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1.
Proc Natl Acad Sci U S A ; 120(39): e2221815120, 2023 09 26.
Artigo em Inglês | MEDLINE | ID: mdl-37722037

RESUMO

Photocurrent in quantum materials is often collected at global contacts far away from the initial photoexcitation. This collection process is highly nonlocal. It involves an intricate spatial pattern of photocurrent flow (streamlines) away from its primary photoexcitation that depends sensitively on the configuration of current collecting contacts as well as the spatial nonuniformity and tensor structure of conductivity. Direct imaging to track photocurrent streamlines is challenging. Here, we demonstrate a microscopy method to image photocurrent streamlines through ultrathin heterostructure devices comprising platinum on yttrium iron garnet (YIG). We accomplish this by combining scanning photovoltage microscopy with a uniform rotating magnetic field. Here, local photocurrent is generated through a photo-Nernst type effect with its direction controlled by the external magnetic field. This enables the mapping of photocurrent streamlines in a variety of geometries that include conventional Hall bar-type devices, but also unconventional wing-shaped devices called electrofoils. In these, we find that photocurrent streamlines display contortion, compression, and expansion behavior depending on the shape and angle of attack of the electrofoil devices, much in the same way as tracers in a wind tunnel map the flow of air around an aerodynamic airfoil. This affords a powerful tool to visualize and characterize charge flow in optoelectronic devices.

2.
Proc Natl Acad Sci U S A ; 120(35): e2306272120, 2023 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-37603750

RESUMO

Semiconducting conjugated polymers bearing glycol side chains can simultaneously transport both electronic and ionic charges with high charge mobilities, making them ideal electrode materials for a range of bioelectronic devices. However, heavily glycolated conjugated polymer films have been observed to swell irreversibly when subjected to an electrochemical bias in an aqueous electrolyte. The excessive swelling can lead to the degradation of their microstructure, and subsequently reduced device performance. An effective strategy to control polymer film swelling is to copolymerize glycolated repeat units with a fraction of monomers bearing alkyl side chains, although the microscopic mechanism that constrains swelling is unknown. Here we investigate, experimentally and computationally, a series of archetypal mixed transporting copolymers with varying ratios of glycolated and alkylated repeat units. Experimentally we observe that exchanging 10% of the glycol side chains for alkyl leads to significantly reduced film swelling and an increase in electrochemical stability. Through molecular dynamics simulation of the amorphous phase of the materials, we observe the formation of polymer networks mediated by alkyl side-chain interactions. When in the presence of water, the network becomes increasingly connected, counteracting the volumetric expansion of the polymer film.

3.
Proc Natl Acad Sci U S A ; 120(24): e2304506120, 2023 Jun 13.
Artigo em Inglês | MEDLINE | ID: mdl-37279276

RESUMO

Dynamic molecular devices operating with time- and history-dependent performance raised new challenges for the fundamental study of microscopic non-steady-state charge transport as well as functionalities that are not achievable by steady-state devices. In this study, we reported a generic dynamic mode of molecular devices by addressing the transient redox state of ubiquitous quinone molecules in the junction by proton/water transfer. The diffusion limited slow proton/water transfer-modulated fast electron transport, leading to a non-steady-state transport process, as manifested by the negative differential resistance, dynamic hysteresis, and memory-like behavior. A quantitative paradigm for the study of the non-steady-state charge transport kinetics was further developed by combining the theoretical model and transient state characterization, and the principle of the dynamic device can be revealed by the numerical simulator. On applying pulse stimulation, the dynamic device emulated the neuron synaptic response with frequency-dependent depression and facilitation, implying a great potential for future nonlinear and brain-inspired devices.

4.
Circulation ; 150(5): 350-361, 2024 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-38940005

RESUMO

BACKGROUND: Current estimates of atrial fibrillation (AF)-associated mortality rely on claims- or clinical-derived diagnoses of AF, limit AF to a binary entity, or are confounded by comorbidities. The objective of the present study is to assess the association between device-recognized AF and mortality among patients with cardiac implantable electronic devices capable of sensitive and continuous atrial arrhythmia detection. Secondary outcomes include relative mortality among cohorts with no AF, paroxysmal AF, persistent AF, and permanent AF. METHODS: Using the deidentified Optum Clinformatics US claims database (2015 to 2020) linked to the Medtronic CareLink database, we identified individuals with a cardiac implantable electronic device who transmitted data ≥6 months after implantation. AF burden was assessed during the first 6 months after implantation (baseline period). Subsequent mortality, assessed from claims data, was compared between patients with and without AF, with adjustment for age, geographic region, insurance type, Charlson Comorbidity Index, and implantation year. RESULTS: Of 21 391 patients (age, 72.9±10.9 years; 56.3% male) analyzed, 7798 (36.5%) had device-recognized AF. During a mean of 22.4±12.9 months (median, 20.1 [12.8-29.7] months) of follow-up, the overall incidence of mortality was 13.5%. Patients with AF had higher adjusted all-cause mortality than patients without AF (hazard ratio, 1.29 [95% CI, 1.20-1.39]; P<0.001). Among those with AF, patients with nonparoxysmal AF had the greatest risk of mortality (persistent AF versus paroxysmal AF: hazard ratio, 1.36 [95% CI, 1.18-1.58]; P<.001; permanent AF versus paroxysmal AF: hazard ratio, 1.23 [95% CI, 1.14-1.34]; P<.001). CONCLUSIONS: After adjustment for potential confounding factors, the presence of AF was associated with higher mortality in our cohort of patients with cardiac implantable electronic devices. Among those with AF, nonparoxysmal AF was associated with the greatest risk of mortality.


Assuntos
Fibrilação Atrial , Desfibriladores Implantáveis , Humanos , Fibrilação Atrial/mortalidade , Fibrilação Atrial/diagnóstico , Idoso , Masculino , Feminino , Pessoa de Meia-Idade , Idoso de 80 Anos ou mais , Marca-Passo Artificial , Fatores de Risco , Bases de Dados Factuais , Estados Unidos/epidemiologia
5.
Circulation ; 149(19): e1134-e1142, 2024 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-38545775

RESUMO

Wearable biosensors (wearables) enable continual, noninvasive physiologic and behavioral monitoring at home for those with pediatric or congenital heart disease. Wearables allow patients to access their personal data and monitor their health. Despite substantial technologic advances in recent years, issues with hardware design, data analysis, and integration into the clinical workflow prevent wearables from reaching their potential in high-risk congenital heart disease populations. This science advisory reviews the use of wearables in patients with congenital heart disease, how to improve these technologies for clinicians and patients, and ethical and regulatory considerations. Challenges related to the use of wearables are common to every clinical setting, but specific topics for consideration in congenital heart disease are highlighted.


Assuntos
American Heart Association , Técnicas Biossensoriais , Cardiopatias Congênitas , Dispositivos Eletrônicos Vestíveis , Humanos , Cardiopatias Congênitas/diagnóstico , Técnicas Biossensoriais/instrumentação , Estados Unidos
6.
Circulation ; 150(16): e280-e295, 2024 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-39253806

RESUMO

Early identification of kidney dysfunction in patients with advanced heart failure is crucial for timely interventions. In addition to elevations in serum creatinine, kidney dysfunction encompasses inadequate maintenance of sodium and volume homeostasis, retention of uremic solutes, and disrupted endocrine functions. Hemodynamic derangements and maladaptive neurohormonal upregulations contribute to fluctuations in kidney indices and electrolytes that may recover with guideline-directed medical therapy. Quantifying the extent of underlying irreversible intrinsic kidney disease is crucial in predicting whether optimization of congestion and guideline-directed medical therapy can stabilize kidney function. This scientific statement focuses on clinical management of patients experiencing kidney dysfunction through the trajectory of advanced heart failure, with specific focus on (1) the conceptual framework for appropriate evaluation of kidney dysfunction within the context of clinical trajectories in advanced heart failure, including in the consideration of advanced heart failure therapies; (2) preoperative, perioperative, and postoperative approaches to evaluation and management of kidney disease for advanced surgical therapies (durable left ventricular assist device/heart transplantation) and kidney replacement therapies; and (3) the key concepts in palliative care and decision-making processes unique to individuals with concomitant advanced heart failure and kidney disease.


Assuntos
Insuficiência Cardíaca , Nefropatias , Humanos , American Heart Association , Insuficiência Cardíaca/terapia , Insuficiência Cardíaca/fisiopatologia , Insuficiência Cardíaca/diagnóstico , Insuficiência Cardíaca/complicações , Coração Auxiliar , Rim/fisiopatologia , Nefropatias/diagnóstico , Nefropatias/etiologia , Nefropatias/fisiopatologia , Nefropatias/terapia , Cuidados Paliativos/métodos , Estados Unidos/epidemiologia , Literatura de Revisão como Assunto
7.
Circulation ; 149(14): e1051-e1065, 2024 04 02.
Artigo em Inglês | MEDLINE | ID: mdl-38406869

RESUMO

Cardiogenic shock continues to portend poor outcomes, conferring short-term mortality rates of 30% to 50% despite recent scientific advances. Age is a nonmodifiable risk factor for mortality in patients with cardiogenic shock and is often considered in the decision-making process for eligibility for various therapies. Older adults have been largely excluded from analyses of therapeutic options in patients with cardiogenic shock. As a result, despite the association of advanced age with worse outcomes, focused strategies in the assessment and management of cardiogenic shock in this high-risk and growing population are lacking. Individual programs oftentimes develop upper age limits for various interventional strategies for their patients, including heart transplantation and durable left ventricular assist devices. However, age as a lone parameter should not be used to guide individual patient management decisions in cardiogenic shock. In the assessment of risk in older adults with cardiogenic shock, a comprehensive, interdisciplinary approach is central to developing best practices. In this American Heart Association scientific statement, we aim to summarize our contemporary understanding of the epidemiology, risk assessment, and in-hospital approach to management of cardiogenic shock, with a unique focus on older adults.


Assuntos
Transplante de Coração , Coração Auxiliar , Humanos , Idoso , Choque Cardiogênico/diagnóstico , Choque Cardiogênico/epidemiologia , Choque Cardiogênico/terapia , American Heart Association , Resultado do Tratamento
8.
Annu Rev Med ; 74: 401-412, 2023 01 27.
Artigo em Inglês | MEDLINE | ID: mdl-35901314

RESUMO

Understanding how biases originate in medical technologies and developing safeguards to identify, mitigate, and remove their harms are essential to ensuring equal performance in all individuals. Drawing upon examples from pulmonary medicine, this article describes how bias can be introduced in the physical aspects of the technology design, via unrepresentative data, or by conflation of biological with social determinants of health. It then can be perpetuated by inadequate evaluation and regulatory standards. Research demonstrates that pulse oximeters perform differently depending on patient race and ethnicity. Pulmonary function testing and algorithms used to predict healthcare needs are two additional examples of medical technologies with racial and ethnic biases that may perpetuate health disparities.


Assuntos
Etnicidade , Disparidades em Assistência à Saúde , Humanos , Viés
9.
Circ Res ; 132(5): 652-670, 2023 03 03.
Artigo em Inglês | MEDLINE | ID: mdl-36862812

RESUMO

Wearable devices, such as smartwatches and activity trackers, are commonly used by patients in their everyday lives to manage their health and well-being. These devices collect and analyze long-term continuous data on measures of behavioral or physiologic function, which may provide clinicians with a more comprehensive view of a patients' health compared with the traditional sporadic measures captured by office visits and hospitalizations. Wearable devices have a wide range of potential clinical applications ranging from arrhythmia screening of high-risk individuals to remote management of chronic conditions such as heart failure or peripheral artery disease. As the use of wearable devices continues to grow, we must adopt a multifaceted approach with collaboration among all key stakeholders to effectively and safely integrate these technologies into routine clinical practice. In this Review, we summarize the features of wearable devices and associated machine learning techniques. We describe key research studies that illustrate the role of wearable devices in the screening and management of cardiovascular conditions and identify directions for future research. Last, we highlight the challenges that are currently hindering the widespread use of wearable devices in cardiovascular medicine and provide short- and long-term solutions to promote increased use of wearable devices in clinical care.


Assuntos
Fármacos Cardiovasculares , Insuficiência Cardíaca , Doença Arterial Periférica , Dispositivos Eletrônicos Vestíveis , Humanos , Hospitalização
10.
Brain ; 147(6): 2038-2052, 2024 Jun 03.
Artigo em Inglês | MEDLINE | ID: mdl-38195196

RESUMO

In Parkinson's disease, imbalances between 'antikinetic' and 'prokinetic' patterns of neuronal oscillatory activity are related to motor dysfunction. Invasive brain recordings from the motor network have suggested that medical or surgical therapy can promote a prokinetic state by inducing narrowband gamma rhythms (65-90 Hz). Excessive narrowband gamma in the motor cortex promotes dyskinesia in rodent models, but the relationship between narrowband gamma and dyskinesia in humans has not been well established. To assess this relationship, we used a sensing-enabled deep brain stimulator system, attached to both motor cortex and basal ganglia (subthalamic or pallidal) leads, paired with wearable devices that continuously tracked motor signs in the contralateral upper limbs. We recorded 984 h of multisite field potentials in 30 hemispheres of 16 subjects with Parkinson's disease (2/16 female, mean age 57 ± 12 years) while at home on usual antiparkinsonian medications. Recordings were done 2-4 weeks after implantation, prior to starting therapeutic stimulation. Narrowband gamma was detected in the precentral gyrus, subthalamic nucleus or both structures on at least one side of 92% of subjects with a clinical history of dyskinesia. Narrowband gamma was not detected in the globus pallidus. Narrowband gamma spectral power in both structures co-fluctuated similarly with contralateral wearable dyskinesia scores (mean correlation coefficient of ρ = 0.48 with a range of 0.12-0.82 for cortex, ρ = 0.53 with a range of 0.5-0.77 for subthalamic nucleus). Stratification analysis showed the correlations were not driven by outlier values, and narrowband gamma could distinguish 'on' periods with dyskinesia from 'on' periods without dyskinesia. Time lag comparisons confirmed that gamma oscillations herald dyskinesia onset without a time lag in either structure when using 2-min epochs. A linear model incorporating the three oscillatory bands (beta, theta/alpha and narrowband gamma) increased the predictive power of dyskinesia for several subject hemispheres. We further identified spectrally distinct oscillations in the low gamma range (40-60 Hz) in three subjects, but the relationship of low gamma oscillations to dyskinesia was variable. Our findings support the hypothesis that excessive oscillatory activity at 65-90 Hz in the motor network tracks with dyskinesia similarly across both structures, without a detectable time lag. This rhythm may serve as a promising control signal for closed-loop deep brain stimulation using either cortical or subthalamic detection.


Assuntos
Estimulação Encefálica Profunda , Ritmo Gama , Córtex Motor , Doença de Parkinson , Humanos , Doença de Parkinson/fisiopatologia , Feminino , Masculino , Pessoa de Meia-Idade , Ritmo Gama/fisiologia , Estimulação Encefálica Profunda/métodos , Córtex Motor/fisiopatologia , Idoso , Adulto , Discinesias/fisiopatologia , Discinesias/etiologia , Núcleo Subtalâmico/fisiopatologia , Rede Nervosa/fisiopatologia
11.
Proc Natl Acad Sci U S A ; 119(34): e2207767119, 2022 08 23.
Artigo em Inglês | MEDLINE | ID: mdl-35969749

RESUMO

Untethered soft miniature robots capable of accessing hard-to-reach regions can enable new, disruptive, and minimally invasive medical procedures. However, once the control input is removed, these robots easily move from their target location because of the dynamic motion of body tissues or fluids, thereby restricting their use in many long-term medical applications. To overcome this, we propose a wireless spring-preloaded barbed needle release mechanism, which can provide up to 1.6 N of force to drive a barbed needle into soft tissues to allow robust on-demand anchoring on three-dimensional (3D) surfaces. The mechanism is wirelessly triggered using radio-frequency remote heating and can be easily integrated into existing untethered soft robotic platforms without sacrificing their mobility. Design guidelines aimed at maximizing anchoring over the range of the most biological tissues (kPa range) and extending the operating depth of the device inside the body (up to 75%) are also presented. Enabled by these advances, we achieve robust anchoring on a variety of ex vivo tissues and demonstrate the usage of such a device when integrated with existing soft robotic platforms and medical imaging. Moreover, by simply changing the needle, we demonstrate additional functionalities such as controlled detachment and subsurface drug delivery into 3D cancer spheroids. Given these capabilities, our proposed mechanism could enable the development of a new class of biomedical-related functionalities, such as local drug delivery, disease monitoring, and hyperthermia for future untethered soft medical robots.


Assuntos
Robótica , Sistemas de Liberação de Medicamentos , Movimento (Física) , Robótica/métodos
12.
Proc Natl Acad Sci U S A ; 119(35): e2202118119, 2022 08 30.
Artigo em Inglês | MEDLINE | ID: mdl-35994641

RESUMO

Textiles hold great promise as a soft yet durable material for building comfortable robotic wearables and assistive devices at low cost. Nevertheless, the development of smart wearables composed entirely of textiles has been hindered by the lack of a viable sheet-based logic architecture that can be implemented using conventional fabric materials and textile manufacturing processes. Here, we develop a fully textile platform for embedding pneumatic digital logic in wearable devices. Our logic-enabled textiles support combinational and sequential logic functions, onboard memory storage, user interaction, and direct interfacing with pneumatic actuators. In addition, they are designed to be lightweight, easily integrable into regular clothing, made using scalable fabrication techniques, and durable enough to withstand everyday use. We demonstrate a textile computer capable of input-driven digital logic for controlling untethered wearable robots that assist users with functional limitations. Our logic platform will facilitate the emergence of future wearables powered by embedded fluidic logic that fully leverage the innate advantages of their textile construction.


Assuntos
Robótica , Indústria Têxtil , Têxteis , Dispositivos Eletrônicos Vestíveis , Biotecnologia , Lógica
13.
Proc Natl Acad Sci U S A ; 119(40): e2205922119, 2022 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-36161907

RESUMO

In soft devices, complex actuation sequences and precise force control typically require hard electronic valves and microcontrollers. Existing designs for entirely soft pneumatic control systems are capable of either digital or analog operation, but not both, and are limited by speed of actuation, range of pressure, time required for fabrication, or loss of power through pull-down resistors. Using the nonlinear mechanics intrinsic to structures composed of soft materials-in this case, by leveraging membrane inversion and tube kinking-two modular soft components are developed: a piston actuator and a bistable pneumatic switch. These two components combine to create valves capable of analog pressure regulation, simplified digital logic, controlled oscillation, nonvolatile memory storage, linear actuation, and interfacing with human users in both digital and analog formats. Three demonstrations showcase the capabilities of systems constructed from these valves: 1) a wearable glove capable of analog control of a soft artificial robotic hand based on input from a human user's fingers, 2) a human-controlled cushion matrix designed for use in medical care, and 3) an untethered robot which travels a distance dynamically programmed at the time of operation to retrieve an object. This work illustrates pathways for complementary digital and analog control of soft robots using a unified valve design.

14.
Eur Heart J ; 45(3): 161-177, 2024 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-37638967

RESUMO

BACKGROUND AND AIMS: The European Union Medical Device Regulation 2017/745 challenges key stakeholders to follow transparent and rigorous approaches to the clinical evaluation of medical devices. The purpose of this study is a systematic evaluation of published clinical evidence underlying selected high-risk cardiovascular medical devices before and after market access in the European Union (CE-marking) between 2000 and 2021. METHODS: Pre-specified strategies were applied to identify published studies of prospective design evaluating 71 high-risk cardiovascular devices in seven different classes (bioresorbable coronary scaffolds, left atrial appendage occlusion devices, transcatheter aortic valve implantation systems, transcatheter mitral valve repair/replacement systems, surgical aortic and mitral heart valves, leadless pacemakers, subcutaneous implantable cardioverter-defibrillator). The search time span covered 20 years (2000-21). Details of study design, patient population, intervention(s), and primary outcome(s) were summarized and assessed with respect to timing of the corresponding CE-mark approval. RESULTS: At least one prospective clinical trial was identified for 70% (50/71) of the pre-specified devices. Overall, 473 reports of 308 prospectively designed studies (enrolling 97 886 individuals) were deemed eligible, including 81% (251/308) prospective non-randomized clinical trials (66 186 individuals) and 19% (57/308) randomized clinical trials (31 700 individuals). Pre-registration of the study protocol was available in 49% (150/308) studies, and 16% (48/308) had a peer-reviewed publicly available protocol. Device-related adverse events were evaluated in 82% (253/308) of studies. An outcome adjudication process was reported in 39% (120/308) of the studies. Sample size was larger for randomized in comparison to non-randomized trials (median of 304 vs. 100 individuals, P < .001). No randomized clinical trial published before CE-mark approval for any of the devices was identified. Non-randomized clinical trials were predominantly published after the corresponding CE-mark approval of the device under evaluation (89%, 224/251). Sample sizes were smaller for studies published before (median of 31 individuals) than after (median of 135 individuals) CE-mark approval (P < .001). Clinical trials with larger sample sizes (>50 individuals) and those with longer recruitment periods were more likely to be published after CE-mark approval, and were more frequent during the period 2016-21. CONCLUSIONS: The quantity and quality of publicly available data from prospective clinical investigations across selected categories of cardiovascular devices, before and after CE approval during the period 2000-21, were deemed insufficient. The majority of studies was non-randomized, with increased risk of bias, and performed in small populations without provision of power calculations, and none of the reviewed devices had randomized trial results published prior to CE-mark certification.


Assuntos
Sistema Cardiovascular , Substituição da Valva Aórtica Transcateter , Humanos , Coração , Próteses e Implantes , União Europeia
15.
Eur Heart J ; 2024 Oct 29.
Artigo em Inglês | MEDLINE | ID: mdl-39474906

RESUMO

BACKGROUND AND AIMS: Data from randomized trials investigating different access closure strategies after transfemoral transcatheter aortic valve implantation (TF-TAVI) remain scarce. In this study, two vascular closure device (VCD) strategies to achieve hemostasis after TF-TAVI were compared. METHODS: The ACCESS-TAVI (Comparison of Strategies for Vascular ACCESS Closure after Transcatheter Aortic Valve Implantation) is a prospective, multicenter trial in which patients undergoing TF-TAVI were randomly assigned to a strategy with a combined suture-/plug-based VCD strategy (suture/plug group) using one ProGlideTM/ProStyleTM (Abbott Vascular) and one Angio-Seal® (Terumo) versus a suture-based VCD strategy (suture-only group) using two ProGlidesTM/ProStylesTM. The primary endpoint was a composite of major or minor access site-related vascular complications during index hospitalization according to Valve Academic Research Consortium (VARC)-3 criteria. Key secondary endpoints included time to hemostasis, VARC-3 bleeding type ≥2 and all-cause mortality over 30 days. RESULTS: Between September 2022 and April 2024, 454 patients were randomized. The primary endpoint occurred in 27% (62/230) in the suture/plug group and 54% (121/224) in the suture-only group (relative risk [RR] 0.55 [95% confidence interval: 0.44;0.68]; p<0.001). Time to hemostasis was significantly shorter in the suture/plug group compared to the suture-only group (108±208 s vs. 206±171 s; p <0.001). At 30 days, bleeding type ≥2 occurred less often in the suture/plug group compared to the sutureonly group (6.2% vs. 12.1%, RR 0.66 [0.43;1.02]; p=0.032), with no significant difference in mortality. CONCLUSIONS: With regard to the composite of major or minor access-related vascular complications, a combined suture-/plug-based VCD strategy was superior to a suturebased VCD strategy for vascular access closure in patients undergoing TF-TAVI.

16.
Nano Lett ; 24(22): 6488-6495, 2024 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-38771151

RESUMO

Understanding heating and cooling mechanisms in mesoscopic superconductor-semiconductor devices is crucial for their application in quantum technologies. Owing to their poor thermal conductivity, heating effects can drive superconducting-to-normal transitions even at low bias, observed as sharp conductance dips through the loss of Andreev excess currents. Tracking such dips across magnetic field, cryostat temperature, and applied microwave power allows us to uncover cooling bottlenecks in different parts of a device. By applying this "Joule spectroscopy" technique, we analyze heat dissipation in devices based on InAs-Al nanowires and reveal that cooling of superconducting islands is limited by the rather inefficient electron-phonon coupling, as opposed to grounded superconductors that primarily cool by quasiparticle diffusion. We show that powers as low as 50-150 pW are able to suppress superconductivity on the islands. Applied microwaves lead to similar heating effects but are affected by the interplay of the microwave frequency and the effective electron-phonon relaxation time.

17.
Nano Lett ; 2024 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-39373272

RESUMO

Supramolecular polymers hold promise in thermal management applications due to their multistability, high responsiveness, and cost-effectiveness. In this work, we successfully regulate phonon transport at the molecular level in supramolecular polymers by adjusting the strength of intermolecular hydrogen bonding. We synthesized three supramolecular polymer fibers with thermal conductivity differences of up to 289% based on melamine (M) and three simple positional isomers of hydroxybenzoic acid. Differential Scanning Calorimetry (DSC) measurement revealed discrepancies in thermal stability of the polymers, where structures with higher stability exhibited enhanced thermal conductivity. Fourier Transform Infrared Spectroscopy (FTIR) measurement and Density Functional Theory (DFT) calculations indicate that these differences arise from variations in hydrogen-bonding strengths at different bonding sites. Higher hydrogen-bonding strength leads to more stable thermal pathways, reduces phonon scattering, and increases thermal conductivity. Our findings provide valuable insights into controlling the thermal conductivity of polymer fibers, paving the way for applications in phonon-based thermal devices.

18.
Nano Lett ; 24(28): 8709-8716, 2024 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-38976365

RESUMO

Sealing wet porous membranes is a major challenge when fabricating cell encapsulation devices. Herein, we report the development of an Autoclavable Transparent Thermal Cutter (ATTC) for reliably sealing wet nanofibrous membranes. Notably, the ATTC is autoclavable and transparent, thus enabling in situ visualization of the sealing process in a sterile environment and ensuring an appropriate seal. In addition, the ATTC could generate smooth, arbitrary-shaped sealing ends with excellent mechanical properties when sealing PA6, PVDF, and TPU nanofibrous tubes and PP microporous membranes. Importantly, the ATTC could reliably seal wet nanofibrous tubes, which can shoulder a burst pressure up to 313.2 ± 19.3 kPa without bursting at the sealing ends. Furthermore, the ATTC sealing process is highly compatible with the fabrication of cell encapsulation devices, as verified by viability, proliferation, cell escape, and cell function tests. We believe that the ATTC could be used to reliably seal cell encapsulation devices with minimal side effects.

19.
Nano Lett ; 24(30): 9353-9359, 2024 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-39037901

RESUMO

The unique optical properties of graphene, with broadband absorption and ultrafast response, make it a critical component of optoelectronic and spintronic devices. Using time-resolved momentum microscopy with high data rate and high dynamic range, we report momentum-space measurements of electrons promoted to the graphene conduction band with visible light and their subsequent relaxation. We observe a pronounced nonthermal distribution of nascent photoexcited electrons with lattice pseudospin polarization in remarkable agreement with results of simple tight-binding theory. By varying the excitation fluence, we vary the relative importance of electron-electron vs electron-phonon scattering in the relaxation of the initial distribution. Increasing the excitation fluence results in increased noncollinear electron-electron scattering and reduced pseudospin polarization, although up-scattered electrons retain a degree of polarization. These detailed momentum-resolved electron dynamics in graphene demonstrate the capabilities of high-performance time-resolved momentum microscopy in the study of 2D materials and can inform the design of graphene devices.

20.
Nano Lett ; 24(27): 8394-8401, 2024 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-38865258

RESUMO

Hybrid semiconductor-superconductor nanowires have emerged as a cornerstone in modern quantum devices. Integrating such nanowires into hybrid devices typically requires extensive postgrowth processing which may affect device performance unfavorably. Here, we present a technique for in situ shadowing superconductors on nanowires and compare the structural and electronic properties of Al junctions formed by shadowing versus etching. Based on transmission electron microscopy, we find that typical etching procedures lead to atomic-scale surface roughening. This surface perturbation may cause a reduction of the electron mobility as demonstrated in transport measurements. Further, we display advanced shadowing geometries aiding in the pursuit of bringing fabrication of hybrid devices in situ. Finally, we give examples of shadowed junctions exploited in various device geometries that exhibit high-quality quantum transport signatures.

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