Polydimethylsiloxane Membrane Research Articles

Flexible Au@Ag/PDMS SERS imprinted membrane combined with molecular imprinting technology for selective detection of MC-LR

In this study, a core–shell structured bimetallic nano-cube, Au@Ag NCs, was prepared by seed-mediated growth procedure. The array structure of Au@Ag NCs was achieved at the interface through the autonomous assembly technique at the three-phase boundary. Employing polydimethylsiloxane (PDMS) as a flexible carrier, the array structure was effortlessly transferred to the PDMS membrane, bypassing the need for rigid substrates through a simple “pasting” method. This yielded a highly flexible and transparent SERS substrate with an array structure (Au@Ag NCs/PDMS membrane, AAP). In order to promote the selective detection property to the practical samples, molecularly imprinted polymers (MIPs) were coated on the surface of membrane to prepare the imprinted membrane (Au@Ag NCs/PDMS-MIMs, AAP-MIMs). It was demonstrated from the results that the AAP-MIMs exhibited high SERS sensitivity, stability, and uniformity. Furthermore, the flexible substrate possessed commendable mechanical strength, and facilitated the detection of analytes on irregular surfaces. In summary, this substrate held promising potential for practical on-site detection and analysis of specific target substances.

Acoustic Waves Coupling with Polydimethylsiloxane in Reconfigurable Acoustofluidic Platform.

Acoustofluidics is a promising technology that leverages acoustic waves for precise manipulation of micro/nano-scale flows and suspended objects within microchannels. Despite many advantages, the practical applicability of conventional acoustofluidic platforms is limited by irreversible bonding between the piezoelectric actuator and the microfluidic chip. Recently, reconfigurable acoustofluidic platforms are enabled by reversible bonding between the reusable actuator and the replaceable polydimethylsiloxane (PDMS) microfluidic chip by incorporating a PDMS membrane for sealing the microchannel and coupling the acoustic waves with the fluid inside. However, a quantitative guideline for selecting a suitable PDMS membrane for various acoustofluidic applications is still missing. Here, a design rule for reconfigurable acoustofluidic platforms is explored based on a thorough investigation of the PDMS thickness effect on acoustofluidic phenomena: acousto-thermal heating (ATH), acoustic radiation force (ARF), and acoustic streaming flow (ASF). These findings suggest that the relative thickness of the PDMS membrane (t) for acoustic wavelength (λPDMS) determines the wave attenuation in the PDMS and the acoustofluidic phenomena. For t/λPDMS≈O(1), the transmission of acoustic waves through the membrane leads to the ARF and ASF phenomena, whereas, for t/λPDMS≈O(10), the acoustic waves are entirely absorbed within the membrane, resulting in the ATH phenomenon.

Thin microporous polydimethylsiloxane membrane prepared by phase separation and its applications for cell culture

Animal experiments are often required for biological studies. However, in vitro cell culture models, such as cell-culture inserts and microphysiological systems, can provide a suitable alternative, making them essential tools in cell biology research, including the simulation of an organ environments closely related to the human body. Cell-culture inserts with porous membranes assist in recreating in vivo cell culture environments to study and process cell-culture assays. However, conventional cell culture membranes typically made of polyethylene terephthalate or polycarbonate cannot accommodate cell types that require deformable substrates. As such, this paper introduced a novel approach using spin-casting-assisted polymer-blend phase separation to create thin, flexible, and highly porous membranes for cell culture applications. Polydimethylsiloxane (PDMS) was selected as the material for the porous membrane, and polystyrene (PS) was used as a counter pair to induce phase separation with PDMS. PDMS facilitated the necessary reversible deformations during cell culture owing to its low elastic modulus. The thickness of the membrane and connectivity of the phase-separated PS domains can be adjusted, facilitating the fine-tuning of the pore size and density to improve the membrane performance. Therefore, this study successfully fabricated thin microporous PDMS membranes with improved performance over standard membranes for cell-culture inserts, namely a higher porosity, flexibility, and softness. The results of this study can enhance cell culture methodologies and contribute to a deeper understanding of cellular processes.

A flexible strategy to fabricate trumpet-shaped porous PDMS membranes for organ-on-chip application.

Porous polydimethylsiloxane (PDMS) membrane is a crucial element in organs-on-chips fabrication, supplying a unique substrate that can be used for the generation of tissue-tissue interfaces, separate co-culture, biomimetic stretch application, etc. However, the existing methods of through-hole PDMS membrane production are largely limited by labor-consuming processes and/or expensive equipment. Here, we propose an accessible and low-cost strategy to fabricate through-hole PDMS membranes with good controllability, which is performed via combining wet-etching and spin-coating processes. The porous membrane is obtained by spin-coating OS-20 diluted PDMS on an etched glass template with a columnar array structure. The pore size and thickness of the PDMS membrane can be adjusted flexibly via optimizing the template structure and spinning speed. In particular, compared to the traditional vertical through-hole structure of porous membranes, the membranes prepared by this method feature a trumpet-shaped structure, which allows for the generation of some unique bionic structures on organs-on-chips. When the trumpet-shape faces upward, the endothelium spreads at the bottom of the porous membrane, and intestinal cells form a villous structure, achieving the same effect as traditional methods. Conversely, when the trumpet-shape faces downward, intestinal cells spontaneously form a crypt-like structure, which is challenging to achieve with other methods. The proposed approach is simple, flexible with good reproducibility, and low-cost, which provides a new way to facilitate the building of multifunctional organ-on-chip systems and accelerate their translational applications.

Electrochemical sintering of lithium metal constrained by buffer layer in anode-free all-solid-state batteries

Anode-free all-solid-state lithium-metal batteries hold promise in energy density. However, they often suffer from rapid capacity decay, and the underlying mechanisms remain unclear, especially at high current densities. Here, failure mechanism is studied systematically for garnet solid electrolyte in Li anode-free all-solid-state batteries. By combining morphology evolution analysis and quantitative assessments, the decreased Coulombic efficiency for solid electrolyte at high current densities is attributed to large amounts of lump-shaped lithium deposits via the electrochemical sintering. The lump-shaped lithium deposits encapsulate numerous voids and solid electrolyte interphase leading to irreversible capacities. Furthermore, serious pulverization of lithium deposits is observed after long cycles. An addition of polydimethylsiloxane membrane is attempted to constrain electrochemical sintering of lithium and compact lithium metal deposits, leading to prolonged cycling performance.

Development of a Microbioreactor for Bacillus subtilis Biofilm Cultivation.

To improve our understanding of Bacillus subtilis growth and biofilm formation under different environmental conditions, two versions of a microfluidic reactor with two channels separated by a polydimethylsiloxane (PDMS) membrane were developed. The gas phase was introduced into the channel above the membrane, and oxygen transfer from the gas phase through the membrane was assessed by measuring the dissolved oxygen concentration in the liquid phase using a miniaturized optical sensor and oxygen-sensitive nanoparticles. B. subtilis biofilm formation was monitored in the growth channels of the microbioreactors, which were designed in two shapes: one with circular extensions and one without. The volumes of these microbioreactors were (17 ± 4) μL for the reactors without extensions and (28 ± 4) μL for those with extensions. The effect of microbioreactor geometry and aeration on B. subtilis biofilm growth was evaluated by digital image analysis. In both microbioreactor geometries, stable B. subtilis biofilm formation was achieved after 72 h of incubation at a growth medium flow rate of 1 μL/min. The amount of oxygen significantly influenced biofilm formation. When the culture was cultivated with a continuous air supply, biofilm surface coverage and biomass concentration were higher than in cultivations without aeration or with a 100% oxygen supply. The channel geometry with circular extensions did not lead to a higher total biomass in the microbioreactor compared to the geometry without extensions.

A High-Quality Mixed Matrix Membrane with Nanosheets Assembled and Uniformly Dispersed Fillers for Ethanol Recovery.

A high-quality filler within mixed matrix membranes, coupled with uniform dispersity, endows a high-efficiency transfer pathway for the significant improvement on separation performance. In this work, a zeolite-typed MCM-22 filler is reported that is doped into polydimethylsiloxane (PDMS) matrix by ultrafast photo-curing technique. The unique structure of nanosheets assembly layer by layer endows the continuous transfer channels towards penetrate molecules because of the inter-connective nanosheets within PDMS matrix. Furthermore, an ultrafast freezing effect produced by fast photo-curing is used to overcome the key issue, namely filler aggregation, and further eliminates defects. When pervaporative separating a 5 wt% ethanol aqueous solution, the resulting MCM-22/PDMS membrane exhibits an excellent membrane flux of 1486g m-2 h-1 with an ethanol separation factor of 10.2. Considering a biobased route for ethanol production, the gas stripping and vapor permeation through this membrane also shows a great enrichment performance, and the concentrated ethanol is up to 65.6 wt%. Overall, this MCM-22/PDMS membrane shows a high separation ability for ethanol benefited from a unique structure deign of fillers and ultrafast curing speed of PDMS, and has a great potential for bioethanol separation from cellulosic ethanol fermentation.

Tape-assisted fabrication method for constructing PDMS membrane-containing culture devices with cyclic radial stretching stimulation.

Advanced in vitro culture systems have emerged as alternatives to animal testing and traditional cell culture methods in biomedical research. Polydimethylsiloxane (PDMS) is frequently used in creating sophisticated culture devices owing to its elastomeric properties, which allow mechanical stretching to simulate physiological movements in cell experiments. We introduce a straightforward method that uses three types of commercial tape-generic, magic and masking-to fabricate PDMS membranes with microscale thicknesses (47.2 µm for generic, 58.1 µm for magic and 89.37 µm for masking) in these devices. These membranes are shaped as the bases of culture wells and can perform cyclic radial movements controlled via a vacuum system. In experiments with A549 cells under three mechanical stimulation conditions, we analysed transcriptional regulators responsive to external mechanical stimuli. Results indicated increased nuclear yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) activity in both confluent and densely packed cells under cyclically mechanical strains (Pearson's coefficient (PC) of 0.59 in confluent and 0.24 in dense cells) compared with static (PC = 0.47 in confluent and 0.13 in dense) and stretched conditions (PC = 0.55 in confluent and 0.20 in dense). This technique offers laboratories without microfabrication capabilities a viable option for exploring cellular behaviour under dynamic mechanical stimulation using PDMS membrane-equipped devices.

Alternate solvent for soybean oil extraction based on extractability and membrane solvent recovery.

Ethyl acetate, acetone, 2-propanol, 1-propanol, and ethanol were screened among the class 3 category solvents as an alternative to hexane based on operational and occupational safety and bio-renewability potential. All five solvents exhibited higher extractability (22.3 to 23.2%) than hexane (21.5%) with soybean flour. Additionally, there was no significant difference in the fatty acid and triacylglycerol (TAG) composition of the oils extracted using alternate solvents and hexane, indicating the oil quality was not affected. More importantly, ethyl acetate (2.1%) resulted in a marginally higher yield of TAG, while 2-propanol showed a nearly equal yield to hexane. Further, membrane desolventizing was attempted to mitigate the limitations of higher thermal energy requirements. One of the polydimethylsiloxane membranes exhibited good selectivity (TAG rejection 85.8%) and acceptable flux (59.3 L·m-2·h-1) with an ethyl acetate miscella system. Under plant-simulated recirculation conditions, a two-stage membrane process reduced the oil content in permeate to 2.5%. The study revealed that ethyl acetate could potentially replace hexane, considering its higher TAG extractability and suitability for the membrane-augmented solvent recycling process in the extraction plants.

One-pot electrochemical detection of foodborne pathogen based on in situ nucleic acid amplification and wash-free assay.

Asignal amplification electrochemical biosensor chip was developed to integrate loop-mediated isothermal amplification (LAMP) based on in situ nucleic acid amplification and methyl blue (MB) serving as the hybridization redox indicator for sensitive and selective foodborne pathogen detection without a washing step. The electrochemical biosensor chip was designed by a screen-printed carbon electrode modified with gold nanoparticles (Au NPs) and covered with polydimethylsiloxane membrane to form a microcell. The primers of the target were immobilized on the Au NPs by covalent attachment for in situ amplification. The electroactive MB was used as the electrochemical signal reporter and embedded into the double-stranded DNA (dsDNA) amplicons generated by LAMP. Differential pulse voltammetry was introduced to survey the dsDNA hybridization with MB, which differentiates the specifically electrode-unbound and -bound labels without a washing step. Pyrene as the back-filling agent can further improve response signaling by reducing non-specific adsorption. This method is operationally simple, specific, and effective. The biosensor showed a detection linear range of 102-107CFUmL-1 with the limit of detection of 17.7CFUmL-1 within 40min. This method showed promise for on-site testing of foodborne pathogens and could be integrated into an all-in-one device.

Flexible Multicavity SERS Substrate Based on Ag Nanoparticle-Decorated Aluminum Hydrous Oxide Nanoflake Array for Highly Sensitive In Situ Detection.

Flexible surface-enhanced Raman scattering (SERS) substrates are very promising to meet the needs for real-time and on-field detection in practical applications. However, high-performance flexible SERS substrates often suffer from complexity and high cost in fabrication, limiting their widespread applications. Herein, we developed a facile method to fabricate a flexible multicavity SERS substrate composed of a silver nanoparticle (AgNP)-decorated aluminum hydrous oxide nanoflake array (NFA) grown on a polydimethylsiloxane (PDMS) membrane. Strong plasmon couplings promoted by multiple nanocavities afford high-density hotspots within such a flexible AgNPs@NFA/PDMS film, boosting high SERS sensitivity with an enhancement factor (EF) of ∼1.54 × 109, and a limit of detection (LOD) of ∼7.4 × 10-13 M for rhodamine 6G (R6G) molecules. Furthermore, benefiting from the high sensitivity, high mechanical stability, and transparency of this substrate, in situ SERS detections of trace thiram and crystal violet (CV) molecules on the surface of cherry tomatoes and fish have been realized, with LODs much lower than the maximum allowable limit in food, demonstrating the great potential of such a flexible substrate in food safety monitoring. More importantly, the preparation processes are very simple and environmentally friendly, and the techniques involved are completely compatible with well-established silicon device technologies. Therefore, large-area fabrication with low cost can be readily realized, enabling the extensive applications of SERS sensors in daily life.

Ethanol mass transfer model of spiral-wound membrane module with PDMS membrane for pervaporation considering module structure parameters

Pervaporation mass transfer model of spiral-wound membrane module with polydimethylsiloxane (PDMS) membrane considering module structure parameters has been developed for ethanol separation. Membrane intrinsic parameters involved mass transfer including limiting diffusivity of ethanol, plasticization coefficient of ethanol and partition coefficient were firstly determined, and then the model was verified by the experimental results with a correlation coefficient of 0.998. It has been calculated that bulk ethanol concentration (xe) would be decreased from 9 v/v% to 7.26 v/v% along the flow direction, under the ethanol feeding concentration of 9 v/v%, feeding velocity of 0.008 ms−1, membrane length of 1 m, membrane width of 1.5 m, channel height of 1.2 mm, if polydimethylsiloxane/polyamide (PDMS/PA) membrane was applied. Owing to the concentration-dependence of the membrane mass transfer coefficient (km), km and local ethanol flux (Je) was also decreased from 7.20 × 10-6 m·s-1to 7.07 × 10-6 m·s−1, and 386 g·m−2·h−1 to 306 g·m−2·h−1, respectively. For polydimethylsiloxane/polyvinylidene difluoride/Polyethylene terephthalate (PDMS/PVDF/PET) membrane, km and Je were decreased from 7.72 × 10-7 m·s-1to 7.65 × 10-7 m·s−1, and 137 g·m−2·h-1to 128 g·m−2·h−1, respectively, under the same condition. Higher ethanol feeding concentration and longer module would lead to more obvious change in xe, km and Je. While higher feeding velocity would lead to weaker change in xe, km and Je.

Enhancing butanol separation efficiency in pervaporation with ZIF-8 porous liquid infused mixed matrix membranes

Separating butanol/water mixtures via distillation is notably energy-intensive and costly, highlighting the urgent need for more efficient alternatives. This study introduces a novel approach using mixed matrix membranes (MMMs) infused with Zeolitic Imidazolate Framework-8 (ZIF-8) transformed into its porous liquid (PL) form, aimed at enhancing the separation efficiency of butanol/water mixtures through pervaporation (PV). We selected ZIF-8 for its hydrophobic nature and high surface area, which are critical for improving both flux and selectivity in membrane-based separation processes. The study details the synthesis of ZIF-8-PL, its characterization through techniques such as Fourier Transform Infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM), and the fabrication of the MMMs. Our results demonstrate that ZIF-8-PL-based membranes at 55°C with a 30 wt% PL loading significantly enhance biobutanol-selective PV efficiency. Specifically, these membranes show an improvement in flux of approximately 102% and an increase in separation factor by 64% when compared to unmodified polydimethylsiloxane (PDMS) membranes. This significant enhancement highlights the effectiveness of PL-based fillers in advancing MMM performance for biofuel separation, providing a promising route to optimize energy efficiency and cost-effectiveness in industrial scale applications.

An investigation of a process for selective biogas desulfurization and autotrophic denitrification in a membrane supported reactor

A lab-scale dense polydimethylsiloxane (PDMS) membrane bioscrubber (MBS) was used for selective removal of highly toxic H2S from biogas under autotrophic conditions for the first time. The performance of MBS was evaluated under the effects of sulfide loadings, pH, and hydraulic retention time (HRT). The results showed that gradual increase in sulfide loading rate from 131 to 316 g/m3.d boost S/N ratios 1.9–4.0, on average sulfide oxidation efficiencies higher than 95% were achieved. The S/N ratios were determinant on the formation of oxidation products, but not on the H2S gas removal efficiency. The transition of HRT significantly affected the denitrification rather than the sulfide oxidation, when HRT reduced from 24 to 12 h the nitrate removal efficiency suddenly dropped from 98% to 70%. Increasing the pH values from 7.0 to 9.0 also decreased the sulfide oxidation efficiency from 97±0.5–92±1.1%. Denitrification efficiency > 96% was observed between pH value of 7.0 and 8.0, whereas at pH 9.0 dropped rapidly to 82%. In the whole experiment time there was no membrane-induced problem that adversely affected the system performance. Over-all the developed anoxic dense MBS successfully employed for selective removal of 10,000 ppm H2S and nitrate concurrently with low chemical consumption, possibility for recovery of elemental sulfur, enhanced CH4 calorific value and eliminating the risks of explosion and dilution of biogas. The current work showed the PDMS MBS system is a promising alternative way in biological nitrogen removal and biogas desulfurization under anoxic conditions. Its application in real scale would have high economic importance.

Effects of Solvents on the Material Properties of Screen‐Printed Electrodes and a Polydimethylsiloxane Dielectric for Dielectric Elastomer Transducers

Dielectric elastomer transducers (DETs), namely, highly stretchable dielectric membranes sandwiched between two compliant electrodes, allow to develop sensors, actuators, and generator systems. DET performance is strongly influenced by the material properties of dielectric and electrodes, as well as the type of manufacturing process. For instance, when manufacturing the electrodes via screen‐printing, significant amounts of solvents are needed to adjust the printing materials’ viscosity, but they potentially alter DET properties. The investigation of this effect, however, is largely unexplored. Addressing this issue, this article investigates the influence of various solvents on a DET consisting of a polydimethylsiloxane (PDMS) membrane with PDMS/carbon black electrodes. Physical and chemical interactions between dielectric and solvents are characterized by infrared‐spectroscopy (IR), optical investigations, and light microscopy. Different solvents used for screen‐printing are analyzed in terms of their effects on the electrode electrical resistance, screen‐print image, and breakdown strength. Even though the solvent strongly affects the electrodes’ electrical resistance (ranging from ≈22 kΩ to >MΩ), it does not modify the breakdown strength of the pure dielectric (113 V μm−1). In the IR, no chemical aging is found. The obtained results provide systematic guidelines for the choice of solvents in DET electrode manufacturing.

Mitigated CH4 release of anaerobic waste fermentation is enabled through effluent degassing system equipped with a polydimethylsiloxane membrane contactor

In this study, first, a fed-batch biogas fermenter was established using anaerobic digester sludge treating secondary sludge from a municipal wastewater treatment plant and operated for 120 days on glycerol as the sole substrate. Then, the prefiltered effluent of the anaerobic digester unit was loaded subsequently into a stirred-tank coupled with a hollow-fibre, polydimethylsiloxane (PDMS) gas-liquid membrane contactor and a dissolved methane sensor for studying the gas recovery process under continuous biogas supply, consisting of CH4 and CO2 in different proportions (70/30 CH4/CO2 vol.%; 50/50 CH4/CO2 vol.%; 30/70 CH4/CO2 vol.%.). Experiments showed that besides the actual composition of the internal biogas, the ratio (0.5–2) of sweep gas (N2) and effluent (liquid) volumetric flow rates (G/L) could be a crucial operating factor with influence on the degassing efficiency attainable by the 1 m2 PDMS membrane module. Results were compared to the performance of the same PDMS membrane module working with synthetic anaerobic digester effluents, indicating the dissolved methane recoveries observed with the synthetic effluents (>50 %) considerably surpassed those with the real effluent (<20 %) where the dissolved methane concentrations, at G/L of 1, were in the range of 12.4 to 17.3 mg L−1.

Splay aligned liquid crystal network photoactuators for integrated microfluidic pumps

As lab-on-a-chip devices aim to incorporate complex and multi-step microfluidic workflows, active fluid control within these platforms is critical. We use a splay aligned liquid crystal network (LCN) photoactuator, capable of deformation upon blue light illumination, as a stimuli responsive material to create integrated fluidic elements. After optimization of the manufacturing parameters, a well-defined actuator material is attained. Illumination with a 455 nm light emitting diode (LED) at 41 mW cm−2 achieves deflection of a 3 × 8 × 0.05 mm LCN film by 380 µm, generating forces of 1.1 mN. The actuator response is stable over time and scalable by light intensity, temperature, and size of the LCN film. By combining with a polydimethylsiloxane (PDMS) membrane, integration into a microfluidic chip is demonstrated and fluid movement of 77 nL in a 2 s stroke is attained. In a pumping setup, the LCN film functions as pumping membrane and two passive PDMS check valves complete the integrated micropump. Constant pumping rates of 0.1 µL min−1 are achieved. An advantage of this micropump setup lies in the non-contact actuation method, which allows for easy integration into microfluidic chips, without the need for chip-to-world connections. Furthermore, with the simple manufacturing procedure and the low operating power, important requirements for application in point-of-care settings are fulfilled.

Mechanical analysis of PDMS films based on different hyperelastic numerical constitutive models

PDMS(polydimethylsiloxane) is widely employed as a substrate material in flexible electronic devices, necessitating its ability to undergo camber deformation while maintaining excellent ductility and flexibility. Understanding the mechanical behavior of PDMS is imperative for its practical applications. Consequently, to numerically investigate the tensile behavior of PDMS, two commonly used hyperelastic constitutive models, the Mooney-Rivlin model and the 3-term Ogden model, have been employed to describe its mechanical characteristics. The material coefficients were determined by fitting the uniaxial tensile experimental data. Subsequently, separate finite element models were developed for the PDMS membrane and the Cu-PDMS composite layer structure. The numerical findings demonstrate that both the Mooney-Rivlin model and the 3-term Ogden model adequately fit the experimental data. Nevertheless, in comparison to the 3-term Ogden model, the PDMS stress distribution exhibits higher values at the same tensile rate, consequently resulting in the fracture of the Cu layer first.

Hydrophobic enrichment-induced augmentation of NH2-UiO-66 particle interactions for enhanced pervaporation performance of polydimethylsiloxane membrane

BackgroundIn this research, we aimed to improve the hydrophobic property of NH2-UiO-66 particles by palmitoyl chloride (PC) modification. PC-UiO-66 particles were mixed in the selective layer of PDMS (polydimethylsiloxane)-PVDF (Polyvinylidene fluoride) composite membrane for organo-selective pervaporation. MethodsWe effectively preserved conspicuous crystallinity and high porosity during a conversion from hydrophilic to hydrophobic MOF, as confirmed by XRD and BET studies. The successful incorporation of palmitoyl long alkyl chains into PC-UiO-66 was verified through FTIR, XPS, and EDS studies. PC-UiO-66 particles exhibited an excellent dispersion in PDMS matrix due to a strong interfacial polymer-MOF interaction observed in FESEM and AFM studies. An organophilic pervaporation separation performance of pristine PDMS, NH2-UiO-66/PDMS, and PC-UiO-66/PDMS membranes coated on PVDF support was evaluated for ethanol/water, IPA/water, and 1,5 PDO/IPA feed solution. Significant findingsThe results demonstrated that adding PC-UiO-66 particles significantly improved the separation performance of PC-UiO-66/PDMS membranes, achieving the highest selectivity compared to pristine PDMS and NH2-UiO-66/PDMS membranes.

The nature of PDMS affects the results of the immunoassays carried out in microfluidic channels

Due to various physical or biochemical processes, the nature of polydimethylsiloxane (PDMS) could affect the sensitivity and accuracy of immunoassays performed in microfluidic channels. An appropriate PDMS membrane with high adsorption properties and low background noise allows more sensitive detection of biomarkers. Here, we explored the unusual correlation between membrane surface properties and the signal-to-noise ratio (SNR) of immunoassay, developed a microfluidic-based versatile point-of-care (MVP) detection system on PDMS membrane to simultaneously detect multiple vitamins from multiple human serums. Compared with conventional enzyme-linked immunosorbent assay (ELISA) and Roche electroluminescence method, the MVP detection system exhibits a lower consumption of sample and reagents (10 µL per test), a lower limit of detection (LOD: 6.15 ng/mL), a higher SNR (33.49 dB) and multiplexed ability (seven samples and two targets in one assay). Our MVP detection system can quantitatively detect folic acid (FA) and vitamin D3 (VD3) from human serums and shows good consistency with ELISA and Roche electroluminescence methods. The R square values of FA and VD3 detections are 0.94 and 0.91, respectively. The MVP system is more cost-effective than utilizing conventional methods for a single detection (about 0.04 USD for each target) because of the straightforward design of our detection instruments, their superior anti-interference capabilities, and the low cost of routine instrument maintenance.