Surface Area Of Film Research Articles

The effects of aspect ratio of cellulose nanocrystals on the properties of all CNC films: Tunicate and wood CNCs

In this study, the physicochemical, mechanical, and thermal properties of films made from cellulose nanocrystals (CNCs) obtained from two sources – wood and tunicate - and their hybrids were investigated. It was found that different morphologies affect the properties of CNC films. Specifically, the surface morphology of tunicate CNC (TCNC) films differed significantly from wood CNC (WCNC) films, and the structure of hybrid CNC (HCNC) films was also different. Compared to wood CNC-containing films, tunicate CNC films exhibited significantly higher BET surface areas, superior thermal properties, greater surface roughness, and very low (≈1 wt.%) dispersibility in water due to their ability to form long-range connectivity. The average BET surface area of TCNC films was measured at 91.9 ± 2.1 m2/g, and this value decreased with the addition of WCNCs to the film structure. The pore diameter also decreased from 11.362 nm for TCNC films to 0.437 nm for WCNC films, indicating the filler effect of WCNCs on the TCNC films. The chiral nematic phase exhibited by WCNC films was confirmed by their iridescent appearance, as observed through cross-sectional SEM images. The TS for TCNC and HCNC3 was measured at 185.2 ± 10.5 MPa and 182.9 ± 13.7 MPa, respectively, which were the highest values among the samples. The lowest TS value of 113.1 ± 9.5 MPa was observed in the WCNC films. A similar decline was observed in the EB values, from 1.76 ± 0.37% for TCNC to 0.9 ± 0.22% for WCNC. This study provides information and knowledge useful for understanding the impact of biomass source on the properties of CNC films for a variety of purposes, including packaging materials, biodegradable coatings, flexible electronics, and membrane applications.

Triboelectric Film with Electrochemical Surface Modification for Multiple Mechanical Energy Harvesting with High Storage Efficiency and Sensing Applications

Triboelectric nanogenerators (TENGs) are a key technology that can harvest mechanical energy available from the surrounding nature into electricity based on the triboelectrification and electrostatic induction mechanism. Rotational energy is one of the abundantly available renewable energy sources that can efficiently be harvested into electricity. It is also well-known that the surface area of the triboelectric film plays an important role in electric output generation. Herein, we electrochemically modified the surface of a copper film by creating microarchitecture and employed it in the fabrication of a rotational TENG (R-TENG). The fabricated R-TENG generated an electrical output of ∼180 V and ∼11 μA at 100 rotations per minute. Thereafter, the generated electrical output was efficiently stored by fabricating and combining a circuit with the R-TENG. Finally, the R-TENG was used to harvest various rotational energies, and the produced electric output was used to power portable electronics. The R-TENG combined with the circuit also functions as a wind speed sensor.

Decomposition of Fingerprints on Porous TiO2 Thin Films

This study investigated the effect of the mixing ratio of TiO2 nanoparticles (P25) and titanium alkoxide (T-sol) on various properties of TiO2 films. The specific surface area of the TiO2 film was determined using BET analysis, while the microstructure and thickness were analyzed by field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM), respectively. Transmittance and pencil hardness tests were conducted to evaluate the transparency and durability of the coating layer, respectively. The results showed that, as the P25 content increased, the specific surface area of the TiO2 film also increased, but this effect decreased as the ratio of T-sol to P25 increased. Additionally, the thickness and surface roughness (Ra) of the coating layer increased as the P25 content increased, with the thickness increasing from 210 to 950 nm and Ra increasing from 51 to 88 nm. However, the transmittance of the coating layer decreased as the P25 content increased, indicating that the films became less transparent. Furthermore, the pencil hardness of the coating layer decreased as the P25 content increased, indicating that the films became less durable. Finally, the oil contact angle decreased as the P25 content increased, indicating that the films became more hydrophilic.

Study of ZnO nanosheets growth parameters effect on the performance of the triboelectric nanogenerator

Herein, we report the effect of ZnO thin film morphology on triboelectric nanogenerator (TENG) performance. The ZnO nanostructures were synthesized by a hot-plate method, which is an easy, inexpensive, low-temperature, and fast- process. We used ZnO film and PET as frictional layers to fabricate the TENG device. ZnO films that were synthesized at various growth temperatures and growth durations were used to test the TENG's output. It was observed that TENG output increased with ZnO films synthesized at higher growth temperatures and growth duration. This enhancement in the output can result from a change in the effective contact surface area of the ZnO film with PET. The maximum peak-to-peak voltage and short circuit current of ∼ 15 V and ∼ 20 µA were obtained for ZnO films synthesized at a temperature of 90 °C for 4 hrs. The resulting TENG displays consistent current output across 598 cycles, demonstrating the TENG's excellent level of stability.

The velocity field characteristics of high‐viscosity fluids falling film flow down clamped channels

AbstractThe complexity of falling film flow has been studied in many industrial applications. In this work, the velocity field of high‐viscosity fluids falling film flow down clamped channels was investigated numerically and experimentally. The results show that the numerical simulation results are consistent with the experimental results, and the characteristics of the velocity field are related to the fluid properties, operating conditions, and structure of the clamped channels. When the fluid viscosity is greater than or equal to 10 Pa ⋅ s, the type of velocity field changes into I shape, U shape, and V shape. While the fluid viscosity drops to 0.89 Pa ⋅ s, the viscous force cannot resist the inertial force and gravity, resulting in a cardioid velocity field. By adjusting the structure of the clamped channels and operating conditions, the tension of the liquid film can be changed, and the velocity distribution of the liquid film can be manipulated. Significantly, under the fluctuating curtain flow, the liquid film coalesces and breaks frequently, which enlarges the surface area of the liquid film and strengthens the surface renewal frequency. Hence, this form of falling film flow can be applied to process intensification of high‐viscosity materials.

A "turn-on" inverse opal photonic crystal fluorescent sensing film for detection of cysteine and its bioimaging of living cells.

A "turn-on" inverse opal photonic crystal fluorescent sensing film infiltrated with a coumarin derivative is reported for the reliable and accurate detection of cysteine in human serum and fluorescence imaging of living cells. The coumarin derivative containing allyl ester specifically reacts with cysteine by ammonolysis to generate a fluorescent product whose emission wavelength is at ~ 535nm, providing a selective fluorescence detection for cysteine. The emitted fluorescence is significantly enhanced due to the slow photon effect derived from the photonic crystal film. This is because the emission wavelength is overlapped with the blue-band edge of the photonic stopband of the selected inverse opal film. The fluorescence enhancement effect endows the prepared inverse opal film with highly sensitive detection with a limit of detection of 3.23 × 10-9mol/L and a wide linear detection range of 1 × 10-7 - 1 × 10-3mol/L. A fast response within 30s toward cysteine is also achieved due to the three-dimensional interconnected macroporous structure with a high-specific surface area of the inverse opal film. The prepared inverse opal fluorescent sensing film has been successfully applied to the detection of cysteine in human serum and bioimaging of living cells. In the diluted human serum, the recoveries for the detection of cysteine were 97.92 - 107.20%, and the relative standard deviations were 2.61-9.04%, demonstrating the potential applicability of the inverse opal fluorescent sensing film to real sample analysis. The method may provide a universal strategy for constructing various photonic crystal fluorescent sensing films by using different fluorescent probes.

Disposable Wearable Sensors Based on Nanocellulose for Biomedical Applications

Monitoring of human motor and muscle activity is used in many areas, from prosthetics during rehabilitation to training monitoring of athletes. Sensors for these tasks are usually made of flexible polymers and require recycling after the expiration date. Nanocellulose (NC) can be used as a biodegradable base for this type of sensor. The development of low-cost disposable sensors that do not require disinfection and cleaning is relevant. NC is a composite nanoscale structure of cellulose fibers (fibrils) with a high aspect ratio. The paper aim is to develop disposable wearable biodegradable bend sensors based on nanocellulose using vacuum synthesis methods and the study of their characteristics. Nanocellulose was synthesized by the TEMPO method. The sensors were created by means of magnetron sputtering of Ti/Ni or Cr/Ni thin films at the surface of nanocellulose. Measuring stand was developed to determine the change in resistance due to the bending of the sensor. It’s mechanical part consists of an elastic deformation plate made of high-alloy steel, which can be bent using a micrometric screw. The change in resistance is linearly related to the elongation of the measured sample. A Wheatstone bridge and a 24-Bit ADC HX711 were used to measure the change in resistance. During testing of the sensor for analysis of muscle activity, the sensor element was attached to the human skin with the help of medical glue BF-6. The obtained sensors were tested for biodegradability. The samples were placed in the ground at a depth of 20-30 mm. The mass of nanocellulose samples was measured using a high-precision digital balance EDIS 50 (50/0.001 g) with a built-in level. The optimal ratio of the value of sensitivity and reversibility is observed in the range of the nominal resistance of the nickel film from 10 to 100 Ohms. This is due to an increase in the surface area of ​​the Ni film, which leads to an increase in sensitivity, but at the same time there is a decrease in the repeatability of the characteristics due to a greater influence of the heterogeneous structure of nanofibrillated cellulose. In addition, sensors with different buffer layer materials - Ti and Cr - were selected for testing. For titanium-based sensors, the maximum sensitivity coefficient is 0.312%, while the deviation of the sensor signal after one bending-unfolding cycle (reversibility) is less than 0.001%. Chromium-based sensors have significantly higher sensitivity (0.9753%), but worse reversibility (7.14%). Sensors based on the Cr buffer layer showed poorly reproducible results in the cyclic mode of operation, namely: there are significant fluctuations in the signal amplitude (up to 50-60%) already after the second bending-unfolding cycle. Therefore, despite the high sensitivity of such sensors, they are unsuitable for analyzing human motor and muscle activity/ The sensors based on the Ti buffer layer showed good response (2.5-3%) and good repeatability and resistance to cyclic bending (30 times). It can be seen that the obtained dependencies are approximated by a linear law. Some deviation from linearity is obviously related to the inhomogeneity of the Ni thin film. Also, the sensors showed a good loss of mass (40% in 9 weeks) during the biodegradability test, which confirms their ability to decompose under the influence of atmospheric phenomena. So, in this work, disposable wearable sensors on a nanocellulose substrate were synthesized for the evaluation of motor and muscle activity of a person. It was found that such sensors can be used to test of finger and biceps movement during at least 10-30 full flexion-extension cycles. For test of elbow movement, it is planned to synthesize a high-elastic composite material based on nanocellulose and bioelastic material (for example, polyvinyl alcohol). Thus, the proposed sensor manufacturing technology makes it possible to obtain cheap, light, flexible disposable wearable sensors that do not require further disposal after the end of operation.

Nanoporous Au Formation on Au Substrates via High Voltage Electrolysis.

Nanoporous Au (NPG) films have promising properties, making them suitable for various applications in (electro)catalysis or (bio)sensing. Tuning the structural properties, such as the pore size or the surface-to-volume ratio, often requires complex starting materials such as alloys, multiple synthesis steps, lengthy preparation procedures or a combination of these factors. Here we present an approach that circumvents these difficulties, enabling for a rapid and controlled preparation of NPG films starting from a bare Au electrode. In a first approach a Au oxide film is prepared by high voltage (HV) electrolysis in a KOH solution, which is then reduced either electrochemically or in the presence of H2 O2 . The resulting NPG structures and their electrochemically active surface areas strongly depend on the reduction procedure, the concentration and temperature of the H2 O2 -containing KOH solution, as well as the applied voltage and temperature during HV electrolysis. Secondly, the NPG film can be prepared directly by applying voltages that result in anodic contact glow discharge electrolysis (aCGDE). By carefully adjusting the corresponding parameters, the surface area of the final NPG film can be specifically controlled. The structural properties of the electrodes are investigated by means of XPS, SEM and electrochemical methods.

Ensuring the uniformity of oscillations of a flat membrane by sources of ultrasonic impact

The article presents the results of studies aimed at ensuring the uniformity of vibrations of a flat membrane by sources of ultrasonic exposure. The relevance of the conducted research lies in the fact that for the effective implementation of physical and physicochemical processes in thin liquid films, it is necessary to ensure the maximum uniformity of the effect over the entire surface area of the spreading film. The main problem is that today there are no ultrasound emitters that are able to form a uniform distribution of vibrations over the entire impact plane and thereby ensure the uniformity of the technological process. The vibration concentrators and reciprocating working tools that currently exist are distinguished by a limited radiation surface. This is due to the fact that attempts to increase the area of the radiating surface lead to the need to use multipackage piezoelectric transducers. However, in this case, it is not possible to ensure the in-phase oscillations of each packet (due to wave processes inside the emitter material) and, therefore, for large surface areas, the oscillations turn out to be inhomogeneous or have a small amplitude. The authors propose a mathematical model that will allow optimizing the location of the emitters to ensure maximum uniformity of oscillations of a flat surface. The proposed model makes it possible to identify the optimal configurations of radiators, which provide the smallest dispersion of the oscillation amplitude of the free surface (on which there are no fixed radiators).

Theoretical Investigation of Wenzel and Cassie Wetting States on Porous Films and Fiber Meshes.

In this study, the wetting phenomenon on a thin, porous film covering a substrate was investigated on the basis of a classical equilibrium theory. The equilibrium contact angles of the Wenzel, hydrophobic Cassie, and hydrophilic Cassie states and the transition points between them were derived as functions of parameters, such as the porosity and specific surface area of the porous film. These expressions were applied to describe wetting on fiber mats/meshes. The equilibrium contact angles and transition points of the three wetting states on the fiber mesh covering the substrate are expressed as functions of parameters, such as fiber radius, roughness factor, and volume porosity of the fiber mesh. A fiber mesh can attain superhydrophobicity when it is composed of thin hydrophobic fibers with surface roughness and has an appropriate volume porosity.

Boosting performance of triboelectric nanogenerator via polydimethylsiloxane modified with perovskite BiFeO3 nanoparticles

ABSTRACT Triboelectric nanogenerators (TENGs) have great potential applications in the field of microelectronics. However, the low surface charge density of the triboelectric layer is one of the key problems greatly limiting its output performance. Herein, we report a high-performance TENG using BiFeO3@polydimethylsiloxane (BFO@PDMS) composite film as a triboelectric layer. The results indicate that doping a small amount of BFO particles can significantly increase the dielectric constant and surface area of the PDMS film, which maximises the surface charge density of the triboelectric layer. With an optimized doping concentration , the dielectric constant of BFO@PDMS composite film is 14.2% higher than that of the pure PDMS film. The BFO@PDMS-based TENG delivers a maximum output voltage and current of 180 V and 30 μA, corresponding to 200% and 500% increases compared with pure PDMS film, respectively, which can drive an electronic watch and light 52 LEDs, indicating potential applications in microelectronic devices.

3D porous graphene/double-walled carbon nanotubes/gold nanoparticles hybrid film for modifying electrochemical electrode

3D porous graphene/carbon nanotubes (Gr/CNTs) hybrid films containing nanoparticles have introduced new possibilities for the development of high-performance electrochemical sensors. Herein, we developed a novel technique for the fabrication of 3D porous graphene/double-walled carbon nanotubes/gold nanoparticles (Gr/DWCNTs/AuNPs) hybrid film on copper foils by using the thermal chemical vapor deposition (CVD) method. On these porous films, DWCNTs, Gr winkles, and a homogeneous AuNP covering were observed. These prepared 3D porous films were then transferred onto the surface of screen-printed electrodes (SPE) to investigate the electrochemical properties by using cyclic voltammetry (CV) technique. Consequently, 3D porous Gr/DWCNTs/AuNPs film modified electrodes exhibited good electrochemical characteristics with an active surface area of 2.76 times higher than that of Gr/DWCNTs film. This is due to the use of AuNPs, which improves the conductivity and surface area of the porous film.

Characterization of multifunctional solution-processed Sn1-xZnxS nanostructured thin films for photosensitivity and photocatalytic applications

Zinc (Zn) doped/substituted Tin(II) sulfide (SnS) is one of the most important semiconductors for optoelectronic, photocatalytic, and gas-sensing applications. Herein, an ultra-fast, highly efficient and room temperature operated photocatalyst degrading powerful organic dyes under direct exposure to the UV–Vis/Sun-light and photo sensor based on Sn1-xZnxS (x = 0.00–0.20) nanostructured thin films were fabricated for the first time by using facile solution process. Compared to the SnS the crystallite/grain size, absorption, active surface area, absorption/reflectivity intensity, photoluminescence, and electrical conductivity of the Sn1-xZnxS thin films were improved considerably at a certain substitution level of Zn (at. %1) according to XRD, SEM, XPS, Raman, UV–Vis spectroscopy, Photoluminescence (PL), and electrical analysis. Amongst all, the Sn0.99Zn0.01S exhibits the highest photocatalytic efficiency (100% for 25 min) for degradation of MB at pH = 11 under sunlight at room temperature, which is higher than the most reported efficient photocatalyst based on SnS thin films whilst it shows 97% photocatalytic efficiency under the UV–Vis-light (at pH = 4, for 210 min) according to photocatalytic measurements. The observed highest values have been attributed to the synergic effect of pH and the highest crystallite size of the photocatalyst. Moreover, the Sn0.99Zn0.01S film sample also has the highest photosensitivity response (225%) with a decay time of 1.06 s amongst all the SnS and Zn-substituted SnS thin films due to having higher crystallite size and hence having more active crystallite site for the other Zn-substitution levels. These outcomes make the Zn-substituted SnS thin films promising and highly efficient multifunctional materials for photocatalytic, photosensitivity, and optoelectronic applications.

Graphene coupled MoO3 films prepared by wetting-induced climbing and key role of graphene on photocatalytic activity enhancement

Because of its unique physical and chemical characteristics, such as excellent electrical conductivity, wide-range light absorption, and strong chemical adsorption, graphene was used to couple with the MoO3 films prepared by anodization followed by annealing to improve their photocatalytic performance using a novel thin-film composite method, called the wetting-induced climbing method. These composite films were analyzed by XRD, SEM, XPS, UV–vis spectroscopy, and EIS spectra. The XRD, SEM, and XPS analysis results show that the graphene/MoO3 composite films were prepared. The light absorption capacity of these composite films was greatly enhanced. The bandgap values were decreased due to the graphene coupling and crystal defects in the MoO3 films. The EIS spectra indicate that the photogenerated charge carriers were easier to transfer to the coupled graphene, which worked as the acceptor and transferred medium of photo-induced electrons owing to the graphene coupling. The graphene coupling amount has a moderate and optimum value to improve photocatalytic activity. Too many graphene platelets would shield the greater surface area of MoO3 films and thus reduce the number of photo-inspired carriers, leading to fewer oxidizing species. The number reduction of graphene layers has no positive effect on improving photocatalytic activity. The photocatalytic activity of the graphene/MoO3 composite films is 2.62 times that of the individual MoO3 films.

Stretchable, self‐healable, and breathable biomimetic iontronics with superior humidity‐sensing performance for wireless respiration monitoring

AbstractStretchable, self‐healing, and breathable skin‐biomimetic‐sensing iontronics play an important role in human physiological signal monitoring and human–computer interaction. However, previous studies have focused on the mimicking of skin tactile sensing (pressure, strain, and temperature), and the development of more functionalities is necessary. To this end, a superior humidity‐sensitive ionic skin is developed based on a self‐healing, stretchable, breathable, and biocompatible polyvinyl alcohol–cellulose nanofibers organohydrogel film, showing a pronounced thickness‐dependent humidity‐sensing performance. The as‐prepared 62.47‐μm‐thick organohydrogel film exhibits a high response (25,000%) to 98% RH, excellent repeatability, and long‐term stability (120 days). Moreover, this ionic skin has excellent resistance to large mechanical deformation and damage, and the worn‐out material can still retain its humidity‐sensing capabilities after self‐repair. Humidity‐sensing mechanism studies show that the induced response is mainly related to the increase of proton mobility and interfacial charge transport efficiency after water adsorption. The superior humidity responsiveness is attributed to the reduced thickness and the increased specific surface area of the organohydrogel film, allowing real‐time recording of physiological signals. Notably, by combining with a self‐designed printed circuit board, a continuous and wireless respiration monitoring system is developed, presenting its great potential in wearable and biomedical electronics.

Soil refinement accelerates in-field degradation rates of soil-biodegradable mulch films

Soil-biodegradable mulch films are a promising solution to replace conventional polyethylene-based mulch films, the use of which has led to negative environmental impacts. Soil-biodegradable mulch films are specifically designed to be incorporated into the soil at the end of the cropping cycle, and are expected to be biodegraded by soil microorganisms. The biodegradability of such products must be tested under laboratory-controlled conditions following international standards, although these can fail to represent real environmental conditions where mulch films are used. The objective of this study was to evaluate the effects of soil refinement on the degradation rates of three different commercial soil-biodegradable mulch films after their incorporation into the soil. The hypotheses were that: (i) soil refinement (i.e., ploughing followed by grubbing) creates more favourable conditions for film biodegradation compared to ploughing alone; and (ii) different mulch films show different degradation rates. An open-field completely randomised design was applied to test the effects of soil refinement by ploughing to 0.35 m depth without and with subsequent grubbing to 0.15 m depth twice. Three commercially available soil-biodegradable mulch films were sampled in 2020 (i.e., two Mater-bi-based, one Ecovio-based) at the end of a zucchini growing season (~3 months) when films were still lying above ground, and were later buried at 0.2 m depth inside mesh bags. Biodegradation rates of the sampled films were assessed with the indirect indicators of film weight loss and surface area loss at ~2-month intervals over 314 days. The results showed that soil refinement significantly accelerated degradation of the three tested mulch films by 14% and 17% according to the loss of weight and surface area indicators, respectively. One Mater-bi-based film showed higher degradation rates compared to the other two films. Future studies are needed to quantify the time needed for these different mulch films to be completely biodegraded. Such studies should be carried out following standards for laboratory incubation and/or in-field quantification of residual polymers in the soil over time. Highlights- Degradation rates of three biodegradable mulch films were evaluated in the open-field.- Soil refinement accelerates the degradation of film weight (14%) and surface (17%).- Highest degradation rates were observed for one Mater-bi-based film.- Fastest degradation rates were observed in spring for all the tested films.- Weight and surface area loss indicators showed positive relationship.

Electrochemical Impedance Spectroscopic Investigations of Nanocomposite Thin-Film Formation at an Electrified Micro Liquid-Liquid Interface

Herein, the interface between two immiscible electrolyte solutions (ITIES) has been exploited as a pristine platform for electropolymerization of the 2D and 3D nanocomposite materials, i.e., metal nanoparticles (NPs) embedded within a conductive polymer matrix that are electrogenerated/electropolymerized simultaneously The free-standing conductive thin film can be prepared with an adjustable loading of metallic NPs, to be tailored for a variety of applications, including as catalytic electrodes in fuel cells, or act as a bioreceptor in a biosensor. Electrochemical impedance spectroscopy (EIS) has been used to investigate mechanistic aspects of film growth through two types of charge transfer processes, ion and electron transfer, that occur during electropolymerization. The thermodynamics of a heterogeneous electron transfer (HET) between redox centers, KAuCl4(aq) and terthiophene (TT, org), across the interface governs the electropolymerization reaction, including the rate, which is itself affected by the rate of diffusion of reactants toward the interface, ohmic resistance of the two electrolyte solutions, distance between reactants due to arrangement of ions at the interface, and reorganization energy of the involved species in the reaction. Electropolymerization is controlled through application of an applied external potential difference and monitored voltammetrically as well as by EIS. Curve fitting of EIS data was performed using an equivalent circuit incorporating a phase constant element (CPE) parallel to a resistor for non-ideal interfacial capacitance, and HET resistance across the film as it forms at the ITIES. Next, those elements are parallel to a resistor (R), and a Warburg element (W) to approximate ion transfer across the ITIES/porous thin-film as it grows (Fig. 1). Data suggest that the films electronic conductivity improves with increasing the [TT]:[KAuCl4] ratio. Increased capacitance was hypothesized to be linked to an increase in the effective surface area of the polymer film during its growth phase versus the molecularly smooth ITIES. Higher [TT]:[KAuCl4] ratios elicited higher capacitance as well as diffusion resistance which can be attributed to formation of a more compact film structure. Cyclic voltammetric and potential step methods are compared and discussed, highlighting the formed films final properties, including film thickness and conductivity. Figure 1

Honeycomb-Structured Porous Films from Poly(3-hydroxybutyrate) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate): Physicochemical Characterization and Mesenchymal Stem Cells Behavior.

Surface morphology affects cell attachment and proliferation. In this research, different films made of biodegradable polymers, poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHB-co-HV), containing different molecular weights, with microstructured surfaces were investigated. Two methods were used to obtain patterned films—water-assisted self-assembly (“breath figure”) and spin-coating techniques. The water-assisted technique made it possible to obtain porous films with a self-assembled pore structure, which is dependent on the monomer composition of a polymer along with its molecular weight and the technique parameters (distance from the nozzle, volume, and polymer concentration in working solution). Their pore morphologies were evaluated and their hydrophobicity was examined. Mesenchymal stem cells (MSCs) isolated from bone marrow were cultivated on a porous film surface. MSCs’ attachment differed markedly depending on surface morphology. On strip-formed stamp films, MSCs elongated along the structure, however, they interacted with a larger area of film surface. The honeycomb films and column type films did not set the direction of extrusion, but cell flattening depended on structure topography. Thus, stem cells can “feel” the various surface morphologies of self-assembled honeycomb films and change their behavior depending on it.

Development of Intelligent Gelatin Films Incorporated with Sappan (Caesalpinia sappan L.) Heartwood Extract.

This study aimed to develop intelligent gelatin films incorporated with sappan (Caesalpinia sappan L.) heartwood extracts (SE) and characterize their properties. The intelligent gelatin film was prepared through a casting method from gelatin (3%, w/v), glycerol (25% w/w, based on gelatin weight), and SE at various concentrations (0, 0.25, 0.50, 0.75, and 1.00%, w/v). The thickness of the developed films ranged from 43 to 63 μm. The lightness and transparency of the films decreased with the increasing concentration of SE (p < 0.05). All concentrations of gelatin films incorporated with SE exhibited great pH sensitivity, as indicated by changes in film color at different pH levels (pH 1–12). Significant decreases in tensile strength were observed at 1.00% SE film (p < 0.05). The addition of SE reduced gelatin films’ solubility and water vapor permeability (p < 0.05). The chemical and physical interactions between gelatin and SE affected the absorption peaks in FTIR spectra. SE was affected by increased total phenolic content (TPC) and antioxidant activity of the gelatin film, and the 1.00% SE film showed the highest TPC (15.60 mg GAE/g db.) and antioxidant activity (DPPH: 782.71 μM Trolox/g db. and FRAP: 329.84 mM/g db.). The gelatin films combined with SE could inhibit S. aureus and E. coli, while the inhibition zone was not observed for E. coli; it only affected the film surface area. The result suggested that gelatin films incorporated with SE can be used as an intelligent film for pH indicators and prolong the shelf life of food due to their antioxidant and antimicrobial activities.

High surface area polymer films by co-crystallization with low-molecular-mass guest molecules

A general method to achieve high surface area (SA) films (SA in the range 45–620 m2/g), based on polymer co-crystallization with low-molecular-mass guests, is presented. The method requires fast guest-induced co-crystallization of amorphous polymer films, reaching high guest equilibrium contents (typically in the range 65–90 wt%), followed by fast guest removal from guest-reach co-crystalline films. This method is effective not only for polymers that by guest removal can lead to nanoporous-crystalline phases (like poly(2,6-dimethyl-1,4-phenylene)oxide, PPO and syndiotactic polystyrene, sPS) but also for polymers that by guest removal lead to usual dense crystalline phases (like polylactic acid, PLLA). These high SA films show guest uptakes at low activities which are high or negligible if the films exhibit nanoporous-crystalline (as for PPO and sPS) or dense phases (as for PLLA), respectively. Kinetic studies show that guest diffusivity can be increased by two or three orders of magnitude, going from amorphous to high SA NC films.