The Latin Leaflet, Number 29

Polymer electrolytes represent the ultimate in terms of desirable properties of energy storage/conversion devices, as they can offer an all-solid-state construction, a wide variety of shapes and sizes, light-weight, low costs, high energy density and safety. Here we present our recent results concerning a novel strategy for preparing efficient polymer membranes which are successfully demonstrated as suitable electrolytes for several energy conversion and storage devices (i.e., Li- and Na-based batteries and DSSCs). Highly ionic conducting polymer electrolytes containing PEO-based functionalities and different components (e.g., Li/Na salts, RTILs, natural biosourced and cellulosic fillers) are successfully prepared via a rapid process and, directly or subsequently, cross-linked via UV irradiation (patent pending, PCT/IT2014/000008). All the prepared materials are thoroughly characterised in terms of their physical, chemical and morphological properties and tested for their electrochemical performances and durability. The UV-curing process on such materials led to the production of elastic and resistant amorphous macromolecular networks. Noticeably increased ionic conductivities are registered (10-3 S cm-1 at RT), along with very stable interfacial and storage stability and wide electrochemical stability windows. The different lab-scale solid-state devices show remarkable performances even at ambient temperature, at the level of those using liquid electrolytes, respect to which demonstrate much greater durability and safety. The obtained findings demonstrate a new, easy and low cost approach to fabricate and tailor-make polymer electrolytes with highly promising prospects for the next generation of advanced flexible energy production and storage devices

A Na+ conducting hydrogel for protection of organic electrochemical transistors.

Organic electrochemical transistors (OECTs) are being intensively developed for applications in electronics and biological interfacing. These devices rely on ions injected in a polymer film from an aqueous liquid electrolyte for their operation. However, the development of solid or semi-solid electrolytes are needed for future integration of OECTs into flexible, printed or conformable bioelectronic devices. Here, we present a new polyethylene glycol hydrogel with high Na+ conductivity which is particularly suitable for OECTs. This novel hydrogel was synthesized using cost-effective photopolymerization of poly(ethylene glycol)-dimethacrylate and sodium acrylate. Due to the high water content (83% w/w) and the presence of free Na+, the hydrogel showed high ionic conductivity values at room temperature (10-2 S cm-1) as characterized by electrochemical impedance spectroscopy. OECTs made using this hydrogel as a source of ions showed performance that was equivalent to that of OECTs employing a liquid electrolyte. They also showed improved stability, with only a 3% drop in current after 6 h of operation. This hydrogel paves the way for the replacement of liquid electrolytes in high performance OECTs bringing about advantages in terms of device integration and protection

Ionic Hydrogel for Accelerated Dopamine Delivery via Retrodialysis.

Local drug delivery directly to the source of a given pathology using retrodialysis is a promising approach to treating otherwise untreatable diseases. As the primary material component in retrodialysis, the semipermeable membrane represents a critical point for innovation. This work presents a new ionic hydrogel based on polyethylene glycol and acrylate with dopamine counterions. The ionic hydrogel membrane is shown to be a promising material for controlled diffusive delivery of dopamine. The ionic nature of the membrane accelerates uptake of cationic species compared to a nonionic membrane of otherwise similar composition. It is demonstrated that the increased uptake of cations can be exploited to confer an accelerated transport of cationic species between reservoirs as is desired in retrodialysis applications. This effect is shown to enable nearly 10-fold increases in drug delivery rates from low concentration solutions. The processability of the membrane is found to allow for integration with microfabricated devices which will in turn accelerate adaptation into both existing and emerging device modalities. It is anticipated that a similar materials design approach may be broadly applied to a variety of cationic and anionic compounds for drug delivery applications ranging from neurological disorders to cancer

Diagnostic Role of Bronchoalveolar Lavage in Patients with Suspected SARS-CoV-2 Pneumonia and Negative Upper Respiratory Tract Swab: A Systematic Review and Meta-Analysis

The added role of bronchoalveolar lavage (BAL) in SARS-CoV-2 detection in hospitalized patients with suspected COVID-19 pneumonia and at least one negative nasopharyngeal swab (NPS) has yet to be definitively established. We aimed to provide a systematic review and meta-analysis to summarize data from the literature on the diagnostic yield of BAL in this context. We searched Medline and Embase for all studies reporting outcomes of interest published up to October 2021. Two authors reviewed all titles/abstracts and retrieved the selected full texts according to predefined selection criteria. The summary estimate was derived using the random-effects model. Thirteen original studies, involving 868 patients, were included. The summary estimate of proportions of SARS-CoV-2 positivity in BAL fluid in patients with at least one previous negative NPS was 20% (95% confidence interval [CI]; 11–30%). Moreover, microbiological tests of BAL fluid led to the identification of other pathogens, mainly bacteria, in up to two-thirds of cases. BAL plays a crucial role in the diagnostic work-up of patients with clinical suspicion of COVID-19 and previous negative NPS, as it allowed to detect the infection in a significant proportion of subjects, who would have been otherwise misclassified, with relevant implications in the prevention of disease spread, especially in hospital settings

Tuning the properties of a UV-polymerized, cross-linked solid polymer electrolyte for lithium batteries

Lithium metal anodes have been pursued for decades as a way to significantly increase the energy density of lithium-ion batteries. However, safety risks caused by flammable liquid electrolytes and short circuits due to lithium dendrite formation during cell cycling have so far prevented the use of lithium metal in commercial batteries. Solid polymer electrolytes (SPEs) offer a potential solution if their mechanical properties and ionic conductivity can be simultaneously engineered. Here, we introduce a family of SPEs that are scalable and easy to prepare with a photopolymerization process, synthesized from amphiphilic acrylic polymer conetworks based on poly(ethylene glycol), 2-hydroxy-ethylacrylate, norbornyl acrylate, and either lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) or a single-ion polymethacrylate as lithium-ion source. Several conetworks were synthesized and cycled, and their ionic conductivity, mechanical properties, and lithium transference number were characterized. A single-ion-conducting polymer electrolyte shows the best compromise between the different properties and extends the calendar life of the cell

Task-Specific Phosphonium Iongels by Fast UV-Photopolymerization for Solid-State Sodium Metal Batteries

Sodium metal batteries are an emerging technology that shows promise in terms of materials availability with respect to lithium batteries. Solid electrolytes are needed to tackle the safety issues related to sodium metal. In this work, a simple method to prepare a mechanically robust and efficient soft solid electrolyte for sodium batteries is demonstrated. A task-specific iongel electrolyte was prepared by combining in a simple process the excellent performance of sodium metal electrodes of an ionic liquid electrolyte and the mechanical properties of polymers. The iongel was synthesized by fast (<1 min) UV photopolymerization of poly(ethylene glycol) diacrylate (PEGDA) in the presence of a saturated 42%mol solution of sodium bis(fluorosulfonyl)imide (NaFSI) in trimethyl iso-butyl phosphonium bis(fluorosulfonyl)imide (P111i4FSI). The resulting soft solid electrolytes showed high ionic conductivity at room temperature (≥10−3 S cm−1) and tunable storage modulus (104–107 Pa). Iongel with the best ionic conductivity and good mechanical properties (Iongel10) showed excellent battery performance: Na/iongel/NaFePO4 full cells delivered a high specific capacity of 140 mAh g−1 at 0.1 C and 120 mAh g−1 at 1 C with good capacity retention after 30 cycles.L.P. has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska–Curie grant agreement No. 797295. P.S. has been funded by the SNSF (Swiss National Science Foundation) under project number P2FRP2_191846. D.M., M.G., and A.F.A. acknowledge the funding by the Basque Government through Elkartek KK-2020/00078 and Agencia Estatal de Investigación (PLEC2021-007929). D.M. and M.G. also acknowledge the funding by Agencia Estatal de Investigación (PID2020-119026GB-100 and PID2019-107468RB-C22), respectively. A.P.S. acknowledges financial support for dielectric measurements and data discussions by NSF (award CHE-2102425)

Characterization of lithium-ion capacitors for low-power energy neutral wireless sensor networks

Sensor nodes in wireless sensor networks (WSNs) are often powered by energy harvesting devices used to extend the lifetime of the nodes and energy storage elements are fundamental to collect the exceeding power incoming from the ambient. The stored energy is then consumed to supply the sensor node when the ambient energy is scarce or insufficient to satisfy the current requests from the load. To date, the choice of the storage element is made between rechargeable batteries and electric double-layer capacitors (EDLC or supercapacitors), and many works in literature exploit hybrid storage architectures. In this paper we characterize an innovative technology available on the market, namely the lithium-ion capacitor (LIC). We show that this cutting edge technology combines the high cell voltage, the energy density and the low self-discharge of a lithium battery with the power density, the high capacity and long cycle life of a supercapacitor

High performance photolithographically-patterned polymer thin-film transistors gated with an ionic liquid/poly(ionic liquid) blend ion gel

We demonstrate the fabrication of polymer thin-film transistors gated with an ion gel electrolyte made of the blend of an ionic liquid and a polymerised ionic liquid. The ion gel exhibits a high stability and ionic conductivity, combined with facile processing by simple drop-casting from solution. In order to avoid parasitic effects such as high hysteresis, high off-currents, and slow switching, a fluorinated photoresist is employed in order to enable high-resolution orthogonal patterning of the polymer semiconductor over an area that precisely defines the transistor channel. The resulting devices exhibit excellent characteristics, with an on/off ratio of 106, low hysteresis, and a very large transconductance of 3 mS. We show that this high transconductance value is mostly the result of ions penetrating the polymer film and doping the entire volume of the semiconductor, yielding an effective capacitance per unit area of about 200 μF cm−2, one order of magnitude higher than the double layer capacitance of the ion gel. This results in channel currents larger than 1 mA at an applied gate bias of only –1 V. We also investigate the dynamic performance of the devices and obtain a switching time of 20 ms, which is mostly limited by the overlap capacitance between the ion gel and the source and drain contacts