Friction Transfer of Teflon to Template the Growth of Organic Semiconductors

Organic field effect transistors (OFET) based on the latest generation of p-type organic semiconductors (DNTTT, C10-DNTT) display excellent characteristics, with charge transport mobility of up to 10 cm2/Vs. These materials reach the quality levels of n-type oxide semiconductors (IGZO), potentially enabling the development of a complementary technology (CMOS) for low-cost electronic circuits on large area flexible foils. Examples of potential applications for such circuits are RFID tags, smart packaging, flexible displays and numerous biomedical applications. Among other things, the performance of OFET depends on the degree of crystallinity of the organic semiconductors. Higher ordering delivers better performance, and, the best OFETs are based on defect free single organic crystals. The production of thin films of defect free organic single crystals over large area is therefore highly desirable. This, however, remains a considerable challenge since the presence of only a few defects will negatively impact the spread of TFT characteristics. As the spread increases, the yield of circuits dramatically decreases. Templating that relies on a good match between the crystal structures of the substrate and the grown material is very well known in the field of epitaxial growth of inorganic materials. In the field of organic electronics, however, much remains to be done. Therefore we aim to develop a method to transfer a thin, uniform and aligned film of Polytetrafluoroethylene (PTFE) on the substrate as a template to grow organic semiconductors and increasing their degree of order following by making OFET. The influence of the PTFE layer on the performance of OFET is studied

Friction Transfer of Teflon to Template the Growth of Organic Semiconductors

Organic field effect transistors (OFET) based on the latest generation of p-type organic semiconductors (DNTTT, C10-DNTT) display excellent characteristics, with charge transport mobility of up to 10 cm2/Vs. These materials reach the quality levels of n-type oxide semiconductors (IGZO), potentially enabling the development of a complementary technology (CMOS) for low-cost electronic circuits on large area flexible foils. Examples of potential applications for such circuits are RFID tags, smart packaging, flexible displays and numerous biomedical applications. Among other things, the performance of OFET depends on the degree of crystallinity of the organic semiconductors. Higher ordering delivers better performance, and, the best OFETs are based on defect free single organic crystals. The production of thin films of defect free organic single crystals over large area is therefore highly desirable. This, however, remains a considerable challenge since the presence of only a few defects will negatively impact the spread of TFT characteristics. As the spread increases, the yield of circuits dramatically decreases. Templating that relies on a good match between the crystal structures of the substrate and the grown material is very well known in the field of epitaxial growth of inorganic materials. In the field of organic electronics, however, much remains to be done. Therefore we aim to develop a method to transfer a thin, uniform and aligned film of Polytetrafluoroethylene (PTFE) on the substrate as a template to grow organic semiconductors and increasing their degree of order following by making OFET. The influence of the PTFE layer on the performance of OFET is studied

The Effect of Encapsulation Geometry on the Performance of Stretchable Interconnects

The stretchability of electronic devices is typically obtained by tailoring the stretchable interconnects that link the functional units together. The durability of the interconnects against environmental conditions, such as deformation and chemicals, is therefore important to take into account. Different approaches, including encapsulation, are commonly used to improve the endurance of stretchable interconnects. In this paper, the geometry of encapsulation layer is initially investigated using finite element analysis. Then, the stretchable interconnects with a narrow-to-wide layout are screen-printed using silver flake ink as a conductor on a thermoplastic polyurethane (TPU) substrate. Printed ultraviolet (UV)-curable screen-printed dielectric ink and heat-laminated TPU film are used for the encapsulation of the samples. The electromechanical tests reveal a noticeable improvement in performance of encapsulated samples compared to non-protected counterparts in the case of TPU encapsulation. The improvement is even greater with partial coverage of the encapsulation layer. A device with a modified encapsulation layer can survive for 10,000 repetitive cycles at 20% strain, while maintaining the electrical and mechanical performance

Screen-printed curvature sensors for soft robots

Castable elastomers have been used to fabricate soft robotic devices and it has been shown that the technique scales well from prototyping to mass manufacturing. However, similarly scalable techniques for integrating strain or curvature sensors into such devices are still lacking. In this paper, we show that screenprinted silver conductors serve well as curvature sensors for soft robotic devices. The sensors are produced onto elastomer substrates in a single printing step and integrated into soft pneumatic actuators. We characterized the resistance-curvature relationship of the sensors, which allows the curvature of the actuators to be estimated from the sensor measurements. Hysteresis was observed, which does limit the absolute accuracy of the sensors. However, temperature characterizations showed that the sensor measurements are not significantly affected by temperature fluctuations during normal operation. Dynamic experiments showed that the bandwidth of the sensors is larger than the bandwidth of the actuators. We experimentally validated that these sensors can be used to detect whether the motion of an actuator has been blocked, clearing the way towards simple-tofabricate soft robots that react to their surroundings. Finally, we demonstrate a three-fingered soft robotic gripper with integrated sensors. We conclude that screen-printing is a promising way to integrate curvature sensors into soft robots.acceptedVersionPeer reviewe

The efficacy of Isotretinoin-loaded solid lipid nanoparticles in comparison to Isotrex® on acne treatment

Abstract: Topical retinoids are considered as the first line therapy in the treatment of acne vulgaris, but they are associated with cutaneous irritation. In this study, isotretinoin-loaded solid lipid nanoparticles(IT-SLN) were prepared to treat the mild to moderate acne. Also using IT-SLN would minimize IT adverse effects in comparison to commercial product, Isotrex®. This study was conducted to prepare and characterize IT-SLN and assessing the efficiency of IT-SLN comparing to Isotrex® acne. IT-SLN was prepared using hot high pressure homogenization method.  IT-SLN contained 0.05% IT in 5% of lipid phase (Glyceryl monostearate- GMS) and tween 80 (2.5 % w/v) was used as surfactant in the aqueous phase. IT-SLN was characterized by particle size analyzing, differential scanning calorimetry and transmission electron microscopy. Encapsulation efficacy was also obtained using spectrophotometry. The efficacy of IT-SLN was evaluated in a randomized, single-blind, parallel-group study and compared with Isotrex®. Forty patients encountered in the study and divided in two groups. Treatment regimen was once-nightly topical administration accompanied with topical administration of clindamycin 2% solution twice a day for 8 weeks. The particle size of IT-SLN was around 60 nm with PDI of 0.4 and zeta potential was about -40 mV. Encapsulation efficacy of IT in SLN in crystalline form was 84±0.21%. IT-SLN produced significantly better treatment than Isotrex® in both non-inflammatory and inflammatory lesions according to its recovery percent after 8 weeks. Also IT-SLN gained better global assessment scores. Our results showed that IT-SLN had higher efficacy than Isotrex® to clear non-inflammatory and inflammatory lesions

Screen-Printing Fabrication and Characterization of Stretchable Electronics

This article focuses on the fabrication and characterization of stretchable interconnects for wearable electronics applications. Interconnects were screen-printed with a stretchable silver-polymer composite ink on 50-μm thick thermoplastic polyurethane. The initial sheet resistances of the manufactured interconnects were an average of 36.2 mω and half the manufactured samples withstood single strains of up to 74%. The strain proportionality of resistance is discussed, and a regression model is introduced. Cycling strain increased resistance. However, the resistances here were almost fully reversible, and this recovery was time-dependent. Normalized resistances to 10%, 15%, and 20% cyclic strains stabilized at 1.3, 1.4, and 1.7. We also tested the validity of our model for radio-frequency applications through characterization of a stretchable radio-frequency identification tag.publishedVersionpublishedVersionPeer reviewe