurements. The negative charge injection led to an enhanced power output density of ∼9 W m -2 with high stability as confirmed from the continuous operation of the ion-injected PTFE/PA6 TENG for 30 000 operation cycles, without any significant reduction in the output. The work thus introduces a relatively simple, cost-effective, and environmentally friendly technique for fabricating fibrous fluoropolymer polymer membranes with high thermal/chemical resistance in TENG field and a direct ion-injection method which is able to dramatically improve the surface negative charge density of the PTFE fibrous membranes.

The future point-of-care diagnostics requires miniaturizing the existing bulky and expensive bioanalysis instruments, where lab-on-CMOS-chip-based technology can provide a promising solution. In this paper, we presented a surface acoustic wave (SAW) pumped lensless microfluidic imaging system for flowing cell detection and counting. Different from the previous lensless systems, which employ external bulky syringe pump for cell driven, the developed system directly integrates the SAW pump on the CMOS image sensor chip to drive the cell-containing microfluid. Moreover, an efficient temporal-differencing-based motion detection algorithm is proposed for continuous flowing cell detection and counting. Experimental results show that the SAW pump can drive the cells to flow at different driven powers, and also can keep the channel temperature below 40 °C so as not to harm the cells. The human bone marrow stromal cells flowing in the microfluidic channel can be automatically detected and counted with a low statistical error rate of -6.53%. The developed system thereby is competitive for point-of-care cell detection and counting application.

In this paper, we present a portable wireless electrocorticography (ECoG) system. It uses a high resolution 32-channel flexible ECoG electrodes array to collect electrical signals of brain activities and to stimulate the lesions. Electronic circuits are designed for signal acquisition, processing and transmission using Bluetooth Low Energy 4 (LTE4) for wireless communication with cell phone. In-vivo experiments on a rat show that the flexible ECoG system can accurately record electrical signals of brain activities and transmit them to cell phone with a maximal sampling rate of 30 ksampling/s per channel. It demonstrates that the epilepsy lesions can be detected, located and treated through the ECoG system. The wireless ECoG system has low energy consumption and high brain spatial resolution, thus has great prospects for future application.

High-performance photodetectors operating over a broad wavelength range from ultraviolet, visible, to infrared are of scientific and technological importance for a wide range of applications. Here, a photodetector based on van der Waals heterostructures of graphene and its fluorine-functionalized derivative is presented. It consistently shows broadband photoresponse from the ultraviolet (255 nm) to the mid-infrared (4.3 µm) wavelengths, with three orders of magnitude enhanced responsivity compared to pristine graphene photodetectors. The broadband photodetection is attributed to the synergistic effects of the spatial nonuniform collective quantum confinement of sp 2 domains, and the trapping of photoexcited charge carriers in the localized states in sp 3 domains. Tunable photoresponse is achieved by controlling the nature of sp 3 sites and the size and fraction of sp 3 /sp 2 domains. In addition, the photoresponse due to the different photoexcited-charge-carrier trapping times in sp 2 and sp 3 nanodomains is determined. The proposed scheme paves the way toward implementing high-performance broadband graphene-based photodetectors., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

After a decade of intensive research on two-dimensional (2D) materials inspired by the discovery of graphene, the field of 2D electronics has reached a stage with booming materials and device architectures. However, the efficient integration of 2D functional layers with three-dimensional (3D) systems remains a significant challenge, limiting device performance and circuit design. In this review, we investigate the experimental efforts in interfacing 2D layers with 3D materials and analyze the properties of the heterojunctions formed between them. The contact resistivity of metal on graphene and related 2D materials deserves special attention, while the Schottky junctions formed between metal/2D semiconductor or graphene/3D semiconductor call for careful reconsideration of the physical models describing the junction behavior. The combination of 2D and 3D semiconductors presents a form of p-n junctions that have just marked their debut. For each type of the heterojunctions, the potential applications are reviewed briefly.