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Abstract: In this study, influence of coating chemistry, channel width and tortuosity of various two-dimensional micro-channels were explored on micromachined Si using osteoblast precursor cells line 1 (OPC1). The rationale for our study is to delineate the influence of different porosity parameters on bone cell attachment and proliferation in vitro. Channel widths of 100, 200, 300, 400, and 600μm; channel bends of 0, 1, and 2 right angles; and gold and silicon dioxide coatings on single-crystal Si were studied. Experiments were conducted with channel tops under glass covered and uncovered conditions keeping the channel depth at 220μm. Independent samples were evaluated using SEM imaging and MTT assay to measure bone cell morphology and quantity. Images were taken of micro-channels and exterior chambers at 50×, 500×, 1000×, and 5000× magnifications. Channel and chamber cell densities were scored as follows: bare (score=0), scattered (1), limited (2), abundant (3), and overflowing (4). Samples were then scored and statistically analyzed for major differences. In general, OPC1 cells proliferated at least 5% or better based on cell numbers under uncovered conditions than glass covered. Channel widths of 100μm largely prohibited cell proliferation and diffusion by narrow path inhibition with the lowest average score of 1.17. Among channel bends of 0, 1, and 2 right angles, an increase in micro-channel tortuosity from 0–2 bends amplified OPC1 cell growth upwards of ~6.6%. A one-way ANOVA showed significant differences in cell quantity for alternating channel tortuosity at a significance level of p <0.05. No preference was found for gold or silicon dioxide coatings on Si for bone cell proliferation. [Copyright &y& Elsevier]

Abstract: Piezoelectric micromachined ultrasonic transducers (pMUTs) were designed, fabricated and tested to measure resonance and anti-resonance frequencies, and quality factor. Film quality was monitored via saturation polarization, remnant polarization and coercive electric field measurements in different films. Effective coupling coefficient and device efficiency are calculated based on those measured values. Single and split top electrode pMUTs designs, X and Y, respectively, are evaluated to understand the influence of top electrode design on device performance. It was found that resonance frequency decreases with an increase in membrane width. Top electrodes, smaller than the membrane width by 10μm, show a positive effect on the effective coupling coefficient of the pMUTs. It was found that both quality factor and device efficiency are maximized when top electrode width is the same as that of membrane width. An increase in top electrode dimension beyond the membrane decreases device performance. [Copyright &y& Elsevier]

A spiral‐artificial basilar membrane (S‐ABM) sensor is reported that mimics the basilar membrane (BM) of the human cochlea and can detect sound by separating it into 24 sensing channels based on the frequency band. For this, an analytical function is proposed to design the width of the BM so that the frequency bands are linearly located along the length of the BM. To fabricate the S‐ABM sensor, a spiral‐shaped polyimide film is used as a vibrating membrane, with maximum displacement at locations corresponding to specific frequency bands of sound, and attach piezoelectric sensor modules made of poly(vinylidene fluoride‐trifluoroethylene) film on top of the polyimide film to measure the vibration amplitude at each channel location. As the result, the S‐ABM sensor implements a characteristic frequency band of 96‐12,821 Hz and 24‐independent critical bands. Using real‐time signals from discriminate channels, it is demonstrated that the sensor can rapidly identify the operational noises from equipment processes as well as vehicle sounds from environmental noises on the road. The sensor can be used in a variety of applications, including speech recognition, dangerous situation recognition, hearing aids, and cochlear implants, and more. [ABSTRACT FROM AUTHOR]

Highlights: This review discusses the potential of degradable metallic micromotors for a variety of biomedical and environmental applications. The design principles, fabrication techniques and degradation mechanisms of degradable metallic micromotors are reviewed in detail. Challenges and future directions for the development of degradable metallic micromotors for real-life applications are presented. Synthetic micromotor has gained substantial attention in biomedicine and environmental remediation. Metal-based degradable micromotor composed of magnesium (Mg), zinc (Zn), and iron (Fe) have promise due to their nontoxic fuel-free propulsion, favorable biocompatibility, and safe excretion of degradation products Recent advances in degradable metallic micromotor have shown their fast movement in complex biological media, efficient cargo delivery and favorable biocompatibility. A noteworthy number of degradable metal-based micromotors employ bubble propulsion, utilizing water as fuel to generate hydrogen bubbles. This novel feature has projected degradable metallic micromotors for active in vivo drug delivery applications. In addition, understanding the degradation mechanism of these micromotors is also a key parameter for their design and performance. Its propulsion efficiency and life span govern the overall performance of a degradable metallic micromotor. Here we review the design and recent advancements of metallic degradable micromotors. Furthermore, we describe the controlled degradation, efficient in vivo drug delivery, and built-in acid neutralization capabilities of degradable micromotors with versatile biomedical applications. Moreover, we discuss micromotors' efficacy in detecting and destroying environmental pollutants. Finally, we address the limitations and future research directions of degradable metallic micromotors. [ABSTRACT FROM AUTHOR]

The past decade has seen an upsurge in the development of small‐scale magnetic robots for various biomedical applications. However, many of the reported designs comprise components with biocompatibility concerns. Strategies for fabricating biocompatible and degradable microrobots are required. In this study, polyvinyl alcohol (PVA)‐based magnetic hydrogel microrobots with different morphologies and tunable stability are developed by combining a 3D printed template‐assisted casting with a salting‐out process. 3D sacrificial micromolds are prepared via direct laser writing to shape PVA‐magnetic nanoparticle composite hydrogel microrobots with high architectural complexity. By adjusting the PVA composition and salting‐out parameters, the hydrogel dissolubility can be customized. Due to their high mobility, tunable stability, and high biocompatibility, these PVA‐based magnetic microrobots are suitable platforms for targeted drug and cell delivery. [ABSTRACT FROM AUTHOR]

Mobile microvortices generated by rotating nickel (Ni) nanowires (NW) have been reported as capable of inducing fluidic trapping that can be precisely focused and translated to manipulate microobjects. Here, a new design for significantly enhanced fluidic trapping is reported, which is a dumbbell (DB)-shaped magnetic actuator, assembled by a Ni NW and two polystyrene microbeads. In contrast to the single mode of tumbling trapping possessed by Ni NW, the magnetic dumbbell is able to perform dynamical trapping and implement on-demand transport of microobjects in three modes, i.e., tumbling, wobbling, and rolling. Experiments are conducted to demonstrate the robustness and efficacy of the fluidic trap by the DB actuator. And simulations using a finite element model compare the fluidic traps induced by NW and DB, followed by further discussion on the actuation and transport efficiency of NW and DB fluidic tweezers (FT). At last, some practical issues regarding the application of DB FT are addressed. [ABSTRACT FROM AUTHOR]

Magnetoelectric (ME) oxide materials can convert magnetic input into electric output and vice versa, making them excellent candidates for advanced sensing, data storage, and communication. However, their application has been limited to rigid devices due to their brittle nature. Here, flexible ME oxide composite (BaTiO3/CoFe2O4) thin film nanostructures with distinct ME coupling coefficients are reported. In contrast to rigid bulk counterparts, these ceramic nanostructures display a flexible behavior after being released from the substrate, and can be transferred onto a stretchable substrate such as polydimethylsiloxane. These ceramic films possess high ME coefficients due to minimized clamping effect and preferred crystalline orientation, and exhibit reversibly tunable ME coupling via mechanical stretching thanks to their large elasticity (>4%). It is believed that the study can open up new avenues for integrating ceramic ME composites into micro‐/nanoelectromechanical system and soft robotic devices. [ABSTRACT FROM AUTHOR]

A vector hydrophone is an underwater acoustic sensor that can detect the direction of a sound source. Wide-band characteristics and high sensitivity enhance the performance of underwater surveillance systems in complex environments. A vector hydrophone comprising a triaxial piezoelectric accelerometer and spherical hydrophone was fabricated and tested in the air and underwater. The vector hydrophone was designed to exceed the quantitative figures of merit (i.e., receiving voltage sensitivity and bandwidth) of commercially available hydrophones. Accelerometer performance was enhanced by placing a pair of piezoelectric single crystals on each axis and modifying the seismic mass material. The receiving voltage sensitivity of the omnidirectional hydrophone was approximately −160 dB relative to 1   V / μ Pa with the amplifier in water; the sensitivity of the accelerometer exceeded 300 mV/g in air and −215 dB relative to 1   V / μ Pa underwater over the frequency range of interest. The receiving directivity of the vector hydrophone was validated underwater, which confirmed that it could detect the direction of a sound source. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the efficacy of preoperative and intraoperative steroid administration for inner ear protection in cochlear implantation (CI). Nineteen subjects who underwent CI were included in the study, and 10 subjects were enrolled as controls (steroid-administered group, n = 19; control group, n = 10). Dexamethasone (dexamethasone sodium phosphate, 5 mg/ml) was systemically administered preoperatively (1 ml) and topically applied during CI (0.5 ml). The extent of hearing preservation (HP) after CI and the change in the bithermal caloric response were evaluated. Hearing level was calculated using mean thresholds [(250 Hz + 500 Hz + 1,000 Hz + 2,000 Hz)/4]. Preoperative hearing thresholds were similar in the steroid-administered and control groups (100.92 ± 12.60 vs. 103.29 ± 14.39 dB, p = 0.650). The mean thresholds significantly increased in both groups after surgery (108.46 ± 14.08 dB, p = 0.006, for the steroid-administered group; 117.50 ± 6.34 dB, p = 0.027, for the control group), and the difference between the groups was also significant (p = 0.027). The postoperative shift in the hearing thresholds at frequencies of 500 and 1,000 Hz was significant in the steroid-administered group and that at the frequencies of 500, 1,000 and 2,000 Hz was significant in the control group. However, the extent of the shift in hearing threshold levels at each frequency was not significantly different between the groups. Preservation of hearing thresholds was compared between the groups, and there were significantly more subjects with complete and partial HP in the steroid-administered group than in the control group (p = 0.008). The preoperative caloric response was maintained after CI in the steroid-administered group. This study suggests that the perioperative use of a steroid could minimize the inner ear damage after CI. [ABSTRACT FROM AUTHOR]

Background: Clinically, steroids have been used for hearing preservation both topically and systemically during cochlear implantation. Objective: This study compared steroid efficacy for hearing preservation among different types of delivery modes using an animal experiment. Materials and methods: For 76 guinea pigs, topical and systemic delivery methods, four pump types with different infusion rates, delivery durations, and total steroid amounts were used. Threshold changes of 8, 16, and 32 kHz after dummy electrode insertion were evaluated at 1 and 4 weeks and compared among delivery method and pump types. Inflammatory response in the cochlea was histologically compared. Results: For topical delivery groups, long-term release showed advantages in preserving hearing. Systemic delivery groups showed smaller threshold shifts than control group in all frequencies (p >.05). In short-term low dose application, compared to topical delivery, systemic delivery showed advantage in hearing preservation at both time point. However, others fail to show significant difference between two methods. Histologically, inflammatory response in the scala tympani at the basal turn was less in systemic delivery, especially in high dose and long-term. Conclusion and significance: The difference of hearing preservation was not obvious between two delivery methods. Higher dose and longer duration might have advantages in hearing preservation. [ABSTRACT FROM AUTHOR]

Objective: Interventional ultrasound imaging is a prerequisite for guiding implants and treatment within the hearts and blood vessels. Due to limitations on the catheter's diameter, interventional ultrasonic transducers have side-looking structures although forward-looking imaging may provide more intuitive and real time guidance in treating diseased sites ahead of catheters. To address the issue, a magnetically actuated forward-looking interventional ultrasound imaging device is implemented for the first time. Methods: A forward-looking catheter containing a 1 mm ring type focused 35 MHz ultrasound transducer and a micro magnet, was fabricated. For imaging, the transducer was placed at the center of four electromagnetic coils positioned on four sides of a squared acrylic housing. By modifying the magnetic field, the catheter tip could be remotely translated for sector scanning. Results: The scanning angle could reach up to 3° in 1 Hz with 15 mT, while wider angles of 5° could be achieved with a higher magnetic field of 25 mT for ex-vivo imaging. The position of the transducer could be detected by monitoring the motion with a CCD camera, mimicking clinical X-ray imaging. In the wire target and tissue mimicking phantom studies, the measured hole size, spatial resolution and distance between wires by the proposed system were comparable with the values from a linear scanner. Multi-frame real time data acquisition was demonstrated via ex-vivo imaging on a pig's coronary artery. Conclusion/Significance: The feasibility of magnetically actuated forward-looking interventional ultrasound imaging was demonstrated. The remote-controlled scanning method may allow to simplify the structures of forward-looking interventional ultrasound imaging catheters. [ABSTRACT FROM AUTHOR]

Neurodegenerative diseases generally result in irreversible neuronal damage and neuronal death. Cell therapy shows promise as a potential treatment for these diseases. However, the therapeutic targeted delivery of these cells and the in situ provision of a suitable microenvironment for their differentiation into functional neuronal networks remain challenging. A highly integrated multifunctional soft helical microswimmer featuring targeted neuronal cell delivery, on‐demand localized wireless neuronal electrostimulation, and post‐delivery enzymatic degradation is introduced. The helical soft body of the microswimmer is fabricated by two‐photon lithography of the photocurable gelatin–methacryloyl (GelMA)‐based hydrogel. The helical body is then impregnated with composite multiferroic nanoparticles displaying magnetoelectric features (MENPs). While the soft GelMA hydrogel chassis supports the cell growth, and is degraded by enzymes secreted by cells, the MENPs allow for the magnetic transportation of the bioactive chassis, and act as magnetically mediated electrostimulators of neuron‐like cells. The unique combination of the materials makes these microswimmers highly integrated devices that fulfill several requirements for their future translation to clinical applications, such as cargo delivery, cell stimulation, and biodegradability. The authors envision that these devices will inspire new avenues for targeted cell therapies for traumatic injuries and diseases in the central nervous system. [ABSTRACT FROM AUTHOR]

Abstract: Animals change sensory responses and their eventual behaviors, depending on their internal metabolic status and external food availability. However, the mechanisms underlying feeding state‐dependent behavioral changes remain undefined. Previous studies have shown that Caenorhabditis elegans hermaphrodite exhibits avoidance behaviors to acute exposure of a pheromone, ascr#3 (asc‐ΔC9, C9). Here, we show that the ascr#3 avoidance behavior is modulated by feeding state via the insulin signaling pathway. Starvation increases ascr#3 avoidance behavior, and loss‐of‐function mutations in daf‐2 insulin‐like receptor gene dampen this starvation‐induced ascr#3 avoidance behavior. DAF‐2 and its downstream signaling molecules, including the DAF‐16 FOXO transcription factor, act in the ascr#3‐sensing ADL neurons to regulate synaptic transmission to downstream target neurons, including the AVA command interneurons. Moreover, we found that starvation decreases the secretion of INS‐18 insulin‐like peptides from the intestine, which antagonizes DAF‐2 function in the ADL neurons. Altogether, this study provides insights about the molecular communication between intestine and sensory neurons delivering hunger message to sensory neurons, which regulates avoidance behavior from pheromones to facilitate survival chance. [ABSTRACT FROM AUTHOR]

Magnetically manipulated biodegradable microrobots that encapsulate drugs from the outset are produced in a novel, simple way using UV-laser micro-machining. This method enables multiple microrobots to be produced rapidly, without the need for post-drug encapsulation or polymerization by light exposure, which may cause the drug compound to denature. The microrobot consists of poly (dl-lactic-co-glycolic acid) (PLGA), iron (Fe) particles and 5-fluorouracil (5-FU) as biodegradable, magnetic and drug material, respectively. The fabricated microrobots are precisely and remotely controlled in a fluidic environment by external magnetic fields. To prove the feasibility of targeted drug delivery, the drug release is profiled as a function of time, biodegrading in aqueous solution at 37 °C over 6 weeks. The Fe concentration has a significant effect on the biodegradation rate of the microrobots. The amount of drug encapsulated can be controlled by adjusting the concentration of the drug in the PLGA/Fe/5-FU mixture whilst fabricating the microrobots. Approximately 0.013 μg of 5-FU is released from a single PLGA/Fe/5-FU microrobot over a period of 6 weeks. In addition, we have conducted drug testing with human colorectal cancer (HCT116) cells to investigate the effect of drugs released from our microrobots on cancer cells. While no significant reduction in live cell ratio was observed with the controls, it decreased approximately 20% when cells were cultured with the PLGA/Fe/5-FU microrobot for 2 days. It presents that 5-FU was delivered from the microrobot to cancer cells and negatively affected them. [ABSTRACT FROM AUTHOR]

This paper presents a novel Adaptive Genetic Algorithm for optimal path planning of multiple nanoparticles during the nanomanipulation process. The proposed approach determines the optimal manipulation path in the presence of surface roughness and environment obstacles by considering constraints imposed on the nanomanipulation process. In this research, first by discretizing the environment, an initial set of feasible paths were generated, and then, path optimization was continued in the original continuous environment (and not in the discrete environment). The presented novel approach for path planning in continuous environment (1) makes the algorithm independent of grid size, which is the main limitation in conventional path planning methods, and (2) creates a curve path, instead of piecewise linear one, which increases the accuracy and smoothness of the path considerably. Every path is evaluated based on three factors: the displacement effort (the area under critical force-time diagram during nanomanipulation), surface roughness along the path, and smoothness of the path. Using the weighted linear sum of the mentioned three factors as the objective function provides the opportunity to (1) find a path with optimal value for all factors, (2) increase/decrease the effect of a factor based on process considerations. While the former can be obtained by a simple weight tuning procedure introduced in this paper, the latter can be obtained by increasing/decreasing the weight value associated with a factor. In the case of multiple nanoparticles, a co-evolutionary adaptive algorithm is introduced to find the best destination for each nanoparticle, the best sequence of movement, and optimal path for each nanoparticle. By introducing two new operators, it was shown that the performance of the presented co-evolutionary mechanism outperforms the similar previous works. Finally, the proposed approach was also developed based on a modified Particle Swarm Optimization algorithm, and its performance was compared with the proposed Adaptive Genetic Algorithm. [ABSTRACT FROM AUTHOR]

On page 1604571, L. Zhang and co‐workers introduce a new design of a magnetic micromachine for significantly enhanced fluidic trapping, which has a dumbbell‐shape, composed of a nickel nanowire and two polystyrene microbeads. The magnetic dumbbell‐like micromachines are capable of performing dynamical trapping and implement on‐demand transport of microscale objects with induced microvortices in three locomotion modes, i.e., tumbling, wobbling, and rolling. [ABSTRACT FROM AUTHOR]

We report that ultra-thin tellurium (Te) nanoflakes were successfully grown on a sample of a gold-coated textile, which then was used as an active piezoelectric material. An output voltage of 4 V and a current of 300 nA were obtained from the bending test under a driving frequency of 10 Hz. To test the practical applications, Te nanoflake nanogenerator (TFNG) device was attached to the subject’s arm, and mechanical energy was converted to electrical energy by means of periodic arm-bending motions. The optimized open-circuit voltage and short-circuit current density of approximately 125 V and 17 μA/cm 2 , respectively, were observed when a TFNG device underwent a compression test with a compressive force of 8 N and driving frequency of 10 Hz. This high-power generation enabled the instantaneous powering of 10 green light-emitting diodes that shone without any assistance from an external power source. [ABSTRACT FROM AUTHOR]

Real-time reversible tuning of the ME coupling coefficient by stretching the elastomer has been realized in these composites. Magnetoelectric, micro-/nanoelectromechanical system, multiferroics, soft robotics, thin film Keywords: magnetoelectric; micro-/nanoelectromechanical system; multiferroics; soft robotics; thin film EN magnetoelectric micro-/nanoelectromechanical system multiferroics soft robotics thin film 1 1 1 03/28/23 20230315 NES 230315 B Ceramic Nanocomposites b In article number 2202097, Salvador Vidal Pané, Xiang-Zhong Chen, and co-workers present free-standing magnetoelectric (ME) ceramic nanocomposites with high ME coupling coefficients and large stretchability. [Extracted from the article]

Piezoelectric micromachined ultrasonic transducers (pMUTs) are of great interest for numerous applications, including fingerprint imaging, precise acoustic sensing, and ultrasonic medical imaging, due to their properties of high design freedom and low power consumption when miniaturized for a transducer array. However, micromachined transducers tend to have relatively low acoustic intensity compared with conventional ceramic-based transducers. Therefore, it is preferable and recommended to achieve high acoustic intensity and enhanced displacement of the pMUTs. This paper presents circular pMUTs with various clamped membranes and explores the displacement and mode shape of membranes at resonance frequencies that are critical for enhanced acoustic intensity. Each circular clamped membrane had four etched holes at the edge of the membrane to control the boundary condition, which affected the resonance frequencies and membrane displacement by controlling the effective stiffness. The displacement and effective area as a function of etching hole size were simulated using COMSOL software and verified experimentally. The maximum displacement of a membrane 60 µm in diameter exhibited a 25% improvement when the etching hole angle was 20° compared with the fully clamped membrane. The effective area for acoustic intensity increased from 54.2% to 61.7% at 60° when the mode shape changed from circular to square. The experimental and simulation results were in reasonable agreement, and the results helped clarify how the geometric design of the suspended membrane of the pMUT affects its vibrational characteristics. [Display omitted] • Piezoelectric micromachined ultrasonic transducers (pMUTs) with various etching holes were fabricated using surface micromachining. • The circular and fin-shaped etching holes were used to modify the boundary conditions of the pMUT membrane. • The experimental results for the effect of etching holes on vibrational characteristics agree with the COMSOL simulation results. • The various design of the etching hole provides a method to increase the output pressure of pMUT for ultrasonic application. [ABSTRACT FROM AUTHOR]

Background Quantitative electroencephalography (qEEG) is effective when used to analyze ongoing cortical oscillations in cochlear implant (CI) users. However, localization of cortical activity in such users via qEEG is confounded by the presence of artifacts produced by the device itself. Typically, independent component analysis (ICA) is used to remove CI artifacts in auditory evoked EEG signals collected upon brief stimulation and it is effective for auditory evoked potentials (AEPs). However, AEPs do not reflect the daily environments of patients, and thus, continuous EEG data that are closer to such environments are desirable. In this case, device-related artifacts in EEG data are difficult to remove selectively via ICA due to over-completion of EEG data removal in the absence of preprocessing. New methods EEGs were recorded for a long time under conditions of continuous auditory stimulation. To obviate the over-completion problem, we limited the frequency of CI artifacts to a significant characteristic peak and apply ICA artifact removal. Results Topographic brain mapping results analyzed via band-limited (BL)-ICA exhibited a better energy distribution, matched to the CI location, than data obtained using conventional ICA. Also, source localization data verified that BL-ICA effectively removed CI artifacts. Comparison with existing method The proposed method selectively removes CI artifacts from continuous EEG recordings, while ICA removal method shows residual peak and removes important brain activity signals. Conclusion CI artifacts in EEG data obtained during continuous passive listening can be effectively removed with the aid of BL-ICA, opening up new EEG research possibilities in subjects with CIs. [ABSTRACT FROM AUTHOR]

Conclusions: Continuous topical drug delivery using an osmotic pump is an effective supplementary technique for hearing preservation after cochlear implantation, as demonstrated in a guinea pig model. Objective: To evaluate the effect of continuous topical steroid delivery via an osmotic pump in an animal cochlear implant model. Methods: Twenty-three guinea pigs were used for the study. The animals were divided into three groups: control group ( n = 8), simple topical dexamethasone delivery group (sDEXA group, n = 7) and continuous topical dexamethasone delivery group (cDEXA, n = 8). The hearing thresholds of all animals were measured by pre-operative auditory brain stem responses (ABRs) at 2, 8, 16, 24, and 32 kHz. ABRs were re-evaluated after cochlear implantation, and the animals were sacrificed for hematoxylin and eosin staining. Results: The ABR threshold at 1 week post-operatively was significantly lower in the cDEXA group than in the control and sDEXA groups at most frequencies. Threshold shifts from baseline were statistically smaller in the cDEXA group than in the control and sDEXA groups at all frequencies. Histological analysis revealed decreased numbers of multi-nucleated giant cells and thinner histiocyte layers. [ABSTRACT FROM AUTHOR]

Most polymer-based biomedical implantable microscale devices have a smooth surface, so that cell seeding is suppressed in the absence of an adhesive material coating on the surface. SU-8 is a negative photoresist, and is widely used for the fabrication of micro-/nanoscale biomedical devices. A physical surface modification technique was introduced in this study to enhance cell viability and mobility on a SU-8 substrate. To characterize cell viability and mobility, four types of SU-8 substrate were prepared: flat bare substrate, poly- l -lysine (PLL)-coated flat bare substrate, nanoporous substrate, and PLL-coated nanoporous substrate. R at pheochromocytoma (PC12) cells were cultured on these substrates, and nerve growth factor (NGF) was added to induce differentiation of the PC12 cells. On the seventh day of cell culture, PC12 cells on the nanoporous SU-8 substrate showed 24.3% cell differentiation (neurite outgrowth) versus 1.1% cell differentiation on the flat bare substrate. It was also found that cells had a tendency to move from a flat surface to a nanoporous region. These cellular activities on the nanoporous SU-8 substrate suggest that nanopores can be used to regulate cellular activities and can be applied to SU-8-based microscale biomedical devices. [ABSTRACT FROM AUTHOR]

Two types of microfabricated acoustic transducers-the resonator array of isolated beams (RAIB) and the resonator array of coupled beams (RACB)-were built using MEMS technology. The frequency selectivity of the two types of transducers was qualitatively compared using the transfer functions measured with a scanning laser Doppler vibrometer (SLDV). Each RAIB beam operated as a band-pass filter in the proximity to the corresponding resonance frequency, thereby showing the frequency-selective feature of the basilar membrane (BM). However, the frequency selectivity of RACB was poor because the SiO membrane, which mechanically coupled the neighboring beams, suppressed the independent response of each beam. The influence of the mechanical coupling of the SiO membrane was simulated using lumped parametric models. Simulation results showed that the coupling stiffness of the SiO membrane may significantly undermine the frequency selectivity of the resonator array. The comparison of the frequency-selective performance revealed that RAIB is a better option than RACB for mimicking the tonotopy of BM. [ABSTRACT FROM AUTHOR]

Microelectromechanical system (MEMS) test sockets with attached tips were developed for a ball-grid-array integrated circuit (BGA IC) package, using MEMS fabrication technology in conjunction with Ni-Co electroplating and XeF isotropic silicon etching. The electroplating process was used to create metal tips and thick metal cantilevers, which increased the contact reliability and conductivity. XeF isotropic silicon etching was used to release the cantilever array, which reduced the process cost and increased the mechanical stability. A finite element analysis (FEA) simulation was conducted to verify the force-deflection relationships of five types of cantilevers with attached tips. With an input deflection of 40 μm, the measured forces ranged from 12.55 to 26.14 mN, and matched the FEA results. The path resistance between a tip and the appropriate electrode pad was less than 3.49 Ω for all cantilevers when the tips were connected to the corresponding positions with more than 5 mN of contact force. The cantilever design with a length of 430 um and a tip height of 60 um (L430D60) showed the best performance in terms of the force-deflection relationship, a well as resistance. Therefore, the fabricated MEMS test sockets with tips are potentially applicable to actual BGA IC package tests. [ABSTRACT FROM AUTHOR]

Control of small magnetic machines in viscous fluids may enable new medical applications of microrobots. Small-scale viscous environments lead to low Reynolds numbers, and although the flow is linear and steady, the magnetic actuation introduces a dynamic response that is nonlinear. We account for these nonlinearities, and the uncertainties in the dynamic and magnetic properties of the microrobot, by using time-delay estimation. The microrobot consists of a cylindrical magnet, 1 mm long and 500 µm in diameter, and is tracked using a visual feedback system. The microrobot was placed in silicone oil with a dynamic viscosity of 1 Pa.s, and followed step inputs with rise times of 0.45 s, 0.51 s, and 1.77 s, and overshoots of 37.5%, 33.3%, and 34.4% in the x, y, and z directions, respectively. In silicone oil with a viscosity of 3 Pa.s, the rise times were 1.04 s, 0.72 s, and 2.19 s, and the overshoots were 47.8%, 48.5%, and 86.8%. This demonstrates that closed-loop control of the magnetic microrobot was better in the less viscous fluid. [ABSTRACT FROM PUBLISHER]

A new design methodology and fabrication process for two-dimensional (2D) piezoelectric micromachined ultrasonic transducer (pMUT) arrays using a top-crossover-to-bottom (TCTB) structure was developed. Individual sensing and actuation of pMUT elements from a small number of connection lines was enabled by the TCTB structure, and the parasitic coupling capacitance of the array was significantly reduced as a result. A 32 × 32 pMUT array with a TCTB structure was fabricated, resulting in 64 connection lines over an area of 4.8 × 4.8 mm2. The top electrodes for each pMUT element were re-connected by metal bridging after bottom-electrode etching caused them to become disconnected. A deep reactive ion etching process was used to compactify the array. Each pMUT element was a circular-shaped K31-type ultrasonic transducer using a 1 µm thick sol–gel lead zirconate titanate (PZT: Pb1.10 Zr0.52 Ti0.48) thin film. To characterize a single element in the 2D pMUT array, the resonant frequency and coupling coefficient of 20 pMUT elements were averaged to 3.85 MHz and 0.0112, respectively. The maximum measured ultrasound intensity in water, measured at a distance of 4 mm, was 4.6 µW cm−2 from a single pMUT element driven by a 5 Vpp sine wave at 2.22 MHz. Potential applications for development of a TCTB-arranged 2D pMUT array include ultrasonic medical imaging, ultrasonic communication, ultrasonic range-finding and handwriting input systems. [ABSTRACT FROM AUTHOR]

Abstract: We demonstrated a novel MEMS artificial basilar membrane composed of a piezoelectric beam array that mimics the passive frequency selectivity of the cochlea and exhibits acoustic-to-electrical energy conversion. Each beam was designed to have a unique resonance frequency. To determine the resonance frequencies of the beams, the displacement and piezoelectric voltage were measured by applying a periodic chirped signal with a sound pressure level of 109.7dB. The measured resonance frequencies were in the range 10–37kHz. The piezoelectric signal was used to modulate a finite pulse-width signal for electrical stimulation; the pulse widths were in the range 0.43–5.1ms with sound pressure levels in the range 84.9–112.4dB. [Copyright &y& Elsevier]

Animals detect and discriminate countless environmental chemicals for their well-being and survival. Although a single chemical can trigger opposing behavioral responses depending on its concentration, the mechanisms underlying such a concentration-dependent switching remain poorly understood. Here, we show that C. elegans exhibits either attraction or avoidance of the bacteria-derived volatile chemical dimethyl trisulfide (DMTS) depending on its concentration. This behavioral switching is mediated by two different types of chemosensory neurons, both of which express the DMTS-sensitive seven-transmembrane G protein-coupled receptor (GPCR) SRI-14. These two sensory neurons share downstream interneurons that process and translate DMTS signals via distinct glutamate receptors to generate the appropriate behavioral outcome. Thus, our results present one mechanism by which an animal connects two distinct types of chemosensory neurons detecting a common ligand to alternate downstream circuitry, thus efficiently switching between specific behavioral programs based on ligand concentration. [Display omitted] • C. elegans detects the bacteria-derived organic compound DMTS via a SRI-14 GPCR • This single GPCR mediates a DMTS concentration-dependent behavioral switching • SRI-14 is expressed in two different sensory neuron types • Glutamatergic signals mediate DMTS concentration-dependent behavioral switching Choi et al. show that C. elegans detects the volatile bacteria-derived organic compound DMTS via the SRI-14 GPCR, which is both necessary and sufficient to mediate a concentration-dependent behavioral switching in response to DMTS. [ABSTRACT FROM AUTHOR]

The study presented in this paper assessed the frequency selectivity of an artificial basilar membrane (ABM) constructed using a piezoelectric beam array with narrow supports. Three ABM samples were constructed. Each ABM contained 16 beams with various lengths in a one-dimensional array. To experimentally assess the frequency selectivity of the ABM, mechanical vibration induced either by an electrical or an acoustic stimulus was measured with a scanning laser-Doppler vibrometer. The electro-mechanical and acousto-mechanical transfer functions were defined for the same purpose. The tonotopy of each beam array was visualized by post-processing the experimental results. Finite element analyses were conducted to numerically compute the resonance frequencies, identify the associated vibrational modes, and evaluate the harmonic responses of the beams. The influence of the residual stresses existing in the beams was reflected in the geometric models by introducing three different levels of arc-shaped lateral deformations in the beams. The harmonic analyses revealed that each beam of the ABM samples presented independent band-pass characteristics. The experiments and simulations commonly showed a frequency selectivity of the fabricated ABMs in the range of 2-20 kHz. Therefore, the device is suitable for development of a totally implantable artificial cochlea, implementing a mechanical frequency analyzer. This work is part of research to develop a prototype of a totally implantable artificial cochlea. [ABSTRACT FROM AUTHOR]

• A piezoelectric MEMS vector sensor with a cross-shaped beam and a mushroom-shaped mass was fabricated. • The crossed-shaped beam has well deposited piezoelectric thin film. • The directivity of the sensor was mechanically characterized from dipole patterns in x- and y -directions. • Finite element analysis was performed with air and underwater conditions to determine the dipole pattern. [Display omitted] Vector hydrophones based on a micro-electro-mechanical system (MEMS) hold great promise for underwater communications, due to their potential for miniaturization and mass production. Piezoelectric materials have recently been utilized in the fabrication of MEMS-based vector hydrophones, as less power is typically required for their operation. Here, we propose a millimeter-scale piezoelectric MEMS vector sensor with a suspended cross-shaped beam and a mushroom-shaped proof mass configuration. This design was inspired by the bio-transducer of the lateral line of fish. Sensor fabrication involved piezoelectric Pb(Zr 0.52 Ti 0.48)O 3 thin-film deposition by radio-frequency magnetron sputtering onto the beam structure, followed by a multi-etching process and assembly using a three-axis microassembly technique. The fabricated MEMS vector sensor showed a resonance frequency above the working frequency range, which was suitable for naval applications. The directivity of the proposed sensor was determined by dipole patterns in the x and y directions, with a maximum relative sensitivity difference of −42 dB at 1 kHz. Finite element analysis results for the resonance frequency and directivity were in good agreement with the experimental results, suggesting that the proposed vector sensor could be used in underwater communications as a vector hydrophone. [ABSTRACT FROM AUTHOR]

[Display omitted] • Preparation of PVDF-based polymers with quaternary ammonium or quaternary pyridinium groups. • The polymers show the antimicrobial rates of >99.99% against S. aureus , E. coli , and C. albicans. • Polymer blends of small amounts of the polymers (i.e. 1 wt%, 5 wt%) and pristine PVDF. • The blends exhibit enhanced film properties compared with pristine PVDF without phase separation. • The blend films have higher antimicrobial performances and excellent biocompatibility. Poly(vinylidene fluoride) (PVDF) and its copolymers have been extensively utilized owing to their fascinating properties such as thermal stability, chemical resistance, and mechanical robustness. However, their lack of microbial resistance is considered a drawback that limits their adoption as biomedical materials. In this study, to overcome this problem, PVDF-based antimicrobial polymers were prepared by grafting quaternary ammonium or quaternary pyridinium monomers. The polymers could effectively kill gram-positive S. aureus , gram-negative E. coli , and the pathogenic yeast C. albicans (antimicrobial rates > 99.99%). Using the polymer blending method, 1 wt% or 5 wt% of the polymers were added to the pristine PVDF film to provide antimicrobial properties. The blend films exhibited enhanced mechanical properties compared to those of pristine PVDF and notably higher antimicrobial performances (>99% for Blend-Q4VP-5); moreover, they were all biocompatible. [ABSTRACT FROM AUTHOR]

This research focuses on the development of a flexible tactile sensor array consisting of aluminum nitride (AlN) based on micro-electro-mechanical system (MEMS) technology. A total of 2304 tactile sensors were integrated into a small area of 2.5 × 2.5 cm2. Five hundred nm thick AlN film with strong c-axis texture was sputtered on Cr/Au/Cr (50/50/5 nm) layers as the sacrificial layer coated on a Si wafer. To achieve device flexibility, polydimethylsiloxane (PDMS) polymer and SU-8 photoresist layer were used as the supporting layers after etching away a release layer. Twenty-five mM (3-mercaptopropyl) trimethoxysilane (MPTMS) improves the adhesion between metal and polymers due to formation of a self-assembled monolayer (SAM) on the surface of the top electrode. The flexible tactile sensor has 8 × 8 channels and each channel has 36 sensor elements with nine SU-8 bump blocks. The tactile sensor array was demonstrated to be flexible by bending 90 degrees. The tactile sensor array was demonstrated to show clear spatial resolution through detecting the distinct electrical response of each channel under local mechanical stimulus. [ABSTRACT FROM AUTHOR]

Underwater sensors that detect the distance and direction of acoustic sources are critical for surveillance monitoring and target detection in the water. Here, we propose an axial vector sensor that utilizes a small (~1 cm3) compressive-type piezoelectric accelerometer using piezoelectric single crystals. Initially, finite element analysis (FEA) was used to optimize the structure that comprised piezoelectric Pb(Mb1/3Nb2/3)O3-28%PbTiO3 single crystals on a tungsten seismic mass. The receiving voltage sensitivity (RVS) was enhanced through geometric optimization of the thickness and sensing area of the piezoelectric material and the seismic mass. The estimated maximum RVS of the optimized vector sensor was −212 dB. FEA simulations and practical measurements were used to verify the directivity of the vector sensor design, which exhibited a dipole pattern. The dipole beam pattern was used to obtain cardioid patterns using the simulated and measured results for comparison. The results clearly showed the feasibility of using the proposed piezoelectric single-crystal accelerometer for a compressive-type vector sensor. [ABSTRACT FROM AUTHOR]

Summary Experiences during early development can influence neuronal functions and modulate adult behaviors [ 1, 2 ]. However, the molecular mechanisms underlying the long-term behavioral effects of these early experiences are not fully understood. The C. elegans ascr#3 (asc-ΔC9; C9) pheromone triggers avoidance behavior in adult hermaphrodites [ 3–7 ]. Here, we show that hermaphrodites that are briefly exposed to ascr#3 immediately after birth exhibit increased ascr#3-specific avoidance as adults, indicating that ascr#3-experienced animals form a long-lasting memory or imprint of this early ascr#3 exposure [ 8 ]. ascr#3 imprinting is mediated by increased synaptic activity between the ascr#3-sensing ADL neurons and their post-synaptic SMB motor neuron partners via increased expression of the odr-2 glycosylated phosphatidylinositol (GPI)-linked signaling gene in the SMB neurons. Our study suggests that the memory for early ascr#3 experience is imprinted via alteration of activity of a single synaptic connection, which in turn shapes experience-dependent plasticity in adult ascr#3 responses. [ABSTRACT FROM AUTHOR]

We proposed a piezoelectric artificial basilar membrane (ABM) composed of a microelectromechanical system cantilever array. The ABM mimics the tonotopy of the cochlea: frequency selectivity and mechanoelectric transduction. The fabricated ABM exhibits a clear tonotopy in an audible frequency range (2.92-12.6 kHz). Also, an animal model was used to verify the characteristics of the ABM as a front end for potential cochlear implant applications. For this, a signal processor was used to convert the piezoelectric output from the ABM to an electrical stimulus for auditory neurons. The electrical stimulus for auditory neurons was delivered through an implanted intra-cochlear electrode array. The amplitude of the electrical stimulus was modulated in the range of 0.15 to 3.5 V with incoming sound pressure levels (SPL) of 70.1 to 94.8 dB SPL. The electrical stimulus was used to elicit an electrically evoked auditory brainstem response (EABR) from deafened guinea pigs. EABRs were successfully measured and their magnitude increased upon application of acoustic stimuli from 75 to 95 dB SPL. The frequency selectivity of the ABM was estimated by measuring the magnitude of EABRs while applying sound pressure at the resonance and off-resonance frequencies of the corresponding cantilever of the selected channel. In this study, we demonstrated a novel piezoelectric ABM and verified its characteristics by measuring EABRs. [ABSTRACT FROM AUTHOR]