PDMS Layer Research Articles

Silver-Hydrogel/PDMS film with high mechanical strength for anti-interference strain sensor

Hydrogels have recently emerged as promising candidates for wearable strain sensors. However, their poor mechanical stability and fragility limited their applications in many fields. Inspired by the skins, we developed a double-layer structured silver-Hydrogel/PDMS composite film (Ag-Hydrogel/PDMS) by chemically bonding the PDMS with a conductive Ag-Hydrogel layer. After assembled with the zinc, air electrodes and a fixed resistor, a self-powered Ag-Hydrogel/PDMS strain sensor was obtained. The mechanical properties of the Ag-Hydrogel/PDMS strain sensor was significantly enhanced due to the chemically bonded PDMS film. Compared to PDMS and Ag-Hydrogel alone, the tensile stress of Ag-Hydrogel/PDMS composite film increased by 3.4 and 58.1 times, respectively. The prepared Ag-Hydrogel/PDMS composite film could easily lift a 1050 g item without obviously interfacial failure. And it could output different voltage signals upon various finger motions without any external power supplies. Interestingly, the inert nature of PDMS also greatly improved the anti-interference property of the Ag-Hydrogel/PDMS strain sensor, as it protected the Ag-Hydrogel from the complicated environments. Moreover, excellent antibacterial activity of the Ag-Hydrogel/PDMS strain sensor against both of the E. coli and S. aureus bacteria was observed, which could be ascribed to the distribution of Ag nanocubes in the hydrogel matrix. The hydrophobic property of the PDMS layer further entitled the Ag-Hydrogel/PDMS strain sensor with a good bacterial anti-adhesion property. These characteristics guarantee the self-powered Ag-Hydrogel/PDMS strain sensor with potential application as wearable and portable electronic devices in complicated environments.

Synergistically Microstructured Flexible Pressure Sensors with High Sensitivity and Ultrawide Linear Range for Full‐Range Human Physiological Monitoring

AbstractHigh sensitivity and wide linear range are core performances for flexible pressure sensors in practical applications. Due to the trade‐off between sensitivity and linear range, developing high‐performance flexible pressure sensors with both high sensitivity and wide linear range through a facile method is still a great challenge. Herein, a synergistically microstructured flexible pressure sensor with fibrous and microdomed (FMD) structure composed of a fibrous conductive layer sandwiched between a microdome‐structured PDMS layer and an interdigital electrode is proposed. Ascribed to the synergistic effect of the FMD structure possessing multiple deformations, the resistance of the sensor varies sensitively and continuously under pressure. Consequently, the pressure sensors perform a high sensitivity (6.31 kPa−1), an ultrawide linear range (4.6 Pa–800 kPa), short response time (72 ms) and relaxation time (88 ms), and remarkable stability during 10 000 loading/unloading cycles under 127.4 kPa. These high performances allow the sensors to detect full‐range human psychological signals from low to high pressures, such as pulse, phonation, joint moments, and plantar pressure. Moreover, the synergistically microstructured sensors can be integrated into large‐area and crosstalk‐free sensor array to map the spatial pressure distribution, demonstrating their viable applications in personal physiological parameters monitoring and human–machine interfaces.

Transparent and durable PDMS(O)/HDTMS anti-icing surfaces derived from candle soot

Preventing icing on exposed surfaces is important in our daily life. However, the transparent and durable anti-icing coating is still a challenge. In this work, we demonstrated a transparent oxidized polydimethylsiloxane/hexadecyltrimethoxysilane (PDMS(O)/HDTMS) coating on slide by using the candle soot (CS) as a sacrificial template. The CS as a product of incomplete combustion of candles with a porous network chain structure was firstly deposited on the PDMS coated slide. After a calcination treatment, the CS was removed while the PDMS layer was oxidized and inherited the unique structure of the CS and became transparent and superhydrophilic. With the help of the HDTMS modification, the final PDMS(O)/HDTMS coating exhibited surperhydrophobic property (WCA = 163°, SA < 1°). The coating can preserve its surperhydrophobic state after different mechanical abrasion, acid/base, UV light exposure and icing/thawing cycles. Beneficial from its surperhydrophobic feature, the coating not only postponed the freezing time of the water droplet from 229 to 1022 s, but also enabled the ice slide away by gravity. In addition, the PDMS(O)/HDTMS was successfully used on the glass insulator to delay the ice accumulation. This work provides a facile and environmentally-friendly method to obtain transparent and durable anti-icing coating.

Cauliflower-like micro-nano structured superhydrophobic surfaces for durable anti-icing and photothermal de-icing

Ice formation and accretion have a severe negative impact, thus creating the tremendous demand for anti-icing/deicing surfaces. Compared with other techniques, superhydrophobic surfaces possess unique advantages including extremely low affinity to water droplets and reduced ice adhesion strength, whereas their weak durability and failure in cold and moist environments restrict their practical applications. Therefore, photothermal superhydrophobic surfaces possessing high light absorptivity have been proposed, by which ice can be removed by harvesting solar energy as heat eco-friendly and efficiently. However, practical photothermal superhydrophobic surfaces with superior photothermal capability, anti-icing/deicing performance and high durability remain scarce. In this study, a durable cauliflower-like micro-nano structured superhydrophobic surface was produced by combining the ultrafast laser ablation and wet chemical reactions. The hierarchical structures, composed of microcones arrays, in-situ grown cauliflower-like structure and closely bonded PDMS layer, exhibited not only a high absorption rate of 97.3%, but also the high durability in both experimental and natural environment. The temperature raised 48.5 °C under 1 sun illumination for 300 s in ambient conditions. The surface still kept superhydrophobic after several durability tests. The photothermal effect dramatically reduced the ice adhesion strength and deteriorations on the surface during its operation. Under the light intensity of 1 sun for 1 min each cycle, the ice adhesion strength maintained around 10 kPa stably over 40 icing-deicing cycles and the ice layer was melted under 2 min irradiation. Besides, in a three-month long outdoor experiment, the proposed superhydrophobic surface remained its efficient photothermal conversion capacity as well as high durability. Therefore, the cauliflower-like micro-nano structured superhydrophobic surface is one of the most promising methods for anti-icing/deicing applications due to the advantages of superior photothermal capability, long-term durability and adaptability.

Multifunctional recycled carbon fiber-Ti3C2Tx MXene paper with superior electromagnetic interference shielding and photo/electro-thermal conversion performances

The electromagnetic wave irradiation has obstructed the precise operation of the high-tech electronic equipment and threatened the health of the bodies during the 5G era. It is critical to develop electromagnetic interference (EMI) shielding materials with remarkable shielding effectiveness along with lightweight and flexible properties, while the integrations of the heat management performances have been gradually indispensable, especially in wearable electronic device applications. Anchoring the Ti3C2Tx MXene nanosheets on the surfaces of the recycled carbon fibers (RCF) and assembling heterostructure can be regarded as effective strategies, while simultaneously solving the conductivity reduction and the corresponding performance degradation bottlenecks of the thermal-recycling carbon fiber. The construction of the RCF-MXene paper performs remarkable EMI shielding performance of 45.7 dB, while the specific SE/t can be improved to 7723.85 dB cm2 g-1, along with impressive photothermal and electrothermal conversion abilities. After coating PDMS layers, the flexible RCF-MXene@PDMS film maintains stable EMI shielding performance when experiencing in-situ electrothermal conversion and after 10000-cycle mechanical deformation processes. Exhibiting multifunctionality by facile synthesis strategies, the RCF-MXene-based materials provide great potential as next-generation candidates in wearable electronic devices, together with promoting the advancement of the sustainable reuse of the carbon fibers resources.

Highly sensitive and superhydrophobic fabric sensor based on AgNPs/Polypyrrole composite conductive networks for body movement monitoring

Fabric sensors due to favorable flexibility and comfortability have remarkable progress in wearable sensing electronics recently, but it is enormous challenge to achieve broad sensing range, high sensitivity, stable sensing capability and great hydrophobicity for their practical applications. Herein, a highly sensitive and superhydrophobic strain sensor based on conductive polydimethylsiloxane/Ag nanoparticles/polypyrrole/nylon strip (PDMS/AgNPs/PPy/NS) is successfully fabricated via constructing AgNPs/PPy composite conductive networks on elastic NS, and then coating a thin protective layer (PDMS). The AgNPs/PPy composite conductive networks render the PDMS/AgNPs/PPy/NS large ΔR/R0 scale, and the assembled PDMS/AgNPs/PPy/NS strain sensor presents broad sensing range (0.1%–70%), high Gauge Factor value of 1.61 × 103 (with the strain range from 60% to 70%), ultralow detection limit (0.1% strain), fast response time (70 ms) and satisfying sensing stability (5000 cycles). The protective PDMS layer not only endows PDMS/AgNPs/PPy/NS strain sensor with excellent superhydrophobicity (WCA = 156°), but also improves the stability of sensor for daily use. Owing to the high sensitivity and excellent superhydrophobicity, PDMS/AgNPs/PPy/NS strain sensor can monitor various joint motions (throat, neck, elbow, wrist, knee and finger) and even work in harsh conditions (moisture, acid, alkaline and salt environment). In addition, PDMS/AgNPs/PPy/NS with low resistance (1.09 Ω cm−1) displays an outstanding electrothermal temperature (87.4 °C at 2.0 V). These remarkable performances demonstrate great potential of PDMS/AgNPs/PPy/NS in wearable electronics such as sensors and heaters.

Conductive and superhydrophobic Ag/PDMS films with high stability for passive de-icing and electromagnetic shielding

In this work, silver nanoparticles (AgNPs) are synthesized and sprayed onto the surface of cotton fabric to produce a conductive film. Then a layer of poly(dimethyl siloxane) (PDMS) was deposited onto the film to prepare Ag/PDMS composite film. The Ag film is with FCC crystalline and particle-like morphology, while layers of organic PDMS are cladding the Ag micro-nano structures. With increasing spraying time, nano‑silver particles changed from round spherical to worm-like, resulting rougher and higher electrical conductivity. By optimizing the PDMS coatings, the contact angle of surface winkled-like microstructure reached 163° and volume resistivity was 9.2 × 10−3 Ω·cm. In addition to the improvement of interfacial adhesion, the introduction of PDMS made the loose particles closely connected, which enhanced the stability of the structure. Meanwhile, the films exhibited great electron-thermal effects, which could be applied in high-speed deicing. Combined with superhydrophobicity, the electromagnetic shielding efficiency can reach 75 dB. The Ag/PDMS films maintained high electromagnetic shielding effectiveness even for servicing in harsh environments, showing that this conductive superhydrophobic fabric composite can be applied as a new electromagnetic shielding material for flexible electronic devices.

Silicalite-1/PDMS Hybrid Membranes on Porous PVDF Supports: Preparation, Structure and Pervaporation Separation of Dichlorobenzene Isomers.

Separation of dichlorobenzene (DCB) isomers with high purity by time− and energy−saving methods from their mixtures is still a great challenge in the fine chemical industry. Herein, silicalite-1 zeolites/polydimethylsiloxane (PDMS) hybrid membranes (silicalite-1/PDMS) have been successfully fabricated on the porous polyvinylidene fluoride (PVDF) supports to first investigate the pervaporation separation properties of DCB isomers. The morphology and structure of the silicalite-1 zeolites and the silicalite-1/PDMS/PVDF hybrid membranes were characterized by XRD, FTIR, SEM and BET. The results showed that the active silicalite-1/PDMS layers were dense and continuous without any longitudinal cracks and other defects with the silicalite-1 zeolites content no more than 10%. When the silicalite-1 zeolites content exceeded 10%, the surfaces of the active silicalite-1/PDMS layers became rougher, and silicalite-1 zeolites aggregated to form pile pores. The pervaporation experiments both in single-isomer and binary−isomer systems for the separation of DCB isomers was further carried out at 60 °C. The results showed that the silicalite-1/PDMS/PVDF hybrid membranes with 10% silicalite-1 zeolites content had better DCB selective separation performance than the silicalite-1/α−Al2O3 membranes prepared by template method. The permeate fluxes of the DCB isomers increased in the order of m−DCB < o−DCB < p−DCB both in single-isomer and binary-isomers solutions for the silicalite-1/PDMS/PVDF hybrid membranes. The separation factor of the silicalite-1/PDMS/PVDF hybrid membranes for p/o−DCB was 2.9 and for p/m−DCB was 4.6 in binary system. The permeate fluxes of the silicalite-1/PDMS/PVDF hybrid membranes for p−DCB in p/o−DCB and p/m−DCB binary−isomers solutions were 126.2 g∙m−2∙h−1 and 104.3 g∙m−2∙h−1, respectively. The thickness−normalized pervaporation separation index in p/o−DCB binary−isomers solutions was 4.20 μm∙kg∙m−2∙h−1 and in p/m−DCB binary−isomers solutions was 6.57 μm∙kg∙m−2∙h−1. The results demonstrated that the silicalite-1/PDMS/PVDF hybrid membranes had great potential for pervaporation separation of DCB from their mixtures.

Liquid–liquid interface induced PDMS‐PTFE composite membrane for ethanol perm‐selective pervaporation

AbstractPervaporation has great potential in the separation of many significant mixtures. However, excessive penetration of separation layer into the substrate pores enhances the transport resistance of solvent molecules, which impedes the development of pervaporation membrane. In this study, a facile floating‐on‐water (FOW) method was used to prepare poly(dimethylsiloxane) (PDMS)/polytetrafluoroethylene (PTFE) composite membranes. The formation of separation layer and preparation of composite membrane were step‐by‐step completed through this liquid–liquid interface induced method. The PDMS layer thickness could be precisely regulated from 0.5 to 8 μm. Moreover, the pore penetration could be controlled by optimizing pre‐crosslinking density, crosslinking time on water and polymer solution volume. The obtained PDMS/PTFE composite membrane exhibited a high flux of 2016 g·m−2·h−1 with the separation factor of 12 when separating ethanol from a 5 wt% ethanol/water mixture. The performance of the membrane could be stable for over 200 h, exhibiting great potential in ethanol perm‐selective pervaporation.

Design and modeling of a graphene-based composite structure optical pressure sensor.

In this paper, a novel graphene-based composite structure optical pressure sensor is designed and built with the aid of modeling. A PDMS force-sensitive structural mechanics model is established to optimize the size of the pyramid array distributed on the PDMS layer so that to support high levels of sensitivity and stability. Meanwhile, a graphene waveguide optical model is established to obtain the optimized interference length (L), arm spacing (H) and core width (W), with the objectives of advanced sensitivity, low propagation loss, high resolution. The experimental results show that the pressure sensitivity of the proposed sensor is 17.86 nm/kPa and the maximum pressure that can be detected is 3.40 kPa, which is consistent with the theoretical analysis and verifies the feasibility of the design, also the modeling methods of the graphene-based composite structure optical pressure sensor.

Fabrication of Stretchable Superamphiphobic Surfaces with Deformation-Induced Rearrangeable Structures.

Stretchable superamphiphobic surfaces with a high deformation resistance are in demand to achieve liquid-repellent performance in flexible electronics, artificial skin, and textile dressings. However, it is challenging to make mechanically robust superamphiphobic coatings, which maintain their superliquid repellency in a highly stretched state. Here, a stretchable superamphiphobic surface is reported, on which the microstructures can rearrange during stretching to maintain a stable superamphiphobicity even under a high tensile strain. The surface is prepared by spray-coating silicone nanofilaments onto a prestretched substrate (e.g., cis-1,4-polyisoprene) with poly(dimethylsiloxane) (PDMS) layer as a binder. After subsequent fluorination, this surface keeps its superamphiphobicity to both water and n-hexadecane up to the tensile strain of at least 225%. The binding PDMS layer and rearrangeable structures maximize the deformation resistance of the surface during the stretching process. The superamphiphobicity and morphology of the surface are maintained even after 1000 stretch-release cycles. Taking advantage of the mentioned benefits, a liquid manipulation system is designed, which has the potential for fabricating reusable and low-cost platforms for biochemical detection and lab-on-a-chip systems.

Ice-Shedding Polymer Coatings with High Hardness but Low Ice Adhesion

Ice readily sheds from weak oil-swollen polymer gels but tends to adhere to mechanically robust coatings. This paper reports bilayer coatings that simultaneously possess high bulk hardness but low ice adhesion. These coatings are prepared by cocuring a triisocyanate, P#'-g-PDMS [a methacrylate polyol bearing poly(dimethylsiloxane) (PDMS) side chains with # being 1, 2, or 3 and g denoting graft], and optionally a methacrylate polyol P#. The self-assembly of the system during coating formation yields a PDMS brush layer on the surface of the cross-linked polyurethane matrix. After the surface PDMS layer is lubricated with a silicone oil, this coating exhibits an ice adhesion τ that is 10 000-fold lower than that of a triisocyanate/P# coating. Ice slides under its own weight on such a coating at a tilt angle of 3°. Yet, the coating matrix is harder than poly(ethylene terephthalate), a widely used plastic. Additionally, such a coating maintains its low τ values for more than 10 consecutive icing/deicing cycles. Subsequent increases in τ are reversed by allowing time for the replenishment of the depleted surface lubricant with that released from the coating matrix. This design opens the door for effective yet hard ice-shedding polymer coatings.

Use of an elastic buffer layer for improved performance of a polymer microcylinder ring resonator hydrogen sensor

The impact of substrate on Pd nanofilm expansion in a Pd-H2 system is investigated using polymer microcylinder ring resonator (PMRR) platform. Being a highly sensitive platform for H2 gas detection, PMRR comprises of an inner sensitive Pd nanofilm and an outer PDMS layer coated on a standard optical fiber. Optical whispering gallery modes (WGMs) are excited in the rim of the outermost PDMS layer through evanescent field of a tapered fiber. H2 molecules penetrating the H2-sensitive Pd nanofilm through the PDMS layer cause reversible expansion in the PMRR. This translates into shifts in spectral positions of the WGMs that are observed with tapered fiber transmission spectroscopy. Two types of PMRRs were fabricated. In the first type, Pd nanofilm was directly deposited on the silica surface of an optical fiber. In the other one, a PDMS buffer layer was precoated between Pd nanofilm and the silica surface, with different thicknesses. It is demonstrated that, the use of a PDMS buffer layer yields higher radial expansion of the nanofilm during the interaction with H2 gas. A 180-nm-thick Pd nanofilm coated on ∼2.5-μm-thick PDMS buffer layer showed at least 18% higher radial expansion compared to the case without buffer layer. Identical thickness of Pd nanofilm on a ∼3.5-μm-thick PDMS buffer layer showed 30% higher radial expansion. Numerical and analytical calculations were also performed confirming the experimental results. Among mechanical properties of the PDMS buffer layer, Poisson’s ratio was found to be the most significant parameter affecting the expansion of the nanofilm.

“One for two” strategy of fully integrated textile based supercapacitor powering an ultra-sensitive pressure sensor for wearable applications

Textile-based energy storage devices help realize the full potential of flexible electronics as they combine the functionality of wearable devices with the inherent high-power density and fast charging/discharging capability of supercapacitors. In this work, Nickel di-selenide (NiSe2) is grown on carbon cloth (CC) via a facile one-pot hydrothermal technique and is used for supercapacitor and pressure sensor to demonstrate a textile-based fully integrated system. In a three-electrode configuration, the NiSe2 electrode produces a half-cell specific capacitance of 980 Fg−1 at 1 Ag−1, indicating its high-rate capability. Further, the NiSe2 electrode is combined with activated carbon (AC) electrodes generated from biomass to construct an asymmetric supercapacitor device (ASC) with a 1.6 V of output voltage. The ASC device delivers maximum specific energy of 50 Whkg−1 at a current density of 1 Ag−1 and a maximum specific power of 900 Wkg−1 at 10 Ag−1. An ultra-sensitive pressure sensor is fabricated by sandwiching the NiSe2 grown carbon cloth between thin layers of PDMS, which exhibits a sensitivity of 0.91 kPa−1 in the wide dynamic pressure range of 1– 80 kPa−1. An exceptional mechanical stability is obtained for an unloading/loading of 1 kPa of pressure for 5000 cycles. Further, it is powered using the NiSe2/CC || AC/CC AFSC for steady and reliable detection of radial pulse pressure on the human wrist in real-time. This work paves a new path in exploring the potential of textiles when combined with nanomaterials to develop low-cost, self-powered healthcare systems for real-time monitoring of health parameters.

Living algae detection with a PDMS-liquid chlorophyll fluorescence microfluidic chip filter and a smartphone.

Building an optical filtration function into a microfluidic chip is a promising way of simplifying the optical detection system of a microfluidic device. In this paper, a PDMS microfluidic chip filter that is capable of transmitting chlorophyll fluorescence and blocking interfering light in the visible wavelength range was developed for living algae detection with a smartphone. The chip was fabricated by sealing a layer of crystal violet solution in a PDMS layer on the top of the Sudan II-doped PDMS slab, which has a straight microchannel. Optimum dye concentrations and thicknesses for the crystal violet solution layer and Sudan II-doped PDMS slab were investigated and determined by spectrum measurements. It was found that the cut-on range of this integrated microfluidic chip is extended to about 625 nm and the transmittance in the chlorophyll fluorescence range (650 nm to 710 nm) is as high as 95%, when 25 mg L-1 Sudan II-doped PDMS slab (with a 3 mm thickness) and 2 mg L-1 crystal violet solution (with a 0.3 mm thickness) were used. Living algae detection using this chlorophyll-fluorescence-filtering PDMS microfluidic chip and a smartphone-based imaging platform was achieved, and the results compared favorably with those using a commercial filter.

A high-resolution electric field sensor based on piezoelectric bimorph composite

The rapid development of the internet of things technology has led to great demand for intelligent electric field sensor (EFS). Several working principles have been proposed, however major challenges remain existed for the requirements of EFS with low-cost, large-range, and high-resolution. In this paper, an EFS based on piezoelectric (PE) bending effect using d 31 mode is developed, where a bending strain is induced on the sandwiched bimorph structure of PZT/PDMS/PZT under an applied electric field, and the capacitance value of the PDMS layer reveals detectable variation. We demonstrate an EFS operating at the stress-mediated coupling between PE ceramic and elastic dielectric polymer, which reveals advantages such as simple fabrication process, low-cost and low power consumption. Due to the sandwiched bimorph structure, the strain caused by the electric field can be effectively transferred to improve the resolution of the device. The constitutive equations for the sandwiched bimorph structure are built, and the working principle of the proposed EFS is demonstrated. The EFS exhibits high sensitivity under both AC and DC electric fields, with a resolution of 0.1 V cm−1 in the range of −3 to 3 kV cm−1. The proposed sensor provides an alternative solution for power equipment fault diagnosis, power frequency electric field detection, etc.

Robust, Hyper-Permeable Nanomembrane Composites of Poly(dimethylsiloxane) and Cellulose Nanofibers.

Robust, nanometer-thick, permselective membranes were developed by composite formation from poly(dimethylsiloxane) (PDMS) and cellulose nanofibers (CNF). Their unique behavior is discussed in relation to that of a single-component PDMS nanomembrane. In the absence of the CNF component, the PDMS nanomembrane with a thickness of 34 nm displays ultrahigh permeability of CO2 gas, which is only ca. one order of magnitude smaller than that of free-flowing gases through a porous poly(acrylonitrile) support film (PAN, thickness 150 μm). The constant CO2/N2 selectivity observed for the whole range of membrane thickness (34 nm-10 μm) suggests that in the single-component membrane, the kinetic process at the membrane surface determines the permselective behavior. Multilayered composite membranes are obtainable by repeated spin coating. The mechanical weakness of the single-component PDMS membrane is improved by complexation with CNF, as confirmed by the bulge test and the ease of macroscopic handling. Such a robust PDMS-CNF nanomembrane gives superior permeation of 50,000 GPU with a defect-free PDMS layer of ca. 17 nm thickness. Interestingly, the permeation characteristics of the composite membrane are strongly affected by the asymmetric arrangement of PDMS and CNF layers, and the gas permeation from the side of the CNF layer is drastically reduced. The PDMS composite membrane is expected to provide practically useful systems as a means of direct air capture.

Porous PDMS conformable coating for high power output carbon fibers/ZnO nanorod-based triboelectric energy harvesters

A new method for depositing PDMS directly onto conductive carbon yarns is proposed to produce Triboelectric Nanogenerator Yarns (TENG yarns) that can serve as the basic building blocks for energy scavenging wearables. The in-situ PDMS curing method described in this study allows the fast formation of a uniform thick coating over conductive surfaces regardless of their roughness. Single-electrode configuration TENG yarns are developed and their electrical output is optimized by precisely adjusting the PDMS layer thickness and by changing the chemical and physical nature of the carbon fiber (CF) yarns’ surface. Functionalizing the CF yarns’ surface with ZnO rods combined with porous PDMS coating can enhance their electrical output. The best results are achieved using this type of TENG yarns with an average diameter of 1.74 mm, which can be obtained after only 3 min of PMDS deposition by “in-situ” curing method. A maximum of 72 V peak-to-peak and 10 µA (74.1 µW cm−2 of power density with a load resistance of 20 MΩ) is reached when applying an impact force of 600 N to a set of five TENG yarns connected in parallel. The output is stable even after 10,000 cycles and this set of TENG yarns is also able to light at least 28 LEDs when tapping by hand, proving a contribute towards the development of basic building blocks to power the future generation of wearables.

Miniaturized System for Tumor Cell Detection and Differentiation

This paper presents an automated, miniaturized, and portable system capable of detection and differentiation of cultured tumor cells and non-malignant cells. It is also capable of differentiation between single tumor cells and cell clusters. It is noninvasive, and operates without the need for cell labelling, device functionalization, and cell immobilization. The system is composed of a microfabricated electrical impedance spectroscopy (EIS) based sensor, a custom printed circuit board (PCB) and software running on a computer. The custom PCB replaces costly and specialized impedance analysis instruments and the software with a graphical user interface facilitates automated decisions - thus making the system easy to operate. Performance was tested with three human breast cell lines: healthy cell line BPE-3 and tumor cell lines MCF-7 and MDA-MB-231. The system successfully detected and differentiated between the three cell lines. The observed difference between the healthy cell line and the two tumor cell lines was more pronounced. And as cell detection and differentiation is based solely on biophysical properties of cells, disadvantages arising from affinity-based methods can be avoided. The presented miniaturized system possesses the potential to be developed into a low cost, portable and mass producible device for automated detection of CTCs in blood samples at point of care locations. The figure shows the microfabricated sensor consisting of a microfluidic channel with gold electrodes on the channel sidewalls employed to probe biological cells: (A) final device with PDMS layer to be bonded. (B) Microscope image of an electrode pair. (Scale bars 5mm and 100 μm).

Amino-functionalized ZIFs-based porous liquids with low viscosity for efficient low-pressure CO2 capture and CO2/N2 separation

Construct permanent porosity into liquids remains challenging, such as preparation, lower viscosity, economical, high-performance gas sorption, and separation. Herein, a general and economical surface engineering strategy has been implemented to construct a novel type Ⅰ porous liquids based on zeolitic imidazolate frameworks (denoted as ZIFs-based PLs) via covalently linking of amino-functionalized ZIFs with the diglycidyl ether-terminated of PDMS. The properties including free pore volume, viscosity, melting temperature (Tm), the gas capture, and CO2/N2 selective separation performance of PLs can be regulated by adjusting the pore structures, the amount of –NH2 introduced into ZIFs and molecular weight of the outer layers of PDMS, etc. Particularly, PLs1(1000)-5%, and PLs2(1000)-5% present viscosity values with 49 mPa⋅S-1 and 59 mPa⋅S-1 at 25 °C, to our best knowledge, which is the lowest viscosity of type I PLs reported previously. Meanwhile, Tm of PLs broke down to −78 °C, showing a wide liquid range. Remarkably, type Ⅰ PLs1(14000)-15.5% exhibits approximately 10 times higher CO2 uptake than that of the polymer in outer layers, which is attributed to the permanent free volume of ZIFs, chemistry sorption, and excellent liquidity. The CO2 breakthrough time of PLs for the CO2/N2 mixture was delayed for 53.7 s, confirming that PLs exhibits efficient CO2/N2 separation performance. Therefore, we envision that such a general and economical strategy will open new insights to construct innovative low viscosity type Ⅰ PLs with high-performance CO2 capture and CO2/N2 separation at low pressure.