Polymeric Devices Research Articles

Measuring Size and Zeta Potential of Nanoparticles with a Salt Gradient

Nanometer-sized lipid vesicles play an important role in the fields of drug delivery and diagnostics. Their size and zeta potential affect their adsorption on the cell membrane and subsequent absorption by the cell. Hence the size and zeta potential are key parameters for designing liposome-based drug delivery vehicles and for understanding the body's cell-to-cell communication with exosomes. Current nanoparticle characterization techniques require, however, several separate experiments and are challenged by heterogeneous samples. Here, we concentrate both exosomes and liposomes from dilute solutions and measure their size and zeta potential in a one-step measurement with a salt gradient in a funnel-shaped nanochannel. The salt gradient induces a diffusiophoretic particle migration towards higher salt concentration and an oppositely directed difussioosmotic fluid flow. Particles in the nanochannel are trapped where the diffusiophoretic particle velocity and the diffusioosmotic fluid velocity balance each other. As the diffusiophoretic particle velocity depends on the particles’ diameter and zeta potential, these parameters can be inferred from a single measurement of the spatial distribution of particles in the trap. We concentrate ensemble of particles to approximately 500 times their initial concentration and characterize them. We also demonstrate trapping and characterization of individual particles, which allows for resolving sample heterogeneity. The trapping position can in both cases be tuned to occur at physiological salinity. The method is implemented in a nanofluidic polymer device that can be mass-produced at low cost, and it is also applicable for other types of nanoparticles. As nanoparticles can be kept in the trap while reactants are introduced in the nanochannel, monitoring surface reaction on nanoparticles can be envisioned.

Differentiation of Electric Response in Highly Oriented Regioregular Poly(3-hexylthiophene) under Anisotropic Strain.

Exploring flexible and stretchable conjugated polymer devices has garnered particular attention. This work provides a new technology to improve the electrical properties in a stretching process by skillfully assisting the anisotropic tensile properties of oriented regioregular poly(3-hexylthiophene) (P3HT) films. Oriented P3HT films with a long-range ordered chain alignment are fabricated, and stretchable conducting films are achieved by laminating oriented P3HT films and polydimethylsiloxane (PDMS) layers. The differentiation of electrical response is identified when the film is under different stretching directions. The electrical stability of the P3HT film during the stretching process is much better when the stretching direction is perpendicular than along the c-axis of the P3HT film. Moreover, the multiscale structure evolution of P3HT films under stretching is explored. The technology based on oriented conductive polymers under anisotropic stretching condition provides not only a new strategy for fabricating high-quality stretchable devices but also theoretical guidance for studying the mechanical properties for the aligned conjugated film.

Recent innovations in cost-effective polymer and paper hybrid microfluidic devices.

Hybrid microfluidic systems that are composed of multiple different types of substrates have been recognized as a versatile and superior platform, which can draw benefits from different substrates while avoiding their limitations. This review article introduces the recent innovations of different types of low-cost hybrid microfluidic devices, particularly focusing on cost-effective polymer- and paper-based hybrid microfluidic devices. In this article, the fabrication of these hybrid microfluidic devices is briefly described and summarized. We then highlight various hybrid microfluidic systems, including polydimethylsiloxane (PDMS)-based, thermoplastic-based, paper/polymer hybrid systems, as well as other emerging hybrid systems (such as thread-based). The special benefits of using these hybrid systems have been summarized accordingly. A broad range of biological and biomedical applications using these hybrid microfluidic devices are discussed in detail, including nucleic acid analysis, protein analysis, cellular analysis, 3D cell culture, organ-on-a-chip, and tissue engineering. The perspective trends of hybrid microfluidic systems involving the improvement of fabrication techniques and broader applications are also discussed at the end of the review.

Predicting Drug Interactions to Unassociated Biomedical Implants Using Machine Learning Techniques and Model Polymers

Affinity based drug delivery mechanisms increase efficacy and minimalize off target effects when compared to non-specific methods due to the localization of drugs within target areas. While this is beneficial for targeted delivery, introduction of foreign polymeric medical devices into the body provide a potential area of localization due to high affinity between administered drugs and polymers. Previous attempts at creating models to predict affinity between small molecule drugs and polymers require a specific model be trained for each individual polymer failing to incorporate input features of both the polymer (host) and small molecule drug (guest). Within, we propose a universal model built using a neural network and quantitative structure activity relationships to predict the binding energy between guest and host molecules using input features. The trained model returned a correlation value, R2, of 0.9806 and 0.9958 between predicted and experimental binding affinity for the training and validation sets, respectively. This correlates to a mean absolute error of 0.951 kJ/mol and 0.771 kJ/mol for the training and validation sets, respectively. While limited to the current polymers used to train the model, the dataset can be expanded, and models retrained for further applications.

Thin film molecularly imprinted polymer (TF-MIP), a selective and single-use extraction device for high-throughput analysis of biological samples.

Enhancing selectivity, reducing matrix effects and increasing analytical throughput have been the main objectives in the development of biological sample preparation techniques. A thin film molecularly imprinted polymer (MIP) is employed for extraction and analysis of tricyclic antidepressants (TCAs) as a model class of compounds in human plasma for the first time to reach the abovementioned goals. The thin film MIPs prepared on a metal substrate can be used directly for extraction from biological matrices with no sample manipulation steps and no pre-conditioning. This method was validated with good linearity (R2 > 0.99 in 1.0-500.0 ng mL-1 range), excellent accuracy (90% -110%) and precision (RSD % value less than 15%) in pooled human plasma samples (N = 3). The limits of quantitation (LOQ) for TCAs in plasma samples were between 1.0-5.0 ng mL-1 which are lower than the therapeutic ranges of these drugs. Kinetic and isotherm studies showed the superior performance of MIP sorbent compared to a non-imprinted polymer (NIP) sorbent in extracting TCAs from a bovine serum albumin (BSA) solution. The optimized and validated method for pooled human plasma was utilized for monitoring the concentration of TCAs in three patient samples who had been prescribed TCAs. These selective single-use thin film extraction devices are promising for efficient and fast procedures for analyzing biological samples.

ArF-excimer laser as a potential tool for manufacturing of biomedical polymeric devices

ArF-excimer laser as a potential tool for manufacturing of biomedical polymeric devices

Naked-Eye Food Freshness Detection: Innovative Polymeric Optode for High-Protein Food Spoilage Monitoring

An innovative smart label for naked-eye protein food freshness evaluation, based on polymeric sensing films, is presented. The proposed device consists of six miniaturized sensors, obtained by covalently binding six pH indicators, namely, m-cresol purple (1), o-cresol red (2), bromothymol blue (3), thymol blue (4), chlorophenol red (5), and bromophenol blue (6), to an ethylene vinyl alcohol (EVOH) copolymer. All of the synthetic procedures for the functionalized polymers and their application as smart labels are thoroughly described and discussed. The innovative sensors are characterized using several instrumental techniques (DSC, FT-IR, EDX, SEM, and UV–vis). The application of the array of sensors to poultry meat and cod fillet spoilage monitoring by naked-eye evaluation and modeling by PCA is presented. Eventually, the composition of the food and the food’s headspace in the selling tray is investigated and qualitatively characterized to validate the attributes of the array of sensors. The polymeric devices seem to be very promising for industrial scale-up, with the starting EVOH copolymer being extrudable and already employed in food packaging, as well as for large-scale application, being clear, efficient, and easy to read, even by untrained people.

Triazine and Porphyrin-Based Cross-Linked Conjugated Polymers: Protonation-Assisted Dissolution and Thermoelectric Properties

As two pivotal functional segments, triazine and porphyrin can be coupled to form a highly cross-linked conjugated polymer. Although the obtained conjugated polymers are almost insoluble in most so...

Impact of polymerization and storage on the degree of conversion and mechanical properties of veneering resin composites.

To investigate the degree of conversion (DC), Martens hardness (HM), elastic indentation modulus (EIT), and flexural strength (FS) of veneering resin composites (SR Nexco Paste (NP), Ceramage Incisal (CI), Gradia Plus (GP); n=60/group) cured with different polymerization devices (bre.Lux Power Unit, Labolight DUO, Otoflash G171, LC-3DPrint Box, PCU LED; n=12/subgroup) after storage. Otoflash G171 and Labolight DUO showed increased DC/HM/EIT. CI presented the lowest DC and highest HM/EIT. NP showed the highest DC and lowest HM/EIT. Within Otoflash G171, Laboligth DUO and PCU LED, highest FS was observed for CI. Storage did not affect DC/HM/EIT for specimens cured with Otoflash G171 or Labolight DUO. With storage not showing an influence on the tested parameters for polymerization devices that otherwise presented superior results, increased storage time cannot be recommended. For the tested resin composites, this study observed a high/low degree of conversion to coincide with respectively low/high amounts of fillers/mechanical properties.

Homogeneous chemical state of self-doped polyaniline sub-micrometer thickness lines fabricated by fountain-pen lithography

The fabrication of molecular films by coating a conductive polymer solution on a substrate is an active topic in molecular electronics research. Since the inhomogeneity of polymer thin films modulates the chemical states and electrical properties of these films, the construction of integrated polymer devices requires methods to fabricate controllable, homogeneous molecular films as small patterns. Herein, we report the reproducible fabrication of sub-micrometer thickness self-doped polyaniline lines with high homogeneity by fountain-pen lithography (FPL). Compared with commonly used drop-casting and spin-coating methods, the fabrication of line patterns by FPL allows good control of line size, chemical/micro structures, and electronic properties, as demonstrated here by microscope Raman spectroscopy and conductance measurements. Supplying an identical amount of solution from a nanopipette and rapid solvent evaporation are likely crucial for fabricating homogeneous line patterns. This method is promising for the development of molecular electronic devices and the characterization of polymeric materials.

Fabrication of Transparent Polymer Optical Device Combined with Selective Visible-Light Transmission and Zero-Birefringence.

The formation of optical products using the traditional molten processing methods is a direct and extensive application of optical fields, and it suffers from intrinsic birefringence and optical distortion due to polymer orientation and residual stress. Here, a unique concept is proposed by assembling photonic crystal nanospheres without orientation in a rubbery state to realize transparent optical devices with zero-birefringence and high transparency. By developing fabrication techniques for transparent zero-birefringence optical devices, certain outstanding performances are realized, including no optical distortion and excellent mechanical properties. Simultaneously, by controlling the particle size of the photonic crystal, one has successfully obtained transparent optical devices with the visible light selective transmission are successfully obtained. The transparent zero-birefringence optical devices are promising candidates for potential applications for fine optical devices. The work opens up an exciting new fabrication route for zero-birefringence and highly transparent polymer devices that have been difficult to create using traditional methods.

Versatile Accumulated Surface Plasmon Resonance of Functionalized Nanosilver in Polymer Devices

The coupling effect of surface plasmons of noble-metal nanoparticles with excitons in organic materials enhanced the efficiency of devices (organic light-emitting diodes (OLEDs)). PEGylated graphen...

A Solution Processable Dithioalkyl Dithienothiophene (DSDTT) Based Small Molecule and Its Blends for High Performance Organic Field Effect Transistors.

The 3,5-dithiooctyl dithienothiophene based small molecular semiconductor DDTT-DSDTT (1), end functionalized with fused dithienothiophene (DTT) units, was synthesized and characterized for organic field effect transistors (OFET). The thermal, optical, electrochemical, and computed electronic structural properties of 1 were investigated and contrasted. The single crystal structure of 1 reveals the presence of intramolecular locks between S(alkyl)···S(thiophene), with a very short S-S distance of 3.10 Å, and a planar core. When measured in an OFET device compound 1 exhibits a hole mobility of 3.19 cm2 V-1 s-1, when the semiconductor layer is processed by a solution-shearing deposition method and using environmentally acceptable anisole as the solvent. This is the highest value reported to date for an all-thiophene based molecular semiconductor. In addition, solution-processed small molecule/insulating polymer (1/PαMS) blend films and devices were investigated. Morphological analysis reveals a nanoscopic vertical phase separation with the PαMS layer preferentially contacting the dielectric and 1 located on top of the stack. The OFET based on the blend comprising 50% weight of 1 exhibits a hole mobility of 2.44 cm2 V-1 s-1 and a very smaller threshold voltage shift under gate bias stress.

Development and in vivo Assessment of a Rapidly Collapsible Anastomotic Guide for Use in Anastomosis of the Small Intestine: A Pilot Study Using a Swine Model.

Various conditions in human and veterinary medicine require intestinal resection and anastomosis, and complications from these procedures are frequent. A rapidly collapsible anastomotic guide was developed for small intestinal end-to-end anastomosis and was investigated in order to assess its utility to improve the anastomotic process and to potentially reduce complication rates. A complex manufacturing method for building a polymeric device was established utilizing biocompatible and biodegradable polyvinylpyrrolidone and polyurethane. This combination of polymers would result in rapid collapse of the material. The guide was designed as a hollow cylinder composed of overlaying shingles that separate following exposure to moisture. An in vivo study was performed using commercial pigs, with each pig receiving one standard handsewn anastomosis and one guide-facilitated anastomosis. Pigs were sacrificed after 13 days, at which time burst pressure, maximum luminal diameter, and presence of adhesions were assessed. Burst pressures were not statistically different between treatment groups, but in vivo anastomoses performed with the guide withstood 10% greater luminal burst pressure and maintained 17% larger luminal diameter than those performed using the standard handsewn technique alone. Surgeons commented that the addition of a guide eased the performance of the anastomosis. Hence, a rapidly collapsible anastomotic guide may be beneficial to the performance of intestinal anastomosis.

Development and In Vitro Evaluation of Polymeric Responsive Release Matrix Type Transdermal Patches of Two Anti-asthmatic Drugs

Ketotifen fumarate, a mast cell stabilizer, and salbutamol sulfate, a bronchodilator, are frequently prescribed together for chronic asthma. This study aimed to combine both anti-asthmatic drugs in single polymeric responsive matrix type transdermal patches. Drug release from polymeric device was optimized by varying ratios of hydrophilic (polyvinyl pyrrolidone) and hydrophobic (ethyl cellulose) polymers. Propylene glycol was used as plasticizer and solvent system including mixture of chloroform and methanol. Physicochemical evaluations like thickness, weight variation, folding endurance, tensile strength, content uniformity and % moisture absorbance of developed patches were carried out. Developed patches were also subjected for in vitro release of drugs, and formulation of P6 with equal proportion of polyvinyl pyrrolidone and ethyl cellulose found optimized formulation with respect to release rate of both drugs. 76.49% of ketotifen fumarate and 77.49% of salbutamol sulfate were released from P6, and release of both drugs sustained up to 24 h. In the next step, permeability enhancers like Tween 20, isopropyl myristate, eucalyptus oil and span 20 were added to the formulation P6 and subjected to in vitro permeation study on Franz diffusion cell using rabbit skin. Results of in vitro permeation study revealed that transdermal patches with permeation enhancers permeate the significant amount of drugs in comparison with the formulation without enhancer.

Coplanar Electrode Polymer Modulators Incorporating Fluorinated Polyimide Backbone Electro-Optic Polymer

High-speed coherent optical communication has been expanding to handle the ever-increasing data traffic, and the large modulation bandwidth of electro-optic (EO) polymer modulators has been especially appreciated. However, to be useful in optical communication, the EO polymer device should address several issues, such as thermal stability, photo-oxidation, and bias drift. In this work, as a part of the experiments to address these challenges, an EO polymer with a fluorinated polyimide backbone is utilized to create EO polymer modulators with improved thermal stability. A coplanar electrode structure is introduced to enhance the poling efficiency and reduce the bias drift.

Analysis of optical linearity and nonlinearity of Fe3+- doped PMMA/FTO polymeric films: New trend for optoelectronic polymeric devices

Iron-doped polymethylmethacrylate (Fe3+/PMMA) films were deposited on FTO glass substrates. X-ray diffractometer (XRD), Fourier-transform infrared spectroscopy (FT-IR) were applied to examine the structure of Fe3+/PMMA/FTO films with varying doping percentages of iron-ions. The obtained XRD diffraction results proved the uniform and semi-crystalline in nature of the tested samples. The vibrational modes of both metal-ions and host PMMA polymers were respectively observed at 450 and 980 cm−1. The direct optical energy bandgaps for the proposed undoped and Fe3+-doped PMMA thin films were valued to be approximately 4.11, 4.1004, 4.094, 4.087, 4.07, 3.801, and 3.35 eV. The indirect energy bandgaps were 3.605, 3.58, 3.55, 3.504, 2.85, and 2.37 eV with increasing the Fe3+-contents, respectively. Moreover, the optical limiting of Fe3+/PMMA/FTO films was studied through red He-Ne and green diode lasers operating at 632.8 and 532 nm, correspondingly. Finally, Fe3+-doped PMMA/FTO composites are considered an excellent candidate for various optoelectronic devices.

Recent advances in flexible PVDF based piezoelectric polymer devices for energy harvesting applications

Energy harvesting is one of the most promising research areas to produce sustainable power sources from the ambient environment. Which found applications to attain the extensive lifetime self-powered operations of various devices such as MEMS wireless sensors, medical implants and wearable electronic devices. Piezoelectric nanogenerators can efficiently convert the vastly available mechanical energy into electrical energy to meet the requirements of low-powered electronic devices. Among the piezoelectric materials, poly (vinylidene fluoride) (PVDF) and its copolymers are extensively studied for the development of energy harvesting devices. Due to the outstanding properties such as high flexibility, ease of processing, long-term stability, biocompatibility makes them a promising candidate for piezoelectric generators. Nevertheless, compared to piezoceramic materials, PVDF based generators produce lower piezoresponse. Over the last decades, tremendous research activities have been reported to endorse the performance of PVDF based energy harvesters. This review article mainly focused on the recent progress in the performance improvement with processing methods, piezoelectric materials, different filler loading. The new developments and design structures will lead to an increase in piezoelectricity, alignment of dipoles, dielectric properties and subsequently enhance the output performance of the device. Electronic circuits play a vital role in energy harvesting to efficiently collect the developed charge from the device. Here, we have proposed a detailed description of the electronic circuits. Also, in the application part deals with the recent progress in flexible, biomedical and hybrid generators based on PVDF polymers.

Porous thin-film molecularly imprinted polymer device for simultaneous determination of phenol, alkylphenol and chlorophenol compounds in water

A porous water-compatible molecularly imprinted polymer (MIP) coating using catechol as a pseudo-template and a water-soluble functional monomer (4-vinyl benzoic acid) with ethylene glycol dimethacrylate as the crosslinker was developed for extraction of phenols from environmental water samples. The MIP devices were combined with ultra high performance liquid chromatography with a photodiode array detector (UHPLC-PDA) suitable for the simultaneous determination of trace levels of phenolic compounds with a wide range of polarities —phenol, alkylphenols and chlorophenols— in seawater and produced water. Parameters that influence extraction efficiency (salinity, pH, polymer mass, desorption solvent, and desorption time) were optimized to give method detection limits (LOD) ranging from 0.1 to 2 μg L−1 and linearity (R2>0.99) over at least three orders of magnitude for the hydrophobic phenols (e.g., 0.5–1000 μg L−1 for 2,4,6-trichlorophenol) and ~2 orders of magnitude for the light phenols (e.g., 10–120 μg L−1 for phenol, 5–120 μg L−1 for methylphenols and 2-chlorophenol, 0.5–120 μg L−1 3-methyl-4-chlorophenol and 2,4-dichlorophenol). The recoveries from authentic spiked samples ranged from 85 to 100% with %RSDs of 0.2–14% for seawater and 81–107% with %RSD of 0.1–11% for produced water. The resulting MIP-based extraction requires no pre-conditioning of the sorbent, and because the required sample size is small and sample manipulation is limited, the method is easy to multiplex for high throughput sample processing.

Polymers in high-intensity focused ultrasound fields

High-intensity focused ultrasound (HIFU) is a promising stimulus that has received extensive attention during the past two decades due to numerous advantages of this technology when compared to the conventional methods. For HIFU-responsive polymers, their applications could be extended to controlled drug delivery, soft robotics, and flexible electronics. In this work, experiments show that polymers heat up in a different manner when they are subjected to HIFU, compared to the case they are subjected to heat sources directly. However, the origins of this difference are still entirely unknown. To further investigate, molecular dynamics (MD) simulations are performed to study the thermal effect of polymers induced by HIFU. We found the difference in the macroscale response of polymers subjected to HIFU strongly depends on the polymer chains, composition, and structure. The frequency-dependent viscoelasticity, measured by stress-strain phase lag, the reputation motion of the chains, and the vibration-induced local mobility, quantified by the root mean square fluctuation (RMSF) contribute to the observed difference in the HIFU-induced thermal effects. The simulation results show a good accordance with the experiment qualitatively, and provide the fundamental mechanism for designing and optimizing stimuli-responsively polymeric devices. [Work supported by: this work was supported by NSF Grant No. CMMI-2016474.]