In this paper, we report on the characterization of the sensitivity and the directionality of a novel ultrasonic hydrophone fabricated by micro-electro-mechanical systems (MEMS) process, using aluminum nitride (AlN) thin film as piezoelectric functional layer and exploiting a stress-driven design. Hydrophone structure and fabrication consist of four piezoelectric cantilevers in cross configuration, whose first resonant frequency mode in water is designed between 20 kHz and 200 kHz. The MEMS fabricated structures exploit 1 µm and 2 µm thick piezoelectric AlN thin film embedded between two molybdenum electrodes grown by DC magnetron sputtering on silicon (Si) wafer. The 200 nm thick molybdenum electrodes thin layers add a stress-gradient through cantilever thickness, leading to an out-of-plane cantilever bending. A water resistant parylene conformal coating of 1 µm was deposited on each cantilever for waterproof operation. AlN upward bent cantilevers show maximum sensitivity up to −163 dB. The cross configuration of four stress-driven piezoelectric cantilevers, combined with an opportune algorithm for processing all data sensors, permits a finer directionality response of this hydrophone.

Microelectrode arrays (MEAs) play a crucial role in investigating the electrophysiological activities of neuronal populations. Although two-dimensional neuronal cell cultures have predominated in neurophysiology in monitoring in-vitro the electrophysiological activity, recent research shifted toward culture using three-dimensional (3D) neuronal network structures for developing more sophisticated and realistic neuronal models. Nevertheless, many challenges remain in the electrophysiological analysis of 3D neuron cultures, among them the development of robust platforms for investigating the electrophysiological signal at multiple depths of the 3D neurons’ networks. While various 3D MEAs have been developed to probe specific depths within the layered nervous system, the fabrication of microelectrodes with different heights, capable of probing neural activity from the surface as well as from the different layers within the neural construct, remains challenging. This study presents a novel 3D MEA with microelectrodes of different heights, realized through a multi-stage mold-assisted electrodeposition process. Our pioneering platform allows meticulous control over the height of individual microelectrodes as well as the array topology, paving the way for the fabrication of 3D MEAs consisting of electrodes with multiple heights that could be tailored for specific applications and experiments. The device performance was characterized by measuring electrochemical impedance, and noise, and capturing spontaneous electrophysiological activity from neurospheroids derived from human induced pluripotent stem cells. These evaluations unequivocally validated the significant potential of our innovative multi-height 3D MEA as an avant-garde platform for in vitro 3D neuronal studies.

Introduction: Ropivacaine has been studied previously and holds promise as an agent that offers a safe, efficacious, and better recovery profile than other conventional agents such as bupivacaine. The aim of the present study was to compare the safety and efficacy of equal volume of different concentration of ropivacaine for epidural analgesia in patients undergoing major lower limb orthopedic surgery. Subjects and Methods: One hundred and fifty adult patients were randomized into three groups to receive single dose of equal volume of ropivacaine through epidural route in concentrations of 0.2%, 0.5%, and 0.75%, respectively. All the groups received equal dose of ropivacaine of same concentration for subarachnoid block using combined spinal-epidural technique. Results: Modified Bromage Scale and Numeric rating scale was used to assess motor block and analgesia. Data analysis was done using WINDOW SPSS Student Version 17 ANOVA test. Student's t-test was performed for comparison between two groups, and qualitative data were analyzed by applying Chi-square test. Conclusion: 0.5% and 0.75% ropivacaine were sufficient and effective for intrathecal subarachnoid block as well as for postoperative analgesia with epidural use. Shorter duration of motor blockade and analgesia was seen with ropivacaine 0.2%.

MEMS capacitive pressure sensors have proven to be more reliable in terms of temperature drift and long-term stability when compared to MEMS piezoresistive pressure sensors. In this study, a MEMS capacitive pressure sensor using micromachined technology has been designed and fabricated. As the movable electrode, a silicon membrane is used, while the fixed electrode is a gold metal film on a glass substrate. There is no deformation of the silicon membrane when the pressure is equal on both sides. As a result of the pressure of 0 kPa applied to the silicon membrane, a capacitance exists between it and the metal electrode. Differences in pressure on both sides of the silicon membrane will cause the membrane to deform. Silicon membranes deform due to pressure differences, which affect the capacitance between metal electrodes and silicon membranes. MEMS capacitive pressure sensors benefit from the superior mechanical properties of silicon material compared to metal-based sensors. Capacitive MEMS sensors are more desirable for applications requiring high performance and stability as compared to metal pressure sensors. This device is suited to measuring blood pressure with a measurement range of 0–45 kPa. When applied pressure was 0 kPa, the measurement capacitance was 3.61 pF, and when 45 kPa was applied, it was 7.19 pF.

In the pursuit of refining the fabrication of three-dimensional (3D) microelectrode arrays (MEAs), this study investigates the application of ultrasonic vibrations in template-assisted electrodeposition. This was driven by the need to overcome limitations in the deposition rate and the height uniformity of microstructures developed using conventional electrodeposition methods, particularly in the field of in vitro electrophysiological investigations. This study employs a template-assisted electrodeposition approach coupled with ultrasonic vibrations to enhance the deposition process. The method involves utilizing a polymeric hard mask to define the shape of electrodeposited microstructures (i.e., micro-pillars). The results show that the integration of ultrasonic vibrations significantly increases the deposition rate by up to 5 times and substantially improves the uniformity in 3D MEAs. The key conclusion drawn is that ultrasonic-enhanced template-assisted electrodeposition emerges as a powerful technique and enables the development of 3D MEAs at a higher rate and with a superior uniformity. This advancement holds promising implications for the precision of selective electrodeposition applications and signifies a significant stride in developing micro- and nanofabrication methodologies for biomedical applications.