Live 3D imaging and mapping of shear stresses within tissues using incompressible elastic beads.

To investigate the role of mechanical constraints in morphogenesis and development, we have developed a pipeline of techniques based on incompressible elastic sensors. These techniques combine the advantages of incompressible liquid droplets, which have been used as precise in situ shear stress sensors, and of elastic compressible beads, which are easier to tune and to use. Droplets of a polydimethylsiloxane mix, made fluorescent through specific covalent binding to a rhodamin dye, are produced by a microfluidics device. The elastomer rigidity after polymerization is adjusted to the tissue rigidity. Its mechanical properties are carefully calibrated in situ, for a sensor embedded in a cell aggregate submitted to uniaxial compression. The local shear stress tensor is retrieved from the sensor shape, accurately reconstructed through an active contour method. In vitro, within cell aggregates, and in vivo, in the prechordal plate of the zebrafish embryo during gastrulation, our pipeline of techniques demonstrates its efficiency to directly measure the three dimensional shear stress repartition within a tissue.

Energy and spectroscopic parameters of neutral and cations isomers of the CnH2 (n = 2-6) families using high-level ab-initio approaches.

Cationic species, previously detected from ion-induced desorption of solid methane by plasma desorption mass spectrometry (PDMS), and neutral species, are investigated using high-level ab-initio approaches. From a set of 25 cationic and 26 neutral structures belonging to CnH2 (n = 2-6) families, it was obtained the energy, rotational constants, harmonic vibrational frequency, charge distribution and excitation energies. The ZPVE-corrected energies, at CCSD(T)-F12; CCSD(T)-F12/RI/(cc-pVTZ-F12, cc-pVTZ-F12-CABS, cc-pVQZ/C) (n = 2-5) and CCSD(T)/cc-pVTZ (n = 6) levels, reveal that the topology of the most stable isomer vary with n and the charge. Out of 674 harmonic frequencies, those with maximum intensity are generally in the 3000-3500 cm-1 range. Analysis of 169 vertical transition energies calculated with the EOM-CCSD approach, suggest three C6H2 species as potential carriers of the diffuse interstellar bands (DIB). Systematic comparison of properties between neutral and cationic species can assist in the structural description of complex matrices.

Anisotropic Superhydrophobic Properties Replicated from Leek Leaves.

A bio-inspired approach to fabricate robust superhydrophobic (SHB) surfaces with anisotropic properties replicated from a leek leaf is presented. The polydimethylsiloxane (PDMS) replica surfaces exhibit anisotropic wetting, anti-icing, and light scattering properties due to microgrooves replicated from leek leaves. Superhydrophobicity is achieved by a novel modified candle soot (CS) coating that mimics leek's epicuticular wax. The resulting surfaces show a contact angle (CA) difference of ≈30° in the directions perpendicular and parallel to the grooves, which is similar to the anisotropic properties of the original leek leaf. The coated replica is durable, withstanding cyclic bending tests (up to 10 000 cycles) and mechanical sand abrasion (up to 60 g of sand). The coated replica shows low ice adhesion (10 kPa) after the first cycle; and then, increases to ≈70 kPa after ten icing-shearing cycles; while, anisotropy in ice adhesion becomes more evident with more cycles. In addition, the candle soot-coated positive replica (CS-coated PR) demonstrates a transmittance of ≈73% and a haze of ≈65% at the wavelength of 550 nm. The results show that the properties depend on the replicated surface features of the leek leaf, which means that the leek leaf appears to be a highly useful template for bioinspired surfaces.

Arrays of Bowl-Shaped Janus Particle Film with Structured Colors.

Structural colors generated via total internal reflection (TIR) using nanostructure-free micro-concave shapes have garnered increasing attention. However, the application of large micro-concave structures for structural coloration remains limited. Herein, a flexibly tunable structural color film fabricated by casting polydimethylsiloxane (PDMS) on an array of large poly(glycidyl methacrylate) (PGMA) bowl-shaped particles is reported. The resultant film exhibits tunable red to green structural colors with changing observation angles. Moreover, the color can be further tailored by altering the shape of the film itself. The incorporation of the PDMS layer not only facilitates a shift in the locus of TIR from the bottom surface to the top concave surface of the particles, thereby enabling the generation of structural color, but also confers enhanced flexibility to the film. Further decoration with silver nanoparticles imparts antimicrobial properties, yielding a novel antimicrobial coating material with structural colors. The simple and cost-effective strategy for the production of structural color films provides potential applications in antimicrobial coatings, enabling accessible and customizable structural coloration using big-size micro-concave particles.

Circulating Tumor Cell Phenotype Detection and Epithelial-Mesenchymal Transition Tracking Based on Dual Biomarker Co-Recognition in an Integrated PDMS Chip.

Circulating tumor cells (CTCs) are widely considered as a reliable and promising class of markers in the field of liquid biopsy. As CTCs undergo epithelial-mesenchymal transition (EMT), phenotype detection of heterogeneous CTCs based on EMT markers is of great significance. In this report, an integrated analytical strategy that can simultaneously capture and differentially detect epithelial- and mesenchymal-expressed CTCs in bloods of non-small cell lung cancer (NSCLS) patients is proposed. First, a commercial biomimetic polycarbonate (PCTE) microfiltration membrane is employed as the capture interface for heterogenous CTCs. Meanwhile, differential detection of the captured CTCs is realized by preparing two distinct CdTe quantum dots (QDs) with red and green emissions, attached with EpCAM and Vimentin aptamers, respectively. For combined analysis, a polydimethylsiloxane (PDMS) chip with simple structure is designed, which integrates the membrane capture and QDs-based phenotype detection of CTCs. This chip not only implements the analysis of the number of CTCs down to 2 cells mL-1, but enables EMT process tracking according to the specific signals of the two QDs. Finally, this method is successfully applied to inspect the correlations of numbers or proportions of heterogenous CTCs in 94 NSCLS patients with disease stage and whether there is distant metastasis.

Substrate elasticity does not impact DNA methylation changes during differentiation of pluripotent stem cells.

BACKGROUND AIMS: Substrate elasticity may direct cell-fate decisions of stem cells. However, it is largely unclear how matrix stiffness affects the differentiation of induced pluripotent stem cells (iPSCs) and whether this is also reflected by epigenetic modifications. METHODS: We cultured iPSCs on tissue culture plastic (TCP) and polydimethylsiloxane (PDMS) with different Young's modulus (0.2 kPa, 16 kPa or 64 kPa) to investigate the sequel on growth and differentiation toward endoderm, mesoderm and ectoderm. RESULTS: Immunofluorescence and gene expression of canonical differentiation markers were hardly affected by the substrates. Notably, when we analyzed DNA methylation profiles of undifferentiated iPSCs or after three-lineage differentiation, we did not see any significant differences on the three different PDMS elasticities. Only when we compared DNA methylation profiles on PDMS-substrates versus TCP we did observe epigenetic differences, particularly on mesodermal differentiation. CONCLUSIONS: Stiffness of PDMS substrates did not affect directed differentiation of iPSCs, whereas the moderate epigenetic differences on TCP might also be attributed to other chemical parameters.

Enhanced adhesive and mechanically robust silicone-based coating with excellent marine anti-fouling and anti-corrosion performances.

Poly(dimethylsiloxane) (PDMS) is widely used in marine antifouling coatings due to its low surface energy property. However, certain drawbacks of PDMS coatings such as poor surface adhesion, weak mechanical properties, and inadequate static antifouling performance have hindered its practical applications. Herein, condensation polymerization is utilized to prepare PDMS-based polythiamine ester (PTUBAF) coatings that consist of PDMS, polytetrahydrofuran (PTMG), 2, 3, 5, 6-tetrafluoro-1, 4-benzenedimethanol (TBD) as the main chains and isobornyl acrylate(IBA) as the antifouling group. The surface adhesion to the substrate is enhanced due to the hydrogen bond between the coated carbamate group and the hydroxyl group on the surface of the substrate. Mechanical properties of PTUBAF are significantly improved due to the benzene ring and six-membered ring biphase hard structure. The strong synergistic effect of bactericidal groups and low surface energy surface endows the PTUBAF coating with outstanding antifouling performance. Due to the low surface energy surface, the PTUBAF coatings are also found to possess excellent anti-corrosion. Furthermore, since the PTUBAF coatings exhibit a visible light transmittance of 91 %, they can applied as protective films for smartphones. The proposed method has the potential to boost the production and practical applications of silicone-based coatings.

Integrating Benzoxazine-PDMS 3D Networks with Carbon Nanotubes for flexible Pressure Sensors.

Shapeable and flexible pressure sensors with superior mechanical and electrical properties are of major interest as they can be employed in a wide range of applications. In this regard, elastomer-based composites incorporating carbon nanomaterials in the insulating matrix embody an appealing solution for designing flexible pressure sensors with specific properties. In this study, PDMS chains of different molecular weight were successfully functionalized with benzoxazine moieties in order to thermally cure them without adding a second component, nor a catalyst or an initiator. These precursors were then blended with 1 weight percent of multi-walled carbon nanotubes (CNTs) using an ultrasound probe, which induced a transition from a liquid-like to a gel-like behavior as CNTs generate an interconnected network within the matrix. After curing, the resulting nanocomposites exhibit mechanical and electrical properties making them highly promising materials for pressure-sensing applications.

A highly efficient cell culture method using oxygen-permeable PDMS-based honeycomb microwells produces functional liver organoids from human induced pluripotent stem cell-derived carboxypeptidase M liver progenitor cells.

Recent advancements in bioengineering have introduced potential alternatives to liver transplantation via the development of self-assembled liver organoids, derived from human-induced pluripotent stem cells (hiPSCs). However, the limited maturity of the tissue makes it challenging to implement this technology on a large scale in clinical settings. In this study, we developed a highly efficient method for generating functional liver organoids from hiPSC-derived carboxypeptidase M liver progenitor cells (CPM+ LPCs), using a microwell structure, and enhanced maturation through direct oxygenation in oxygen-permeable culture plates. We compared the morphology, gene expression profile, and function of the liver organoid with those of cells cultured under conventional conditions using either monolayer or spheroid culture systems. Our results revealed that liver organoids generated using polydimethylsiloxane-based honeycomb microwells significantly exhibited enhanced albumin secretion, hepatic marker expression, and cytochrome P450-mediated metabolism. Additionally, the oxygenated organoids consisted of both hepatocytes and cholangiocytes, which showed increased expression of bile transporter-related genes as well as enhanced bile transport function. Oxygen-permeable polydimethylsiloxane membranes may offer an efficient approach to generating highly mature liver organoids consisting of diverse cell populations.

Fabrication of SU-8 polymer micro/nanoscale nozzle by hot embossing method.

Electrohydrodynamic-jet printing (E-jet printing) is a direct-writing technology for manufacturing micro-nano devices. To further reduce the inner diameter of the nozzle to improve the printing resolution, a large-scale manufacturing method of SU-8 polymer micro/nanoscale nozzle by means of a process combining UV exposure and hot embossing was proposed. To improve the adhesive strength between the UV mask and SU-8, the influence of the oxygen plasma treatment parameters on the water contact angles of the UV mask was analyzed. The effect of hot embossing time and temperature on the replication precision was studied. The influence of UV exposure parameters and thermal bonding parameters on the micro and nanochannel pattern was investigated. The SU-8 polymer nozzles with 188 ± 3 nm wide and 104 ± 2 nm deep nanochannels were successfully fabricated, and the replication precision can reach to 98.5%. The proposed manufacturing method of SU-8 polymer nozzles in this study will significantly advance the research on the transport properties of nanoscale channels in E-jet nozzles and facilitate further advancements in E-jet based applications.

Microscale Chaotic Mixing as a Driver for Chemical Reactions in Porous Media.

Mixing-induced reactions play a key role in a large range of biogeochemical and contaminant transport processes in the subsurface. Fluid flow through porous media was recently shown to exhibit chaotic mixing dynamics at the pore scale, enhancing microscale concentration gradients and controlling mixing rates. While this phenomenon is likely ubiquitous in environmental systems, it is not known how it affects chemical reactions. Here, we use refractive index matching and laser-induced fluorescence imaging of a bimolecular redox reaction to investigate the consequence of pore scale chaotic mixing on the reaction rates. The overestimation of measured reaction rates by the classical macrodispersion model highlights the persistence of incomplete mixing on the pore scale. We show that the reaction product formation is controlled by microscale chaotic mixing, which induces an exponential increase of the mixing interface and of the reaction rates. We derive a reactive transport model that captures experimental results and predicts that chaotic mixing has a first order control on reaction rates across a large range of time scales and Péclet and Damköhler numbers. These findings provide a new framework for understanding, assessing, and predicting mixing-induced reactions and their role on the fate and mobility of environmental compounds in natural porous media.

Spectral Characteristics of Water-Soluble Rhodamine Derivatives for Laser-Induced Fluorescence.

We present a comprehensive fluorescence characterization of seven water-soluble rhodamine derivatives for applications in laser-induced fluorescence (LIF) techniques. Absorption and emission spectra for these dyes are presented over the visible spectrum of wavelengths (400 to 700 nm). Their fluorescence properties were also investigated as a function of temperature for LIF thermometry applications. Rhodamine 110 depicted the least fluorescence emission sensitivity to temperature at -0.11%/°C, while rhodamine B depicted the most with a -1.55%/°C. We found that the absorption spectra of these molecules are independent of temperature, supporting the notion that the temperature sensitivity of their emission only comes from changes in quantum yield with temperature. Conversely, these rhodamine fluorophores showed no change in emission intensities with pH variations and are, therefore, not suitable tracers for pH measurements. Similarly, fluorescent lifetime, which is also a property sensitive to local environmental changes in temperature, pH, and ion concentration, measurements were conducted for these fluorophores. It was found that rhodamine B and kiton red 620 have shorter fluorescence timescales compared to those of the other five rhodamine dyes, making them least suitable for applications where temporal changes in emission are monitored. Lastly, we conducted experiments to assess the physicochemical absorption characteristics of these dyes' molecules into polydimethylsiloxane (PDMS), the most common material for microfluidic devices. Rhodamine B showed the highest diffusion into PDMS substrates as compared to the other derivative dyes.

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 1486 g 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.

Solvent Extraction of PDMS Tubing as a New Method for the Capture of Volatile Organic Compounds from Headspace.

Polydimethylsiloxane (PDMS) tubing is increasingly being used to collect volatile organic compounds (VOCs) from static biological headspace. However, analysis of VOCs collected using PDMS tubing often deploys thermal desorption, where samples are considered as 'one-offs' and cannot be used in multiple experiments. In this study, we developed a static headspace VOC collection method using PDMS tubing which is solvent-based, meaning that VOC extracts can be used multiple times and can be linked to biological activity. Using a synthetic blend containing a range of known semiochemicals (allyl isothiocyanate, (Z)-3-hexen-1-ol, 1-octen-3-one, nonanal, (E)-anethol, (S)-bornyl acetate, (E)-caryophyllene and pentadecane) with differing chemical and physicochemical properties, VOCs were collected in static headspace by exposure to PDMS tubing with differing doses, sampling times and lengths. In a second experiment, VOCs from oranges were collected using PDMS sampling of static headspace versus dynamic headspace collection. VOCs were eluted with diethyl ether and analysed using gas chromatography - flame ionization detector (GC-FID) and coupled GC - mass spectrometry. GC-FID analysis of collected samples showed that longer PDMS tubes captured significantly greater quantities of compounds than shorter tubes, and that sampling duration significantly altered the recovery of all tested compounds. Moreover, greater quantities of compounds were recovered from closed compared to open systems. Finally, analysis of orange headspace VOCs showed no qualitative differences in VOCs recovered compared to dynamic headspace collections, although quantities sampled using PDMS tubing were lower. In summary, extraction of PDMS tubing with diethyl ether solvent captures VOCs from the headspace of synthetic blends and biological samples, and the resulting extracts can be used for multiple experiments linking VOC content to biological activity.

A glaucoma micro-stent with diverging channel and stepped shaft structure based on microfluidic template processing technology.

BACKGROUND: Minimally invasive glaucoma surgery (MIGS) has experienced a surge in popularity in recent years. Glaucoma micro-stents serve as the foundation for these minimally invasive procedures. Nevertheless, the utilization of these stents still presents certain short-term and long-term complications. This study aims to elucidate the creation of a novel drainage stent implant featuring a diverging channel, produced through microfluidic template processing technology. Additionally, an analysis of the mechanical properties, biocompatibility, and feasibility of implantation is conducted. RESULTS: The stress concentration value of the proposed stent is significantly lower, approximately two to three times smaller, compared to the currently available commercial XEN gel stent. This indicates a stronger resistance to bending in theory. Theoretical calculations further reveal that the initial drainage efficiency of the gradient diverging drainage stent is approximately 5.76 times higher than that of XEN stents. Notably, in vivo experiments conducted at the third month demonstrate a favorable biocompatibility profile without any observed cytotoxicity. Additionally, the drainage stent exhibits excellent material stability in an in vitro simulation environment. CONCLUSIONS: In summary, the diverging drainage stent presents a novel approach to the cost-effective and efficient preparation process of minimally invasive glaucoma surgery (MIGS) devices, offering additional filtering treatment options for glaucoma.

Investigating the anti-bioadhesion properties of short, medium chain length, and amphiphilic polyhydroxyalkanoate films.

Silicone materials are widely used in fouling release coatings, but developing eco-friendly protection via biosourced coatings, such as polyhydroxyalcanoates (PHA) presents a major challenge. Anti-bioadhesion properties of medium chain length PHA and short chain length PHA films are studied and compared with a reference Polydimethylsiloxane coating. The results highlight the best capability of the soft and low-roughness PHA-mcl films to resist bacteria or diatoms adsorption as compared to neat PDMS and PHBHV coatings. These parameters are insufficient to explain all the results and other properties related to PHA crystallinity are discussed. Moreover, the addition of a low amount of PEG copolymers within the coatings, to create amphiphilic coatings, boosts their anti-adhesive properties. This work reveals the importance of the physical or chemical ambiguity of surfaces in their anti-adhesive effectiveness and highlights the potential of PHA-mcl film to resist the primary adhesion of microorganisms.

Improvements in in vitro spermatogenesis: oxygen concentration, antioxidants, tissue-form design, and space control.

Incorporation of bovine serum-derived albumin formulation (AlbuMAX) into a basic culture medium, MEMα, enables the completion of in vitro spermatogenesis through testicular tissue culture in mice. However, this medium was not effective in other animals. Therefore, we sought an alternative approach for in vitro spermatogenesis using a synthetic medium without AlbuMAX and aimed to identify its essential components. In addition to factors known to be important for spermatogenesis, such as retinoic acid and reproductive hormones, we found that antioxidants (vitamin E, vitamin C, and glutathione) and lysophospholipids are vital for in vitro spermatogenesis. Moreover, based on our experience with microfluidic devices (MFD), we developed an alternative approach, the PDMS-ceiling method (PC method), which involves simply covering the tissue with a flat chip made of PDMS, a silicone resin material used in MFD. The PC method, while straightforward, integrates the advantages of MFD, enabling improved and uniform oxygen and nutrient supply via tissue flattening. Furthermore, our studies underscored the significance of lowering the oxygen concentration to 10-15%. Using an integrated cultivation method based on these findings, we successfully achieved in vitro spermatogenesis in rats, which has been a long-standing challenge. Further improvements in culture conditions would pave the way for spermatogenesis completion in diverse animal species.

Efficient enrichment of free target sequences in an integrated microfluidic device for point-of-care detection systems.

Nucleic acid biomarker detection has great importance in the diagnosis of disease, the monitoring of disease progression and the classification of patients according to treatment decision making. Nucleic acid biomarkers found in the blood of patients have generated a lot of interest due to the possibility of being detected non-invasively which makes them ideal for monitoring and screening tests and particularly amenable to point-of-care (POC) or self-testing. A major challenge to POC molecular diagnostics is the need to enrich the target to optimise detection. In this work, we describe a microfabricated device for the enrichment of short dsDNA target sequences, which is especially valuable for potential detection methods, as it improves the probability of effectively detecting the target in downstream analyses. The device integrated a heating element and a temperature sensor with a microfluidic chamber to carry out the denaturation of the dsDNA combined with blocking-probes to enrich the target. This procedure was validated by fluorescence resonance energy transfer (FRET) technique, labelling DNA with a fluorophore and a quencher. As proof of concept, a 23-mer long dsDNA sequence corresponding to the L858R mutation of the EGFR gene was used. The qualitative results obtained determined that the most optimal blocking rate was obtained with the incorporation of 11/12-mer blocking-probes at a total concentration of 6 µM. This device is a powerful DNA preparation tool, which is an indispensable initial step for subsequent detection of sequences via nucleic acid hybridisation methods.

Pre-enrichment-free detection of hepatocellular carcinoma-specific ctDNA via PDMS and MEMS-based microfluidic sensor.

The growing interest in microfluidic biosensors has led to improvements in the analytical performance of various sensing mechanisms. Although various sensors can be integrated with microfluidics, electrochemical ones have been most commonly employed due to their ease of miniaturization, integration ability, and low cost, making them an established point-of-care diagnostic method. This concept can be easily adapted to the detection of biomarkers specific to certain cancer types. Pathological profiling of hepatocellular carcinoma (HCC) is heterogeneous and rather complex, and biopsy samples contain limited information regarding the tumor and do not reflect its heterogeneity. Circulating tumor DNAs (ctDNAs), which can contain information regarding cancer characteristics, have been studied tremendously since liquid biopsy emerged as a new diagnostic method. Recent improvements in the accuracy and sensitivity of ctDNA determination also paved the way for genotyping of somatic genomic alterations. In this study, three-electrode (Au-Pt-Ag) glass chips were fabricated and combined with polydimethylsiloxane (PDMS) microchannels to establish an electrochemical microfluidic sensor for detecting c.747G > T hotspot mutations in the TP53 gene of ctDNAs from HCC. The preparation and analysis times of the constructed sensor were as short as 2 h in total, and a relatively high flow rate of 30 µl/min was used during immobilization and hybridization steps. To the best of our knowledge, this is the first time a PDMS-based microfluidic electrochemical sensor has been developed to target HCC ctDNAs. The system exhibited a limit of detection (LOD) of 24.1 fM within the tested range of 2-200 fM. The sensor demonstrated high specificity in tests conducted with fully noncomplementary and one-base mismatched target sequences. The developed platform is promising for detecting HCC-specific ctDNA at very low concentrations without requiring pre-enrichment steps.

Highly Sensitive Pressure Sensor Based on Elastic Conductive Microspheres.

Elastic pressure sensors play a crucial role in the digital economy, such as in health care systems and human-machine interfacing. However, the low sensitivity of these sensors restricts their further development and wider application prospects. This issue can be resolved by introducing microstructures in flexible pressure-sensitive materials as a common method to improve their sensitivity. However, complex processes limit such strategies. Herein, a cost-effective and simple process was developed for manufacturing surface microstructures of flexible pressure-sensitive films. The strategy involved the combination of MXene-single-walled carbon nanotubes (SWCNT) with mass-produced Polydimethylsiloxane (PDMS) microspheres to form advanced microstructures. Next, the conductive silica gel films with pitted microstructures were obtained through a 3D-printed mold as flexible electrodes, and assembled into flexible resistive pressure sensors. The sensor exhibited a sensitivity reaching 2.6 kPa-1 with a short response time of 56 ms and a detection limit of 5.1 Pa. The sensor also displayed good cyclic stability and time stability, offering promising features for human health monitoring applications.