Linköping University

About: Linköping University is a education organization based out in Linköping, Sweden. It is known for research contribution in the topics: Population & Thin film. The organization has 15671 authors who have published 50013 publications receiving 1542189 citations.

Knitting and weaving artificial muscles.

Abstract: A need exists for artificial muscles that are silent, soft, and compliant, with performance characteristics similar to those of skeletal muscle, enabling natural interaction of assistive devices with humans. By combining one of humankind’s oldest technologies, textile processing, with electroactive polymers, we demonstrate here the feasibility of wearable, soft artificial muscles made by weaving and knitting, with tunable force and strain. These textile actuators were produced from cellulose yarns assembled into fabrics and coated with conducting polymers using a metal-free deposition. To increase the output force, we assembled yarns in parallel by weaving. The force scaled linearly with the number of yarns in the woven fabric. To amplify the strain, we knitted a stretchable fabric, exhibiting a 53-fold increase in strain. In addition, the textile construction added mechanical stability to the actuators. Textile processing permits scalable and rational production of wearable artificial muscles, and enables novel ways to design assistive devices.

Oriented Quasi-2D Perovskites for High Performance Optoelectronic Devices

Abstract: Quasi-2D layered organometal halide perovskites have recently emerged as promising candidates for solar cells, because of their intrinsic stability compared to 3D analogs. However, relatively low power conversion efficiency (PCE) limits the application of 2D layered perovskites in photovoltaics, due to large energy band gap, high exciton binding energy, and poor interlayer charge transport. Here, efficient and water-stable quasi-2D perovskite solar cells with a peak PCE of 18.20% by using 3-bromobenzylammonium iodide are demonstrated. The unencapsulated devices sustain over 82% of their initial efficiency after 2400 h under relative humidity of ≈40%, and show almost unchanged photovoltaic parameters after immersion into water for 60 s. The robust performance of perovskite solar cells results from the quasi-2D perovskite films with hydrophobic nature and a high degree of electronic order and high crystallinity, which consists of both ordered large-bandgap perovskites with the vertical growth in the bottom region and oriented small-bandgap components in the top region. Moreover, due to the suppressed nonradiative recombination, the unencapsulated photovoltaic devices can work well as light-emitting diodes (LEDs), exhibiting an external quantum efficiency of 3.85% and a long operational lifetime of ≈96 h at a high current density of 200 mA cm-2 in air.

Enhancing the photovoltage of polymer solar cells by using a modified cathode

Abstract: A method to increase the open-circuit voltage (Voc) up to 200 mV and the power conversion efficiency (PCE) by 50%, by using a thin layer of poly(ethylene oxide) (PEO) to modify the cathode in polymer solar cells, was reported. An enhanced photocurrent of polymer solar cells by bending a small amount of PEO and LiCF3SO3 into the active layer was also demonstrated. The results show that the value of open-circuit voltage increases in all diodes with PEO by 150 to 200 mV while the fill factor (FF) increases with a decrease of the thickness of PEO. The thickness of the PEO layers on Si wafers measured by using ellipsometry shows that the thickness are 3.8 nm for 1000 rmp, 2.1 nm for 3000 rmp, and 1.4 nm for 5000 rmp. The quantitative similarity of the J-V characteristics in the dark between the diodes containing PEO and LiF shows that PEO has an analogous function in the device as LiF.

Channel Hardening and Favorable Propagation in Cell-Free Massive MIMO With Stochastic Geometry

Abstract: Cell-free (CF) massive multiple-input multiple-output (MIMO) is an alternative topology for future wireless networks, where a large number of single-antenna access points (APs) are distributed over the coverage area. There are no cells but all users are jointly served by the APs using network MIMO methods. Prior works have claimed that the CF massive MIMO inherits the basic properties of cellular massive MIMO, namely, channel hardening and favorable propagation. In this paper, we evaluate if one can rely on these properties when having a realistic stochastic AP deployment. Our results show that channel hardening only appears in special cases, for example, when the pathloss exponent is small. However, by using 5–10 antennas per AP, instead of one, we can substantially improve the hardening. Only spatially well-separated users will exhibit favorable propagation, but when adding more antennas and/or reducing the pathloss exponent, it becomes more likely for favorable propagation to occur. The conclusion is that we cannot rely on the channel hardening and the favorable propagation when analyzing and designing the CF massive MIMO networks, but we need to use achievable rate expressions and resource allocation schemes that work well also in the absence of these properties. Some options are reviewed in this paper.

Anti-tumour necrosis factor therapy in rheumatoid arthritis and risk of malignant lymphomas: relative risks and time trends in the Swedish Biologics Register

Abstract: Background: Tumour necrosis factor (TNF) antagonists have proved effective as treatment against rheumatoid arthritis ( RA), but the unresolved issue of whether the use of anti-TNF therapy increases the already elevated risk of lymphoma in RA remains a concern. Methods: Using the Swedish Biologics Register (ARTIS), the Swedish Cancer Register, pre-existing RA cohorts and cross-linkage with other national health and census registers, a national RA cohort (n = 67 743) was assembled and patients who started anti-TNF therapy between 1998 and July 2006 ( n = 6604) were identified. A general population comparator ( n = 471 024) was also assembled and the incidence of lymphomas from 1999 to 31 December 2006 was assessed and compared in these individuals. Results: Among the 6604 anti-TNF-treated RA patients, 26 malignant lymphomas were observed during 26 981 person-years of follow-up, which corresponded to a relative risk (RR) of 1.35 (95% CI 0.82 to 2.11) versus anti-TNF-naive RA patients ( 336 lymphomas during 365 026 person-years) and 2.72 ( 95% CI 1.82 to 4.08) versus the general population comparator ( 1568 lymphomas during 3 355 849 person-years). RA patients starting anti-TNF therapy in 1998-2001 accounted for the entire increase in lymphoma risk versus the two comparators. By contrast, RR did not vary significantly by time since start of first treatment or with the accumulated duration of treatment, nor with the type of anti-TNF agent. Conclusion: Overall and as used in routine care against RA, TNF antagonists are not associated with any major further increase in the already elevated lymphoma occurrence in RA. Changes in the selection of patients for treatment may influence the observed risk.