Optimizing Droplet-Based Electricity Generator via a Low Sticky Hydrophobic Droplet-Impacted Surface

Droplet-based electricity generators (DEGs) are increasingly recognized for their potential in converting renewable energy sources. This study explores the interplay of surface hydrophobicity and stickiness in improving DEG efficiency. It find that the high-performance C-WaxDEGs leverage both these properties. Specifically, DEGs incorporating polydimethylsiloxane (PDMS) with carnauba wax (C-wax) exhibit increased output as surface stickiness decreases. Through experimental comparisons, PDMS with 1wt.% C-wax demonstrated a significant power output increase from 0.07 to 1.2 W m- 2, which attribute to the minimized adhesion between water molecules and the polymer surface, achieved by embedding C-wax into PDMS surface to form microstructures. This improvement in DEG performance is notable even among samples with similar surface potentials and contact angles, suggesting that C-wax's primary contribution is in reducing surface stickiness rather than altering other surface properties. The further investigations into the C-WaxDEG variant with 1wt.% C-wax PDMS uncover its potential as a sensor for water quality parameters such as temperature, pH, and heavy metal ion concentration. These findings open avenues for the integration of C-WaxDEGs into flexible electronic devices aimed at environmental monitoring.

Surface electromyography using dry polymeric electrodes

Conventional wet Ag/AgCl electrodes are widely used in electrocardiography, electromyography (EMG), and electroencephalography (EEG) and are considered the gold standard for biopotential measurements. However, these electrodes require substantial skin preparation, are single use, and cannot be used for continuous monitoring (>24 h). For these reasons, dry electrodes are preferable during surface electromyography (sEMG) due to their convenience, durability, and longevity. Dry conductive elastomers (CEs) combine conductivity, flexibility, and stretchability. In this study, CEs combining poly(3,4-ehtylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) in polyurethane are explored as dry, skin contacting EMG electrodes. This study compares these CE electrodes to commercial wet Ag/AgCl electrodes in five subjects, classifying four movements: open hand, fist, wrist extension, and wrist flexion. Classification accuracy is tested using a backpropagation artificial neural network. The control Ag/AgCl electrodes have a 98.7% classification accuracy, while the dry conductive elastomer electrodes have a classification accuracy of 99.5%. As a conclusion, PEDOT based dry CEs were shown to successfully function as on-skin electrodes for EMG recording, matching the performance of Ag/AgCl electrodes, while addressing the need for minimal skin prep, no gel, and wearable technology.

Synthesis and characterization of low surface energy thermoplastic polyurethane elastomers based on polydimethylsiloxane

Organosilicon modified polyurethane elastomers (Si-MTPUs) were synthesized in order to improve the anti-graffiti property of thermoplastic polyurethane elastomers (TPUs). Si-MTPUs were prepared from polydimethylsiloxane (PDMS) and polytetramethylene glycol (PTMG) as mixed soft segment, 1,4-butanediol (BDO) and imidazole salt ionic liquid N-glyceryl-N-methyl imidazolium chloride ([MIM_l,g]Cl) used as chain extender, and 4,4'-dicyclohexylmethane diisocyanate (HMDI). The structure, thermal stability, mechanical properties and physical crosslinking density of Si-MTPUs were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetry analysis (TGA), mechanical test and low field nuclear magnetic resonance. Surface energy and water absorption were characterized by static contact angle test and water resistance test, and anti-graffiti and self-cleaning properties were characterized with water, milk, ink, lipstick, oily markers and spray paint. It was found that the mechanical properties of Si-MTPU-10 with the content of PDMS 10 wt% were optimized, with a maximum tensile strength of 32.3 MPa and elongation at break of 656%. Surface energy reached the minimum value of 23.1 mN m^-1 with the best anti-graffiti performance, which no longer decreased with the increase of PDMS contents. This work provides novel idea and strategy for the preparation of low surface energy TPUs.

Fabrication and design of poly(l-lactic acid) membrane for passive MAP packaging of Brassica chinensis L

PLD_x L copolymers were synthesized from physically stable rigid poly(l-lactic acid) (PLLA) and a few different molecular weights of polydimethylsiloxane (PDMS) to increase the O₂ and CO₂ permeabilities of PLLA films and make them acceptable for packaging highly respirable products. The effect of PDMS on the morphology, mechanical properties, and gas permeability of PLD_x L was investigated. Copolymers showed approximately 10 times the fracture strain and 1.7 times the CO₂ and O₂ permeabilities of neat PLLA. Additionally, PLD_x L maintained an increased CO₂ /O₂ perm-selectivity consistent between 5 and 40°C. Passive modified atmosphere packaging of Brassica chinensis L was developed to assess the membrane's impact on headspace gas inside the package. The results showed that poly(amide)/poly(ethylene) packaging with 48 cm² PLD_1.8 L membrane as a breathing window can provide 50 g B. chinensis L. with a healthy atmosphere of 3%-8% O₂ and 5%-8% CO₂ between 6 and 22 days. Vegetables packaged in PLD_1.8 L had the lower respiration rate, lower nitrite contents, and less proliferation of microorganisms. Moreover, a suitable atmosphere kept vegetables with higher ascorbic acid and a good appearance after more than 2 weeks of storage at 5°C. PRACTICAL APPLICATION: The permeability of the PLLA-based membrane can be adjusted for the breathable window membrane of sealed fresh products. In the future, several types of film could be developed to match the respiratory and metabolic characteristics of different kinds of products. Such PLLA-based specialized membranes can refine the fresh-keeping function and be more attractive to the customer.

Synthesis and characterization of hydroxyl-terminated polybutadiene modified low temperature adaptive self-matting waterborne polyurethane

Hydroxyl-terminated polybutadiene (HTPB) is a flexible telechelic compound with a main chain containing a slightly cross-linked activated carbon-carbon double bond and a hydroxyl group at the end. Therefore, in this paper, HTPB was used as a terminal diol prepolymer, and sulfonate AAS and carboxylic acid DMPA were used as hydrophilic chain extenders to prepare low-temperature adaptive self-matting waterborne polyurethane (WPU). Due to the fact that the non-polar butene chain in the HTPB prepolymer cannot form a hydrogen bond with the urethane group, and the solubility parameter difference between the hard segment formed by the urethane group is large, the gap of T _g between the soft and hard segments of the WPU increases by nearly 10 °C, with more obvious microphase separation. At the same time, by adjusting the HTPB content, WPU emulsions with different particle sizes can be obtained, thereby obtaining WPU emulsions with good extinction properties and mechanical properties. The results show that HTPB-based WPU with a certain degree of microphase separation and roughness obtained by introducing a large number of non-polar carbon chains has good extinction ability, and the 60° glossiness can be as low as 0.4 GU. Meanwhile, the introduction of HTPB can improve the mechanical properties and low temperature flexibility of WPU. The T _g,s (the glass transition temperature of soft segment) of WPU modified by the HTPB block decreased by 5.82 °C, and the ΔT _g increased by 21.04 °C, indicating that the degree of microphase separation increased. At -50 °C, the elongation at break and tensile strength of WPU modified by HTPB can still maintain 785.2% and 76.7 MPa, which are 1.82 times and 2.91 times those of WPU with only PTMG as soft segment, respectively. The self-matting WPU coating prepared in this paper can meet the requirements of severe cold weather and has potential application prospects in the field of finishing.

Radiation curable polysiloxane: synthesis to applications

Among the different types of specialty polymers, polysiloxane finds its position in the pyramid's apex in terms of its performance attributes. Its unique structural features result in it having superior performance benefits over wide operational conditions. Hence, polysiloxanes are used in various industries. Like other polymers, to effectively use polysiloxanes, curing is a non-negotiable fact. Therefore, polysiloxanes are cured using different chemistries such as addition, condensation, and peroxy-mediated methods, etc. However, recently, it has been noted that there is a strong impetus towards developing radiation-curable polysiloxanes. A faster turnover time, higher yield, and marginal involvement in the release of any toxic by-products has resulted in the widespread acceptance of radiation curing techniques. This review article provides insight into the various facets of polysiloxane chemistry, the synthesis of radiation curable polysiloxane, and the curing methodology of polysiloxane using radiation sources such as ultraviolet, electron beam, and gamma radiation. We further provide an account of the various applications of such radiation-curable polysiloxanes.

Semi-interpenetrating polymer networks prepared from castor oil-based waterborne polyurethanes and carboxymethyl chitosan

A series of vegetable oil-based waterborne polyurethane composites were prepared through construction of novel semi-interpenetrating polymers network using carboxymethyl chitosan (CA) as the secondary polymer phase. The effects of CA contents on storage stability, and particle size distribution of the composite dispersions and thermal stability, mechanical properties and surface wettability of composite films were investigated and discussed. The results showed that the composite dispersions displayed excellent storage stability and the biomass contents of resulting films were high up to 80 %. A significant increase in crosslinking density and glass transition temperature of the composite films were observed as the CA contents increased, which was attributed to the increasing hard segment of films and strong hydrogen bonding interaction between polyurethanes and CA. This work provided a simple method to tailor the performance of environmentally friendly vegetable oil-based waterborne polyurethane, which could find application in the field of coatings, adhesives, ink and so on.

A biostable, anti-fouling zwitterionic polyurethane-urea based on PDMS for use in blood-contacting medical devices

Polydimethylsiloxane (PDMS) is commonly used in medical devices because it is non-toxic and stable against oxidative stress. Relatively high blood platelet adhesion and the need for chemical crosslinking through curing, however, limit its utility. In this research, a biostable PDMS-based polyurethane-urea bearing zwitterion sulfobetaine (PDMS-SB-UU) was synthesized for potential use in the fabrication or coating of blood-contacting devices, such as a conduits, artificial lungs, and microfluidic devices. The chemical structure and physical properties of synthesized PDMS-SB-UU were confirmed by 1H-nuclear magnetic resonance (1H-NMR), X-ray diffraction (XRD), and uniaxial stress-strain curve. In vitro stability of PDMS-SB-UU was confirmed against lipase and 30% H2O2 for 8 weeks, and PDMS-SB-UU demonstrated significantly higher resistance to fibrinogen adsorption and platelet deposition compared to control PDMS. Moreover, PDMS-SB-UU showed a lack of hemolysis and cytotoxicity with whole ovine blood and rat vascular smooth muscle cells (rSMCs), respectively. The PDMS-SB-UU was successfully processed into small-diameter (0.80 ± 0.05 mm) conduits by electrospinning and coated onto PDMS- and polypropylene-based blood-contacting biomaterials due to its unique physicochemical characteristics from its soft- and hard- segments.

Compositions Based on PAN Solutions Containing Polydimethylsiloxane Additives: Morphology, Rheology, and Fiber Spinning

The effect of additives of polydimethylsiloxanes (PDMS) with various molecular weights on the morphology and rheological behavior of polyacrylonitrile (PAN) solutions in dimethyl sulfoxide has been analyzed. It was shown that only partial compatibility of the PDMS with the lowest molecular weight member of the homologous series studied—hexamethyldisiloxane—with PAN solution takes place. All other PDMS samples form emulsions with PAN solutions. The coalescence rate of PDMS drops depends on the viscosity ratio of the disperse phase and the continuous medium, which determines both the duration of dispersion preparation and the conditions for processing emulsions into fibers and films. An anomalous change in viscosity for a series of emulsions with different concentrations of additives, associated with the slippage, was detected. The relaxation properties of emulsions “feel” macro-phase separation. Modeling of the wet spinning process has shown that the morphology of the deposited solution drop reflects the movement of the diffusion front, leading to the gathering droplets in the center of the deposited formulation drop or to their localization in a certain arrangement. It was shown that the emulsion jets upon stretching undergo phase separation.

Mechanically robust and tough waterborne polyurethane films based on diselenide bonds and dual H-bonding interactions with fast visible-light-triggered room-temperature self-healability

A dynamic but mechanically robust and tough polymer network was proposed, in which the fast room-temperature self-healing of our target polymer with mechanically robust and tough features is achieved under visible light.

Facile preparation of degradable multi-arm-star-branched waterborne polyurethane with bio-based tannic acid

In this research, biodegradable multi-arm-star-branched waterborne polyurethanes (MWPUs) were prepared by incorporation of bio-based material (tannic acid, TA) in the structure of waterborne polyurethanes. The prepared MWPUs were characterized by UV-vis spectrometry and FT-IR spectrometry, confirming the presence of TA in MWPUs. The results of DSC and TGA demonstrated that the incorporation of TA remarkably enhanced the thermal stability of MWPUs. The mechanical strength test indicated that the Young's modulus and tensile strength of the waterborne polyurethanes after incorporation of TA were significantly improved due to the increase of structural rigidity, hydrogen bonding and the molecular interactions of the TA-based MWPU chains. In addition, the synthesized TA-based MWPUs also exhibited excellent antioxidation capacity and outstanding biodegradation property. Given these excellent properties and the sustainability of TA, the developed TA-based MWPUs exhibited great potential in a wide range of practical applications.

A facile method was developed for preparation of degradable multi-arm-star-branched waterborne polyurethanes (MWPUs) by incorporation of bio-based material (tannic acid, TA) in the structure of waterborne polyurethanes.