Papers by Keyword: PDMS

Abstract: The optimization stage of the PDMS/PVA-PEG hydrophilic sponge has been prepared to increase water absorption, through the addition of wetting agents including bentonite, silicon oil, silica gel, and sodium hydrogen carbonate. The bentonite is purified by magnetic separation with a montmorillonite (MMT) content of approximately 33,17%. Silicon oil has hydrophilic properties due to the high surface energy of silicon dioxide, while silica gel is an adsorbent that will produce high silanol groups, and NaHCO₃ is used to expand pores when releasing CO₂. PDMS/PVA-PEG hydrophilic sponges were prepared with various ratios (w/w) PDMS: silicone oil: silica gel: NaHCO₃: ZnCl₂: PVA: PEG= 1:2:2:2,5:5:5:10 (V1 sponge); 1:2:2:1.25:5:5:10 (V2 sponge); 1:2:2:0:5:5:10 (V3 sponge). The sponge synthesis process is conducted by heating at a temperature of 110°C for 4 hours. The hydrophilic sponge composite incorporated bentonite in a ratio of 1:1 (w/w) to obtain VB1 sponge, VB2 sponge, and VB3 sponge have contact angle values 37.0°, 56.6°, and 58.8°, respectively. NaHCO₃ can increase the pore of the sponge, therefore the condition can increase the hydrophilicity. The contact angle of V1 sponge is 45.2°, while VB1 is 37°.0°, which indicates that bentonite can enhance hydrophilic properties. Excellent wetting properties will imply good dewatering properties for hydrocarbon fuel refining.

Abstract: As a drug product for vitreous replacement, the stability of polydimethylsiloxane (PDMS) during storage is very necessary. PDMS must be stable both chemically and physically during the storage process according to WHO standards. This is necessary to maintain security and regulate the drug supply. Our research shows that low-and medium-viscosity PDMS produced from low-grade octamethylcyclotetrasiloxane (D4) monomer have good stability and storage for 15 months. The optimal time for stability and storage of this PDMS is 5 months. Changes in viscosity values occur due to a very slow chain growth from 5 until 15 months. However, a longer assessment time and other tests are needed to complete the material stability information.

Abstract: Conductive and flexible electronics have attracted great demands and attention in the field of stretchable and wearable electronic devices. In this work, polydimethylsiloxane (PDMS) was composited with different drops of graphene solution to produce flexible, conductive and optically transparent PDMS/Graphene composite using the drop-cast method. The dielectric constants of PDMS and PDMS/Graphene composite were measured using Agilent dielectric probe. I-V characterization was used to measure the conductivity of the flexible substrate in flat and bending conditions. The UV-VIS was used to measure the transmittance properties of the substrate. Comparing the electrical properties of the pristine PDMS substrate with graphene composited PDMS substrates, the current shows a slight decrease due to the physical morphology of PDMS/Graphene composite that creates a small hole on the surface. No significant changes can be found between 1 drop, 2 drops, 3 drops and 4 drops of graphene in PDMS solution. For the dielectric measurement, the result of composited PDMS/Graphene sample had shown a lower value of dielectric constant (1.1 F/m) compared to pure PDMS (2.33 F/m). This shows that the existence of graphene in PDMS reduces the dielectric constant of pristine PDMS. The result of UV-VIS shows the samples with 4 drops of graphene having the lowest visible transmittance. The PDMS/Graphene composite can be concluded as a dielectric material with a lower dielectric constant. It has the potential to be used as a conductive substrate for further flexible interconnect materials since it has a unique electrical feature and robust mechanical strength.

Abstract: – Over recent year, robotics has made a drastic impact in a variety of different markets. Although having many advantages from, safer workspace to speed and efficiency there are several drawbacks all ranging from their lack of ability to execute functions and tasks easily performed by humans. This is mainly due to their lack of ability to implement touch and haptic feedback. In this work, we show the use and applicability of ultra-thin graphene foam (GRF), with polydimethylsiloxane (PDMS) embedded into and over the structure, as an active layer in piezoresistive based pressure sensors for use in robotic touch sensing applications. It has been demonstrated in this work that thin GRF/PDMS-GRF consisting of a few layers of graphene is able to present sensitivity to pressures within the range of 0 to >100kPa. Although pressure sensitivities are not yet comparable to those of current work, it must be noted that the GRF used in this work is much thinner in comparison, consisting of only several layers of graphene.

Abstract: Dielectric elastomer actuator (DEA) is a compact device that consists of stretchable electrodes and elastomers. This device is energy efficient in performance and holds great promise in the development of soft actuators. DEAs performance relies significantly on the mechanical properties of its elastomers. This present study focuses on evaluating the soft material made of Sylgard 184 as the elastomers for DEAs. Sylgard 184 is a silicone elastomer that comes with two main parts (elastomers and its curing agent). A specific mixing ratio between elastomers and curing agent is essential to produce solid and reliable silicone elastomer. The recommended ratio for the elastomer solution was ten parts for the elastomers and one part for the curing agent (10:1). Producing softer elastomers was possible by reducing the curing agent. However, the performance of the material was unknown. We performed a series of cyclic tensile tests to understand the mechanical characteristic of the elastomer made of Sylgard 184. The result shows that reducing the curing agent did not have a significant effect on its cyclic performance. Furthermore, the use of a 30:1 ratio in the application of DEAs and deformable linear actuator indicates stable performance for both devices.

Abstract: A wide range of membranes (hydrophobic and hydrophilic) for the task of triethylene glycol dehydration by thermopervaporation was studied. The transport characteristics of the membranes using individual liquids (water, triethylene glycol) were determined in the thermopervaporation process with varying temperature of the feed flux (40-). The maximum water flux (3.7 kg/m²∙h) in all the studied temperature ranges was demonstrated by the commercial pervaporation hydrophobic PolyAn membrane. For the commercial hydrophilic membrane MDK-I water flux at 80 °С was 2.8 kg/m²∙h. During thermopervaporation of triethylene glycol in the studied temperature range, TEG flux through the membranes was not observed, which shows the advantage of this process for TEG dehydration. For the first time, experiments were provided using PolyAn membranes to removal water from TEG by thermopervaporation with porous condenser. The maximum permeate flux (1.9 kg/m²∙h) was achieved for the PolyAn membrane at a concentration of 70 % wt. TEG in water

Abstract: Dielectric elastomer (DE) technology are used in several applications for example generator, sensor and actuator. One of the major factors that limits the DE performance is premature electrical breakdown. Compositing is the example that have been reported to increase the breakdown strength. In this study polydimethylsiloxane (PDMS) film will be incorporated with two different fillers which are titanium dioxide (TiO₂) and zinc oxide (ZnO). Both metal oxides will be calcined up to 300°C before they are added to the PDMS elastomer as fillers. The results show that the calcined TiO₂ and ZnO that incorporated in PDMS films show significant increase of breakdown strengths. Meanwhile, the calcined TiO₂ PDMS film give higher breakdown strength as comparison to the calcined ZnO counterpart.

Abstract: This paper describes the characterization of conductive PDMS (CPDMS) composites. Composite have been achieved by filling the PDMS with CarbonBlack (CB). Two different methods were used to prepare the CPDMS composites: (A) direct mixing of CB with PDMS (CB-PDMS); (B) dissolving of CB in methanol before mixing with PDMS (CB-Methanol-PDMS). At a certain critical CB concentration, called percolation threshold, the membranes get conductive. Membranes of CPDMS (thickness ≈ 100µm) have been fabricated. CPDMS membranes of method (B) show a smoother surface profile as membranes of method (A). By means of a two–point resistivity measurement, the electrical resistance of CPDMS membranes was measured. With an increase of the CB concentration, the resistance decreases. Membranes of method (B) show a low percolation threshold and a low surface resistivity. Effects of pressure and temperature on the membrane resistance were investigated, too. Around the percolation threshold, the resistance shows the highest sensitivity on pressure and temperature variations. The Young’s modulus of CPDMS membranes exponentially increase with an increase of the CB concentration.

Abstract: In this paper, graphene nanosuspension was spray deposited using electrohydrodynamic atomization (EHDA) technique, and the polydimethylsiloxane (PDMS) was used as the substrate during the EHDA process. The effect of the PDMS substrate before and after oxygen plasma treatment on the characteristics of EHDA was examined. A cone-jet mode of the EHDA of graphene nanosuspension was obtained using the oxygen plasma treated PDMS substrate. In addition graphene films were deposited on the oxygen plasma treated PDMS at different working distances. The lowest sheet resistance of the graphene films is 127Ω·sq^-1. Furthermore, graphene lines at the range of 30μm-170μm were fabricated using the template assisted EHDA deposition method.

Abstract: A novel micropump is proposed comprising a PMMA-based rotor, a circular PDMS micro-chamber, and a semi-circular PDMS microchannel connecting the inlet and outlet reservoirs as the rotor spins, a plug of sample fluid is trapped within the microchannel between neighboring blades of the rotor and is driven through the channel toward the outlet. Meanwhile, the rotors periodically compress and release the inlet and outlet regions of the microchannel. Thus, as the rotor turns, one plug of sample fluid is drawn into the microchannel as another is ejected into the outlet reservoir. In other words, a peristaltic pumping effect is achieved. It is shown that the flow rate in the proposed device can be controlled simply by adjusting the rotational velocity of the rotor. A maximum flow rate of 1.22 ml/min is obtained given de-ionized water as the working fluid and a rotational velocity of 232 rpm. Moreover, given the same rotational velocity, flow rates of 0.724 ml/min and 0.336 ml/min are obtained for salad oil and engine oil, respectively.