Advances in high-performance MEMS pressure sensors: design, fabrication, and packaging.

Pressure sensors play a vital role in aerospace, automotive, medical, and consumer electronics. Although microelectromechanical system (MEMS)-based pressure sensors have been widely used for decades, new trends in pressure sensors, including higher sensitivity, higher accuracy, better multifunctionality, smaller chip size, and smaller package size, have recently emerged. The demand for performance upgradation has led to breakthroughs in sensor materials, design, fabrication, and packaging methods, which have emerged frequently in recent decades. This paper reviews common new trends in MEMS pressure sensors, including minute differential pressure sensors (MDPSs), resonant pressure sensors (RPSs), integrated pressure sensors, miniaturized pressure chips, and leadless pressure sensors. To realize an extremely sensitive MDPS with broad application potential, including in medical ventilators and fire residual pressure monitors, the "beam-membrane-island" sensor design exhibits the best performance of 66 µV/V/kPa with a natural frequency of 11.3 kHz. In high-accuracy applications, silicon and quartz RPS are analyzed, and both materials show ±0.01%FS accuracy with respect to varying temperature coefficient of frequency (TCF) control methods. To improve MEMS sensor integration, different integrated "pressure + x" sensor designs and fabrication methods are compared. In this realm, the intercoupling effect still requires further investigation. Typical fabrication methods for microsized pressure sensor chips are also reviewed. To date, the chip thickness size can be controlled to be <0.1 mm, which is advantageous for implant sensors. Furthermore, a leadless pressure sensor was analyzed, offering an extremely small package size and harsh environmental compatibility. This review is structured as follows. The background of pressure sensors is first presented. Then, an in-depth introduction to MEMS pressure sensors based on different application scenarios is provided. Additionally, their respective characteristics and significant advancements are analyzed and summarized. Finally, development trends of MEMS pressure sensors in different fields are analyzed.

Functionalized nanopores based on hybridization chain reaction: Fabrication and microRNA sensing.

Enzyme-free hybridization chain reaction (HCR) technology is often used as a signal amplification tool for the detection of different targets. In this study, an ultrasensitive and label-free method for detecting miRNA-21 was developed using the nanopore ionic current rectification (ICR) technology coupled with HCR technology. The probe oligonucleotide (DNA1) was combined with the gold-coated nanopore through the Au-S bond to form a DNA1-functionalized gold-coated nanopore (DNA1-Au-coated nanopore). Since miRNA-21 is partially complementary to DNA1, it can be selectively recognized by DNA1-functionalized gold-coated nanopores. The target (miRNA-21) can induce the opening of hairpin DNA and HCR reaction after the introduction of hairpin DNA H1 and H2. The concentration of miRNA-21 will affect the combination of H1 and H2 on the inner wall of the nanopore, and its surface charge will change with the internal modification, thereby changing the ion current rectification ratio. Under the condition that the concentration of H1, H2 and HCR reaction time are constant, the change of ICR ratio is linearly correlated with the logarithm of miRNA-21 concentration within a certain range, which shows that the sensing strategy we designed can achieve target miRNA-21 detection. This ultrasensitive miRNA holds great promise in the field of cancer diagnosis.

G-quadruplex-hemin DNAzyme functionalized nanopipettes: Fabrication and sensing application.

Solid-nanopores/nanopipettes have the exquisite ability to reveal the changes in molecular volume due to the advantages of adjustable size, good rigidity and low noise. Herein, a new platform for sensing application was established based on G-quadruplex-hemin DNAzyme (GQH) functionalized gold-coated nanopipettes. In this method, GQH was immobilized on gold-coated nanopipette, which could be used as a catalyst for the reaction of H2O2 with 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) to promote the conversion of ABTS to ABTS+ ions inside gold-coated nanopipette, and the change of transmembrane ion current could be monitored in real time. At the optimal conditions, there was a correlation between the ion current and the concentration of H2O2 in a certain range, which could be used for the hydrogen peroxide sensing. The GQH immobilized nanopipette provides a useful platform to investigate enzymatic catalysis in confined environment, which can be used in electrocatalysis, sensing and fundamental electrochemistry.

Single gold nanowire-based nanosensor for adenosine triphosphate sensing by using in-situ surface-enhanced Raman scattering technique.

Development of new hot spots for surface enhanced Raman scattering (SERS) technique is of great significance recently. Herein, we developed a single Au nanowire (NW)-based nanosensor for adenosine triphosphate (ATP) sensing by using in-situ SERS technique. Single Au NWs, fabricated by laser-assisted pulling method and hydrofluoric acid (HF) etching process, were linked with single-stranded HS-terminated DNA. After that, gold-silver bimetallic nanoparticles (Au/Ag NPs), attached with thiol-containing Raman dyes and ATP aptamer, were immobilized on DNA-modified single AuNW due to the designed affinity between ATP aptamer and single-stranded DNA. This single AuNW-based device exhibited strong SERS signals. In the presence of adenosine triphosphate (ATP), due to the strong specific affinity between the aptamer and the target, the Au/Ag NPs will be separated from the AuNW, resulting in the obvious decrease of the Raman signals, which can be used for ATP sensing with high sensitivity, selectivity and stability. This nanosensor can be used as an ideal platform for real applications, especially at some confined-space samples, such as trace detection, single cell and in vivo analysis.

Whole-exome sequencing reveals MYH7 p.R671C mutation in three different phenotypes of familial hypertrophic cardiomyopathy.

Familial hypertrophic cardiomyopathy (HCM) is one of the most common types of genetic heart disorder and features high genetic heterogeneity. HCM is a major cause of sudden cardiac death and also an important cause of heart failure-related disability. A pedigree with suspected familial HCM was recruited for the present study to identify genetic abnormalities. HCM was confirmed by echocardiography and clinical data of the family members were collected. Genomic DNA was extracted from the peripheral blood and sequenced based on standard whole-exome sequencing (WES) protocols. Sanger sequencing was further performed to verify mutation sites and their association with HCM. WES and Sanger sequencing revealed a heterozygous missense mutation (c.2011C>T p.R671C) in myosin heavy chain 7 (MYH7) that was identified in three family members. The Arg671Cys mutation was located in exon 18 and, to the best of our knowledge, has not been previously reported in familial HCM. Furthermore, family members carrying the same mutated gene were of different sexes and clinical phenotypes. They included the proband, a 17-year-old survivor of sudden cardiac arrest with ventricular systolic dysfunction, the proband's maternal uncle, who presented with ventricular diastolic dysfunction and the proband's mother, who had no obvious clinical symptoms and did not present with cardiac dysfunction. However, echocardiology indicated that the proband's mother had an enlarged left atrium, slightly thicker right anterior wall and anterior septum and an expanded atrial septum. Therefore, HCM exhibited obvious genetic and phenotypic heterogeneity. To the best of our knowledge, the present study was the first to report such a mutation in the MYH7 gene in familial HCM. In addition, the present study demonstrated that WES is a powerful tool for identifying genetic variants in HCM.

Au-assisted polymerization of conductive poly(N-phenylglycine) as high-performance positive electrodes for asymmetric supercapacitors.

Herein, a novel conductive poly(N-phenylglycine) (PNPG) polymer was successfully prepared, byin situelectrochemical polymerization method (+0.75 VversusAg/AgCl) for 10 min, on flexible stainless-steel plate coated with a thin Au film (Au/SS) to serve as a binder-free pseudocapacitive PNPG/Au/SS electrode for energy storage devices. Compared to the electrode without Au coating, PNPG/Au/SS electrode exhibited better electrochemical performance with larger specific capacitance (495 F g-1at a current density of 2 A g-1), higher rate performance and lower resistance, which are good indications to act as a positive electrode for asymmetric supercapacitor devices. Combined with activated carbon as a negative electrode, an asymmetric supercapacitor device was constructed. It displayed a specific capacitance of 38 F g-1at a current density of 0.5 A g-1and an energy density of 5.3 Wh kg-1at a power density of 250 W kg-1. Experimentally, two asymmetric supercapacitor devices were connected in series to power a home-made windmill continuously for 8 s, revealing the high potential of this novel conductive polymer material for energy storage application.