Piezoresistive properties of low-firing temperature thick-films on steel sensors

Thick-film materials are very advantageous for piezoresistive pressure and force sensors because of ease of processing, reliability and low cost. The standard substrate material used with thick-film technology for sensing is alumina, but its elastic modulus is high and its strength rather low. Steels offer better mechanical properties and permit assembly without an elastomer seal, which is required for pressure sensing in severe conditions. In order to use the steel as substrate, the standard firing temperature of thick-films has been decreased. In previous studies, we have developed and characterized 2 low-firing thick-film systems (dielectrics, resistors and conductors) compatible with austenitic and ferritic materials. We have formulated these systems to achieve to chemical and thermal expansion compatibility. Other parameters like adherence, soldering properties and process, have been optimized too in order to be adapted on high-performance sensors. In this work, we will present the characterization of 2 steel sensors based on low fired thick-film technology: a high-performance pressure sensor based on high-strength steel substrate chemically similar to the ferritic steel, and a force sensor used in surgical operation of total knee arthroplasty (TKA) based on a medical alloy comparable to the austenitic steel. Key words: thick film system, high strength steel, pressure sensors, low-temperature firing

Study of the impact of high-voltage trimming on several characteristics of model TFRs and their stability

In this work we study in more details the impact of voltage trimming on different characteristics of model thick-film resistors (TFRs). Two series of RuO2-based TFRs with different conducting grain sizes are studied. As the composition of model pastes is completely known, it allows connecting the effects of trimming with the microscopic structure of the resistors.This study focuses on the change of resistivity, thermal coefficient of resistance, piezoresistivity and their post-trim stability. Those characteristics are studied as a function of conducting filler volume fraction. We show that the relative change of conductivity and the change in pezoresistivity due to voltage trimming are both diverging as the critical volume fraction, where the conductor/insulator transition occurs, is approached. It is also shown that voltage trimming changes the critical DC exponent, and can lead to a crossover from a nonuniversal to a universal behavior. We propose a description of voltage trimming which can explain the observed changes in characteristics of the samples. Key words: High-voltage Trimming, Thick- film resistors, Stabilit

High performance low-firing temperature thick-film pressure sensors on steel

Performance of piezoresistive thick-film pressure sensors on steel substrates is hindered by the high required firing temperatures of the layers, which cause degradation of the substrate mechanical properties. Special steels or alloys that are relatively unaffected by these temperatures are available, but their cost is very high. A much more promising alternative is the reduction of the thick-film firing temperature, in order to allow application of the standard high-strength steels used in thin-film cells. Therefore, a series of thick-film materials systems (dielectrics, resistors and conductors) firing at low temperatures (<700°C) on steel substrates has been developed and electrically characterised (sheet resistance and thermal coefficient of resistance – TCR). It was found that the main issue in these systems lies in mastering the materials interactions during firing, especially at the silver- based resistor terminations. The interaction of silver, resistor and dielectric tends to give rise to highly resistive zones at the terminations, affecting reliability. This can be circumvented by post-firing the resistor terminations at a moderate temperature. Key words: Thick-film materials, steel substrates, low-temperature processing, resistors, termination effect

Priming of natural killer cells by nonmucosal mononuclear phagocytes requires instructive signals from commensal microbiota.

Mononuclear phagocytes are an important component of an innate immune system perceived as a system ready to react upon encounter of pathogens. Here, we show that in response to microbial stimulation, mononuclear phagocytes residing in nonmucosal lymphoid organs of germ-free mice failed to induce expression of a set of inflammatory response genes, including those encoding the various type I interferons (IFN-I). Consequently, NK cell priming and antiviral immunity were severely compromised. Whereas pattern recognition receptor signaling and nuclear translocation of the transcription factors NF-κB and IRF3 were normal in mononuclear phagocytes of germ-free mice, binding to their respective cytokine promoters was impaired, which correlated with the absence of activating histone marks. Our data reveal a previously unrecognized role for postnatally colonizing microbiota in the introduction of chromatin level changes in the mononuclear phagocyte system, thereby poising expression of central inflammatory genes to initiate a powerful systemic immune response during viral infection

Prognostic Value of Right Ventricular Function in Patients With Suspected Myocarditis Undergoing Cardiac Magnetic Resonance

BACKGROUND Risk-stratification of myocarditis is based on functional parameters and tissue characterization of the left ventricle (LV), whereas right ventricular (RV) involvement remains mostly unrecognized. OBJECTIVES In this study, the authors sought to analyze the prognostic value of RV involvement in myocarditis by cardiac magnetic resonance (CMR). METHODS Patients meeting the recommended clinical criteria for suspected myocarditis were enrolled at 2 centers. Exclusion criteria were the evidence of coronary artery disease, pulmonary artery hypertension or structural cardiomyopathy. Biventricular ejection fraction, edema according to T2-weighted images, and late gadolinium enhancement (LGE) were linked to a composite end point of major adverse cardiovascular events (MACE), including heart failure hospitalization, ventricular arrhythmia, recurrent myocarditis, and death. RESULTS Among 1,125 consecutive patients, 736 (mean age: 47.8 ± 16.1 years) met the clinical diagnosis of suspected myocarditis and were followed for 3.7 years. Signs of RV involvement (abnormal right ventricular ejection fraction [RVEF], RV edema, and RV-LGE) were present in 188 (25.6%), 158 (21.5%), and 92 (12.5%) patients, respectively. MACE occurred in 122 patients (16.6%) and was univariably associated with left ventricular ejection fraction (LVEF), LV edema, LV-LGE, RV-LGE, RV edema, and RVEF. In a series of nesting multivariable Cox regression models, the addition of RVEF (HR$_{adj}$: 0.974 [95% CI: 0.956-0.993]; P = 0.006) improved prognostication (chi-square test = 89.5; P = 0.001 vs model 1; P = 0.006 vs model 2) compared with model 1 including only clinical variables (chi-square test = 28.54) and model 2 based on clinical parameters, LVEF, and LV-LGE extent (chi-square test = 78.93). CONCLUSIONS This study emphasizes the role of RV involvement in myocarditis and demonstrates the independent and incremental prognostic value of RVEF beyond clinical variables, CMR tissue characterization, and LV function. (Inflammatory Cardiomyopathy Bern Registry [FlamBER]; NCT04774549; CMR Features in Patients With Suspected Myocarditis [CMRMyo]; NCT03470571)

Prognostic Value of Right Ventricular Function in Patients With Suspected Myocarditis Undergoing Cardiac Magnetic Resonance.

BACKGROUND Risk-stratification of myocarditis is based on functional parameters and tissue characterization of the left ventricle (LV), whereas right ventricular (RV) involvement remains mostly unrecognized. OBJECTIVES In this study, the authors sought to analyze the prognostic value of RV involvement in myocarditis by cardiac magnetic resonance (CMR). METHODS Patients meeting the recommended clinical criteria for suspected myocarditis were enrolled at 2 centers. Exclusion criteria were the evidence of coronary artery disease, pulmonary artery hypertension or structural cardiomyopathy. Biventricular ejection fraction, edema according to T2-weighted images, and late gadolinium enhancement (LGE) were linked to a composite end point of major adverse cardiovascular events (MACE), including heart failure hospitalization, ventricular arrhythmia, recurrent myocarditis, and death. RESULTS Among 1,125 consecutive patients, 736 (mean age: 47.8 ± 16.1 years) met the clinical diagnosis of suspected myocarditis and were followed for 3.7 years. Signs of RV involvement (abnormal right ventricular ejection fraction [RVEF], RV edema, and RV-LGE) were present in 188 (25.6%), 158 (21.5%), and 92 (12.5%) patients, respectively. MACE occurred in 122 patients (16.6%) and was univariably associated with left ventricular ejection fraction (LVEF), LV edema, LV-LGE, RV-LGE, RV edema, and RVEF. In a series of nesting multivariable Cox regression models, the addition of RVEF (HRadj: 0.974 [95% CI: 0.956-0.993]; P = 0.006) improved prognostication (chi-square test = 89.5; P = 0.001 vs model 1; P = 0.006 vs model 2) compared with model 1 including only clinical variables (chi-square test = 28.54) and model 2 based on clinical parameters, LVEF, and LV-LGE extent (chi-square test = 78.93). CONCLUSIONS This study emphasizes the role of RV involvement in myocarditis and demonstrates the independent and incremental prognostic value of RVEF beyond clinical variables, CMR tissue characterization, and LV function. (Inflammatory Cardiomyopathy Bern Registry [FlamBER]; NCT04774549; CMR Features in Patients With Suspected Myocarditis [CMRMyo]; NCT03470571)