Search

Background: Selective photothermolysis (SPT) using a 1726 nm laser has emerged as a safe and effective treatment option for acne vulgaris by targeting sebaceous glands (SG). Power output plays a crucial role in determining treatment selectivity and efficacy. Aims: This work highlights the advantages of a higher‐power laser source and outlines the limitations of lower‐power laser sources and the subsequent impact on treatment. Methods: Light transport and bioheat transfer simulations were performed to demonstrate photothermal impact on the SG and the surrounding dermis when irradiated by a high‐ or lower‐power laser source. Results: The simulations showed that a single higher‐power‐shorter‐pulse (HPSP) selectively increases SG temperature well beyond bulk temperatures, which is desirable for SPT. Selectivity decreases linearly with power for the single lower‐power‐longer‐pulses (LPLP) exposure. A multiple‐LPLP approach elevates bulk temperatures significantly more than a single‐pulse strategy, compromising selectivity. Conclusion: The goal of SPT is to damage SG safely and effectively by creating an intense temperature rise localized to the SG while moderately increasing the dermis temperature. This goal is mostly achieved with higher‐power lasers that deliver a single HPSP. Lower‐power lasers, longer pulse widths, and multi‐pulse strategies result in higher bulk temperatures and lower SG selectivity, making such treatment challenging to execute while adding a higher risk of discomfort and downtime. [ABSTRACT FROM AUTHOR]

A general method is proposed to produce oriented and highly crystalline conducting polymer layers. It combines the controlled orientation/crystallization of polymer films by high-temperature rubbing with a soft-doping method based on spin-coating a solution of dopants in an orthogonal solvent. Doping rubbed films of regioregular poly(3-alkylthiophene)s and poly(2,5-bis(3-dodecylthiophen-2-yl)thieno[3,2- b]thiophene) with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) yields highly oriented conducting polymer films that display polarized UV-visible-near-infrared (NIR) absorption, anisotropy in charge transport, and thermoelectric properties. Transmission electron microscopy and polarized UV-vis-NIR spectroscopy help understand and clarify the structure of the films and the doping mechanism. F4TCNQ− anions are incorporated into the layers of side chains and orient with their long molecular axis perpendicular to the polymer chains. The ordering of dopant molecules depends closely on the length and packing of the alkyl side chains. Increasing the dopant concentration results in a continuous variation of unit cell parameters of the doped phase. The high orientation results in anisotropic charge conductivity (σ) and thermoelectric properties that are both enhanced in the direction of the polymer chains (σ = 22 ± 5 S cm−1 and S = 60 ± 2 µV K−1). The method of fabrication of such highly oriented conducting polymer films is versatile and is applicable to a large palette of semiconducting polymers. [ABSTRACT FROM AUTHOR]

The large majority of semiconducting polymers based on poly(alkylthiophene)s with either linear or branched alkyl side chains are reported to p-stack in their crystalline phases. In regioregular poly(3-(2,5-dioctylphenyl)thiophene) (PDOPT), however, p-p interactions are absent due to the presence of the bulky 2,5-dioctylphenyl side groups. In this work, high levels of crystallinity and orientation are created in thin films of PDOPT aligned on substrates of naphthalene by slow directional epitaxial crystallization of the side chains. Depending on molecular weight, both edge-on and flat-on lamellar crystals are obtained. As for poly(3-hexylthiophene) (P3HT), electron microscopy imaging reveals a transition from extended to folded chain crystallization in PDOPT for Mn ~12.7 kDa. The high orientation and crystallinity result in high anisotropy in UV-vis absorption and photoluminescence with well-defined vibronic structures. The single-crystal-like electron diffraction patterns are further used to refine a structural model of PDOPT (a = 29.09 Å, b = 10.45 Å, c = 7.72 Å, a = ß = γ = 90°, and space group P21/c). Uniquely, crystalline PDOPT features perfectly planarized chains despite the absence of p-stacking between polythiophene backbones. The octyl side chains are interdigitated and crystallize in a dense subcell which is compared to that of other semiconducting polythiophenes, e.g. form I poly(3-hexylthiophene) and poly(2,5-bis(3-dodecyl-2-yl)thieno[3,2-b]thiophene), to draw a trend between overall crystallinity and density of the side chain packing. [ABSTRACT FROM AUTHOR]

Precise control of orientation and crystallinity is achieved in regioregular poly(3-hexylthiophene) (P3HT) thin films by using high-temperature rubbing, a fast and effective alignment method. Rubbing P3HT films at temperatures TR ≥ 144 °C generates highly oriented crystalline films with a periodic lamellar morphology with a dichroic ratio reaching 25. The crystallinity and the average crystal size along the chain axis direction, lc, are determined by high-resolution transmission electron microscopy and differential scanning calorimetry. The inverse of the lamellar period l scales with the supercooling and can accordingly be controlled by the rubbing temperature TR. Uniquely, the observed exciton coupling in P3HT crystals is correlated to the length of the average planarized chain segments lc in the crystals. The high alignment and crystallinity observed for TR > 200 °C cannot translate to high hole mobilities parallel to the rubbing because of the adverse effect of amorphous zones interrupting charge transport between crystalline lamellae. Although tie chains bridge successive P3HT crystals through amorphous zones, their twisted conformation restrains interlamellar charge transport. The evolution of charge transport anisotropy is correlated to the evolution of the dominant contact plane from mainly face-on ( TR ≤ 100 °C) to edge-on ( TR ≥ 170 °C). [ABSTRACT FROM AUTHOR]

In this article we highlight the importance of film deposition conditions on the electrochemical behaviour of the work horse of the organic electronics community, namely poly(3-hexylthiophene) (P3HT). While a huge number of publications have dealt with the influence of morphology on optical, electronic and opto-electronic properties, the effect on the electrochemical response has been less addressed. Electrochemistry is often only used as convenient tool in this community to determine the energy levels or more specifically the HOMO level of P3HT. This is performed by measuring oxidation onset potentials and introducing correction factors which relate the electrochemical with the Fermi scale. Here we want to stress out that this procedure should be performed with great care in order to get meaningful data. We demonstrate that film deposition conditions can strongly alter the oxidation behaviour of the polymers which makes the determination of the oxidation onset potentials and energy levels very difficult. We compare state-of-the-art of electropolymerisation and solution deposition of chemically synthesized polymers of defined regioregularity with our own expertise on deposition and controlling crystallisation in films. [ABSTRACT FROM AUTHOR]

Background: Selective photothermolysis on sebaceous glands is an effective method for treating acne vulgaris (AV); however, safety, efficacy, and discomfort hinder its utilization in clinical settings. Aims: The primary objective is to evaluate the safety and efficacy of a novel 1726 nm laser with contact cooling to treat AV. Methods: Seventeen patients aged 18 to 36 were enrolled and treated in this IRB‐approved, single‐center, open‐label study. Patients received up to three facial laser sessions up to seven weeks apart. Follow‐up visits happened ten days post‐session and at the 4 and 12 weeks following the final session. The investigator assessed the severity of device‐related adverse events (AEs). Investigator Global Assessment (IGA) and inflammatory lesion counts (ILC) were used as metrics to evaluate acne resolution and skin condition enhancement. Patients' perspectives on satisfaction and comfort using this technology were assessed using Subject Experience Questionnaires (SEQ). Results: Safety assessment showed mild and transient AEs. All subjects tolerated anesthetics‐free treatments well, with a mean treatment discomfort score of 4.9 ± 1.5. Compared to baseline, a statistically significant reduction in ILC (p = 0.003) of 52% to 56% is achieved four to twelve weeks following treatment. Long‐term follow‐ups showed progressive improvement 24 months post‐treatment with a 97% reduction in ILC. SEQs revealed high subject satisfaction (71%) with psychosocial improvement three months post‐treatment. Conclusion: The novel 1726 nm laser appears safe and effective for treating mild‐to‐severe acne. Acne resolution is apparent within the first month and progresses beyond the study duration. [ABSTRACT FROM AUTHOR]

Organic electrochemical transistors (OECTs) are the building blocks of biosensors, neuromorphic devices, and complementary circuits. One rule in the materials design for OECTs is the inclusion of a hydrophilic component in the chemical structure to enable ion transport in the film. Here, it is shown that the ladder‐type, side‐chain free polymer poly(benzimidazobenzophenanthroline) (BBL) performs significantly better in OECTs than the donor–acceptor type copolymer bearing hydrophilic ethylene glycol side chains (P‐90). A combination of electrochemical techniques reveals that BBL exhibits a more efficient ion‐to‐electron coupling and higher OECT mobility than P‐90. In situ atomic force microscopy scans evidence that BBL, which swells negligibly in electrolytes, undergoes a drastic and permanent change in morphology upon electrochemical doping. In contrast, P‐90 substantially swells when immersed in electrolytes and shows moderate morphology changes induced by dopant ions. Ex situ grazing incidence wide‐angle X‐ray scattering suggests that the particular packing of BBL crystallites is minimally affected after doping, in contrast to P‐90. BBL's ability to show exceptional mixed transport is due to the crystallites' connectivity, which resists water uptake. This side chain‐free route for the design of mixed conductors could bring the n‐type OECT performance closer to the bar set by their p‐type counterparts. [ABSTRACT FROM AUTHOR]