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The solution processing of polycrystalline perovskite films introduces trap states that can adversely affect their optoelectronic properties. Motivated by the use of small-molecule surfactants to improve the optoelectronic performance of perovskites, we demonstrate the use of polymers with coordinating groups to improve the performance of solution-processed semiconductor films. The use of these polymer modifiers results in a marked change in the electronic properties of the films, as measured by both carrier dynamics and overall device performance. The devices grown with the polymer poly(4-vinylpyridine) (PVP) show significantly enhanced power conversion efficiency from 16.9 ± 0.7% to 18.8 ± 0.8% (champion efficiency, 20.2%) from a reverse scan and stabilized champion efficiency from 17.5 to 19.1% [under a bias of 0.94 V and AM (air mass) 1.5-G, 1-sun illumination over 30 min] compared to controls without any passivation. Treating the perovskite film with PVP enables a VOC of up to 1.16 V, which is among the best reported for a CH3NH3PbI3 perovskite solar cell and one of the lowest voltage deficits reported for any perovskite to date. In addition, perovskite solar cells treated with PVP show a long shelf lifetime of up to 90 days (retaining 85% of the initial efficiency) and increased by a factor of more than 20 compared to those without any polymer (degrading to 85% after ~4 days). Our work opens up a new class of chemical additives for improving perovskite performance and should pave the way toward improving perovskite solar cells for high efficiency and stability.

Background Commercially available near infrared spectroscopy devices for continuous free flap tissue oxygenation (StO 2) monitoring can only be used on flaps with a cutaneous component. Additionally, differences in skin quality and pigmentation may alter StO 2 measurements. Here, we present a novel implantable heat convection probe that measures microvascular blood flow for peripheral monitoring of free flaps, and is not subject to the same issues that limit the clinical utility of near-infrared spectroscopy. Methods The intratissue microvascular flow-sensing device includes a resistive heater, 4 thermistors, a small battery, and a Bluetooth chip, which allows connection to a smart device. Convection of applied heat is measured and mathematically transformed into a measurement of blood flow velocity. This was tested alongside Vioptix T.Ox in a porcine rectus abdominis myocutaneous flap model of arterial and venous occlusion. After flap elevation, the thermal device was deployed intramuscularly, and the cutaneous T.Ox device was applied. Acland clamps were alternately applied to the flap artery and veins to achieve 15 minutes periods of flap ischemia and congestion with a 15 minutes intervening recovery period. In total, five devices were tested in three flaps in three separate pigs over 16 vaso-occlusive events. Results Flow measurements were responsive to both ischemia and congestion, and returned to baseline during recovery periods. Flow measurements corresponded closely with measured StO 2. Cross-correlation at zero lag showed agreement between these two sensing modalities. Two novel devices tested simultaneously on the same flap showed only minor variations in flow measurements. Conclusion This novel probe is capable of detecting changes in tissue microcirculatory blood flow. This device performed well in a swine model of flap ischemia and congestion, and shows promise as a potentially useful clinical tool. Future studies will investigate performance in fasciocutaneous flaps and characterize longevity of the device over a period of several days. [ABSTRACT FROM AUTHOR]

Serial examination and direct measurement of intracompartmental pressure (ICP) are suboptimal strategies for the detection of acute compartment syndrome (CS) because they are operator‐dependent and yield information that only indirectly reflects intracompartmental muscle perfusion. As a result, instances of unnecessary fasciotomy and unrecognized CS are relatively common. Recently, near‐infrared spectroscopy (NIRS)‐based systems for compartment monitoring have generated interest as an adjunct tool. Under ideal conditions, NIRS directly measures the oxygenation of intracompartmental muscle (StO2), thereby obviating the challenges of interpreting equivocal clinical examination or ICP data. Despite these potential advantages, existing NIRS sensors are plagued by technical difficulties that limit clinical utility. Most of these limitations relate to their transcutaneous design that makes them susceptible to both interference from intervening skin/subcutaneous tissue, underlying hematoma, and instability of the skin‐sensor interface. Here, we present a flexible, wireless, Bluetooth‐enabled, percutaneously introducible intramuscular NIRS device that directly and continuously measures the StO2 of intracompartmental muscle. Proof of concept for this device is demonstrated in a swine lower extremity balloon compression model of acute CS, wherein we simultaneously track muscle oxygenation, ICP, and compartment perfusion pressure (PP). The observed StO2 decreased with increasing ICP and decreasing PP and then recovered following pressure reduction. The mean change in StO2 as the PP was decreased from baseline to 30 mmHg was −7.6%. The mean difference between baseline and nadir StO2 was −17.4%. Cross‐correlations (absolute value) describing the correspondence between StO2 and ICP were >0.73. This novel intramuscular NIRS device identifies decreased muscle perfusion in the setting of evolving CS. Statement of Clinical Significance: This novel intramuscular near‐infrared spectroscopy device can directly measure the perfusion of intracompartmental muscle and holds promise as a potential clinical tool to facilitate early and accurate diagnosis of acute compartment syndrome of the limb. [ABSTRACT FROM AUTHOR]

Background  Current near-infrared spectroscopy (NIRS)-based systems for continuous flap monitoring are limited to flaps which carry a cutaneous paddle. As such, this useful and reliable technology has not previously been applicable to muscle-only free flaps where other modalities with substantial limitations continue to be utilized. Methods  We present the first NIRS probe which allows continuous monitoring of local tissue oxygen saturation (StO 2) directly within the substance of muscle tissue. This probe is flexible, subcentimeter in scale, waterproof, biocompatible, and is fitted with resorbable barbs which facilitate temporary autostabilization followed by easy atraumatic removal. This novel device was compared with a ViOptix T.Ox monitor in a porcine rectus abdominus myocutaneous flap model of arterial and venous occlusions. During these experiments, the T.Ox device was affixed to the skin paddle, while the novel probe was within the muscle component of the same flap. Results  The intramuscular NIRS device and skin-mounted ViOptix T.Ox devices produced very similar StO 2 tracings throughout the vascular clamping events, with obvious and parallel changes occurring upon vascular clamping and release. The normalized cross-correlation at zero lag describing correspondence between the novel intramuscular NIRS and T.Ox devices was >0.99. Conclusion  This novel intramuscular NIRS probe offers continuous monitoring of oxygen saturation within muscle flaps. This experiment demonstrates the potential suitability of this intramuscular NIRS probe for the task of muscle-only free flap monitoring, where NIRS has not previously been applicable. Testing in the clinical environment is necessary to assess durability and reliability. [ABSTRACT FROM AUTHOR]

Continuous monitoring of biomarkers at locations adjacent to targeted internal organs can provide actionable information about postoperative status beyond conventional diagnostic methods. As an example, changes in pH in the intra-abdominal space after gastric surgeries can serve as direct indicators of potentially life-threatening leakage events, in contrast to symptomatic reactions that may delay treatment. Here, we report a bioresorbable, wireless, passive sensor that addresses this clinical need, designed to locally monitor pH for early detection of gastric leakage. A pH-responsive hydrogel serves as a transducer that couples to a mechanically optimized inductor-capacitor circuit for wireless readout. This platform enables real-time monitoring of pH with fast response time (within 1 hour) over a clinically relevant period (up to 7 days) and timely detection of simulated gastric leaks in animal models. These concepts have broad potential applications for temporary sensing of relevant biomarkers during critical risk periods following diverse types of surgeries.