Design and Analyses of a Transdermal Drug Delivery Device (TD3) †.

In this paper, we introduce a novel type of transdermal drug delivery device (TD3) with a micro-electro-mechanical system (MEMS) design using computer-aided design (CAD) techniques as well as computational fluid dynamics (CFD) simulations regarding the fluid interaction inside the device during the actuation process. For the actuation principles of the chamber and microvalve, both thermopneumatic and piezoelectric principles are employed respectively, originating that the design perfectly integrates those principles through two different components, such as a micropump with integrated microvalves and a microneedle array. The TD3 has shown to be capable of delivering a volumetric flow of 2.92 × 10-5 cm3/s with a 6.6 Hz membrane stroke frequency. The device only needs 116 Pa to complete the suction process and 2560 Pa to complete the discharge process. A 38-microneedle array with 450 µm in length fulfills the function of permeating skin, allowing that the fluid reaches the desired destination and avoiding any possible pain during the insertion.

Design of a Novel MEMS Microgripper with Rotatory Electrostatic Comb-Drive Actuators for Biomedical Applications.

Primary tumors of patients can release circulating tumor cells (CTCs) to flow inside of their blood. The CTCs have different mechanical properties in comparison with red and white blood cells, and their detection may be employed to study the efficiency of medical treatments against cancer. We present the design of a novel MEMS microgripper with rotatory electrostatic comb-drive actuators for mechanical properties characterization of cells. The microgripper has a compact structural configuration of four polysilicon layers and a simple performance that control the opening and closing displacements of the microgripper tips. The microgripper has a mobile arm, a fixed arm, two different actuators and two serpentine springs, which are designed based on the SUMMiT V surface micromachining process from Sandia National Laboratories. The proposed microgripper operates at its first rotational resonant frequency and its mobile arm has a controlled displacement of 40 µm at both opening and closing directions using dc and ac bias voltages. Analytical models are developed to predict the stiffness, damping forces and first torsional resonant frequency of the microgripper. In addition, finite element method (FEM) models are obtained to estimate the mechanical behavior of the microgripper. The results of the analytical models agree very well respect to FEM simulations. The microgripper has a first rotational resonant frequency of 463.8 Hz without gripped cell and it can operate up to with maximum dc and ac voltages of 23.4 V and 129.2 V, respectively. Based on the results of the analytical and FEM models about the performance of the proposed microgripper, it could be used as a dispositive for mechanical properties characterization of circulating tumor cells (CTCs).

On the design of a MEMS piezoelectric accelerometer coupled to the middle ear as an implantable sensor for hearing devices.

The presence of external elements is a major limitation of current hearing aids and cochlear implants, as they lead to discomfort and inconvenience. Totally implantable hearing devices have been proposed as a solution to mitigate these constraints, which has led to challenges in designing implantable sensors. This work presents a feasibility analysis of a MEMS piezoelectric accelerometer coupled to the ossicular chain as an alternative sensor. The main requirements of the sensor include small size, low internal noise, low power consumption, and large bandwidth. Different designs of MEMS piezoelectric accelerometers were modeled using Finite Element (FE) method, as well as optimized for high net charge sensitivity. The best design, a 2 × 2 mm2 annular configuration with a 500 nm thick Aluminum Nitride (AlN) layer was selected for fabrication. The prototype was characterized, and its charge sensitivity and spectral acceleration noise were found to be with good agreement to the FE model predictions. Weak coupling between a middle ear FE model and the prototype was considered, resulting in equivalent input noise (EIN) lower than 60 dB sound pressure level between 600 Hz and 10 kHz. These results are an encouraging proof of concept for the development of MEMS piezoelectric accelerometers as implantable sensors for hearing devices.

Recent Advances of MEMS Resonators for Lorentz Force Based Magnetic Field Sensors: Design, Applications and Challenges.

Microelectromechanical systems (MEMS) resonators have allowed the development of magnetic field sensors with potential applications such as biomedicine, automotive industry, navigation systems, space satellites, telecommunications and non-destructive testing. We present a review of recent magnetic field sensors based on MEMS resonators, which operate with Lorentz force. These sensors have a compact structure, wide measurement range, low energy consumption, high sensitivity and suitable performance. The design methodology, simulation tools, damping sources, sensing techniques and future applications of magnetic field sensors are discussed. The design process is fundamental in achieving correct selection of the operation principle, sensing technique, materials, fabrication process and readout systems of the sensors. In addition, the description of the main sensing systems and challenges of the MEMS sensors are discussed. To develop the best devices, researches of their mechanical reliability, vacuum packaging, design optimization and temperature compensation circuits are needed. Future applications will require multifunctional sensors for monitoring several physical parameters (e.g., magnetic field, acceleration, angular ratio, humidity, temperature and gases).

Magnetic, Angular Rate and Gravity Sensor System Fusion for Orientation Estimation.

This paper presents the development of a fusion strategy to integrate and calibrate signals from magnetometers, gyroscopes and accelerometers to implement a magnetic, angular rate and gravity (MARG) sensor system. The aim of such algorithms is to capture signals from the individual sensors and identify, compensate and reduce external and internal errors such as bias, scale factor and drifts, which highly depend on the noise levels. The necessary calibrations to ensure the reliability of captured data are also presented. The orientation data obtained by the proposed algorithm will be compared with a commercial motion capture system, which are currently being used by researchers in biomechanical analysis and in clinical motor rehabilitation studies.

Piezoelectric driving of vibration conveyors: an experimental assessment.

Vibratory feeders or vibratory conveyors have been widely used for the transport and orientation of individual parts and bulk materials in many branches of industrial activity. From the designer's standpoint, the current endeavor is to conceive efficient vibratory feeders, satisfying constraints of power consumption, vibration transmission and noise emission. Moreover, the interest in the reduction of maintenance cost is always present. In this context, this paper investigates experimentally the concept of vibratory conveying based on the use of piezoelectric materials for motion generation. A small-size prototype of a linear conveyor, in which lead-zirconate-titanate (PZT) patches are bonded to the resilient elements, is described. One of the main design goals is that the prototype is intended to be fed directly from the electric network, aiming at avoiding the use of electronic equipment for driving. To comply with this feature and, at the same time, enable to adjust the transport velocity, a mechanical device has been conceived in such a way that the first natural frequency of the conveyor can be changed. It is shown that the transport velocity is determined by the proximity between the excitation frequency and the first natural frequency of the conveyor. The experimental tests performed to characterize the dynamic behavior of the prototype are described and the range of transport velocities is determined.

Synchronization properties of self-sustained mechanical oscillators.

We study, both analytically and numerically, the dynamics of mechanical oscillators kept in motion by a feedback force, which is generated electronically from a signal produced by the oscillators themselves. This kind of self-sustained systems may become standard in the design of frequency-control devices at microscopic scales. Our analysis is thus focused on their synchronization properties under the action of external forces and on the joint dynamics of two to many coupled oscillators. Existence and stability of synchronized motion are assessed in terms of the mechanical properties of individual oscillators, namely, their natural frequencies and damping coefficients, and synchronization frequencies are determined. Similarities and differences with synchronization phenomena in other coupled oscillating systems are emphasized.

Fast frequency sweeping in resonance-tracking SPM for high-resolution AFAM and PFM imaging.

A new resonance-tracking (RT) method using fast frequency sweeping excitation was developed for quantitative scanning probe microscopy (SPM) imaging. This method allows quantitative imaging of elastic properties and ferroelectrical domains with nanoscale resolution at high data acquisition rates. It consists of a commercial AFM system combined with a high-frequency lock-in amplifier, a programmed function generator and a fast data acquisition card. The resonance-tracking method was applied to the atomic force acoustic microscopy (AFAM) and to the piezoresponse force microscopy (PFM) modes. Plots of amplitude versus time and phase versus time for resonant spectra working with different sweeping frequencies were obtained to evaluate the response speed of the lock-in amplifier. It was proved that this resonance-tracking method allows suitable spectral acquisition at a rate of about 5 ms/pixel, which is useful for SPM imaging in a practical scanning time. In order to demonstrate the system performance, images of RT-AFAM for TiN films and RT-PFM for GeTe are shown.

Ferroelectric-carbon nanotube memory devices.

One-dimensional ferroelectric nanostructures, carbon nanotubes (CNT) and CNT-inorganic oxides have recently been studied due to their potential applications for microelectronics. Here, we report coating of a registered array of aligned multi-wall carbon nanotubes (MWCNT) grown on silicon substrates by functional ferroelectric Pb(Zr,Ti)O3 (PZT) which produces structures suitable for commercial prototype memories. Microstructural analysis reveals the crystalline nature of PZT with small nanocrystals aligned in different directions. First-order Raman modes of MWCNT and PZT/MWCNT/n-Si show the high structural quality of CNT before and after PZT deposition at elevated temperature. PZT exists mostly in the monoclinic Cc/Cm phase, which is the origin of the high piezoelectric response in the system. Low-loss square piezoelectric hysteresis obtained for the 3D bottom-up structure confirms the switchability of the device. Current-voltage mapping of the device by conducting atomic force microscopy (c-AFM) indicates very low transient current. Fabrication and functional properties of these hybrid ferroelectric-carbon nanotubes is the first step towards miniaturization for future nanotechnology sensors, actuators, transducers and memory devices.

Mechatronic assistant system for dental drill handling.

BACKGROUND: Holding a dental tool for many hours of work is reflected in fatigue and manual tremor, which causes bad handling of rotatory instruments and consequently injuries within the buccal cavity. At present there exists no system to help the medical dentist in the support and handling of the dental drill. We propose the use of a mechatronic system to help the odontologist in handling the dental drill. METHODS: The mechatronic system consists of an articulated arm with force sensors and actuators that are activated electronically. The mechanism was developed so that the handpiece is held simultaneously by the mechatronic arm and the hand of the dentist. Expert dentists and odontology students were asked to execute tasks to assess positioning accuracy and system resolution. Students performed positioning tasks to evaluate adaptation to the system. The subjects drew the contour of a circle with and without the mechatronic assistant to assess positioning accuracy. Similarly, they made cavities on acrylic typodonts to evaluate resolution and accuracy. Adaptation to the system was evaluated by inserting the drill burr into cavities previously made. RESULTS: The mechatronic system provides support and stability while handling the dental drill. The threshold of force required to move the mechanism prevents involuntary movements affecting the quality of work made on cavities. Positioning accuracy was improved by 53% (p < 0.017) using the system. Similarly, resolution of drilling was improved by 76% (p < 0.001). CONCLUSION: We have developed the first mechatronic system to assist dentists in handling the dental drill. The arm allows the dentist to manipulate the tool with smooth and precise movements during the preparation of dental cavities with the application of force. The mechatronic system minimizes manual tremor due to fatigue and reduces the risk of iatrogenic dental injuries.

A low-cost, portable, micro-controlled device for multi-channel LED visual stimulation.

Light emitting diodes (LEDs) are extensively used as light sources to investigate visual and visually related function and dysfunction. Here, we describe the design of a compact, low-cost, stand-alone LED-based system that enables the configuration, storage and presentation of elaborate visual stimulation paradigms. The core functionality of this system is provided by a microcontroller whose ultra-low power consumption makes it well suited for long lasting battery applications. The effective use of hardware resources is managed by multi-layered architecture software that provides an intuitive and user-friendly interface. In the configuration mode, different stimulation sequences can be created and memorized for ten channels, independently. LED-driving current output can be set either as continuous or pulse modulated, up to 500 Hz, by duty cycle adjustments. In run mode, multiple-channel stimulus sequences are automatically applied according to the pre-programmed protocol. Steady state visual evoked potentials were successfully recorded in five subjects with no visible electromagnetic interferences from the stimulator, demonstrating the efficacy of combining our prototyped equipment with electrophysiological techniques. Finally, we discuss a number of possible improvements for future development of our project.

Real-time monitoring and kinetic parameter estimation of the affinity interaction of jArtinM and rArtinM with peroxidase glycoprotein by the electrogravimetric technique.

ArtinM is a D-mannose binding lectin that has been arousing increasing interest because of its biomedical properties, especially those involving the stimulation of Th1 immune response, which confers protection against intracellular pathogens. The potential pharmaceutical applications of ArtinM have motivated the production of its recombinant form (rArtinM) so that it is important to compare the sugar-binding properties of jArtinM and rArtinM in order to take better advantage of the potential applications of the recombinant lectin. In this work, a biosensor framework based on a Quartz Crystal Microbalance was established with the purpose of making a comparative study of the activity of native and recombinant ArtinM protein. The QCM transducer was strategically functionalized to use a simple model of protein binding kinetics. This approach allowed for the determination of the binding/dissociation kinetics rate and affinity equilibrium constant of both forms of ArtinM with horseradish peroxidase glycoprotein (HRP), a N-glycosylated protein that contains the trimannoside Manα1-3[Manα1-6]Man, which is a known ligand for jArtinM (Jeyaprakash et al., 2004). Monitoring of the real-time binding of rArtinM shows that it was able to bind HRP, leading to an analytical curve similar to that of jArtinM, with statistically equivalent kinetic rates and affinity equilibrium constants for both forms of ArtinM. The lower reactivity of rArtinM with HRP than jArtinM was considered to be due to a difference in the number of Carbohydrate Recognition Domains (CRDs) per molecule of each lectin form rather than to a difference in the energy of binding per CRD of each lectin form.

Analysis of the influence of a mandibular advancement device on sleep and sleep bruxism scores by means of the BiteStrip and the Sleep Assessment Questionnaire.

PURPOSE: A before-and-after experimental clinical study was carried out with the objective of evaluating the effect of a mandibular advancement device (MAD; 75% advancement), made of a thermoplastic material, on sleep bruxism (SB) and sleep scores. MATERIALS AND METHODS: After a habituation period of 1 week, SB scores were taken at baseline and after use of the MAD for 30 days. Scores were compared using the newly developed BiteStrip, which registers the number of contractions of the unilateral masseter muscle after a 5-hour period, giving a severity score from 0 to 3 after the registrations. To assess sleep, the Sleep Assessment Questionnaire (SAQ), a screening tool with scores ranging from 0 to 68, was used before and after use of the MAD. Twenty-eight subjects (13 women, 15 men; mean age: 42.9 +/- 12.0 years) with a clinical history of SB and no spontaneous temporomandibular disorder (TMD) pain were selected. The clinical diagnosis of either moderate or severe SB was further confirmed through use of the BiteStrip (scores 2 or 3) at baseline. A 30-day follow-up period was used for evaluation. Both methods were validated against polysomnography. In addition, common signs and symptoms of TMD based on the Research Diagnostic Criteria for Temporomandibular Disorders were also evaluated before and after use to assess the side effects of the MAD. RESULTS: There was a statistically significant improvement in both SB and sleep scores based on the BiteStrip and the SAQ (Wilcoxon signed rank and Student paired t test, P < .05). In the signs and symptoms of TMD, there was a significant reduction in temporomandibular joint sounds as well as in masseter and temporalis tenderness to palpation. None of the SB subjects experienced any breakage of the MAD. CONCLUSION: The MAD had a positive effect on SB and sleep scores, measured by the BiteStrip and the SAQ, respectively, and did not increase any traditional signs and symptoms of TMD in a 30-day evaluation period.

Using a floating-gate MOS transistor as a transducer in a MEMS gas sensing system.

Floating-gate MOS transistors have been widely used in diverse analog and digital applications. One of these is as a charge sensitive device in sensors for pH measurement in solutions or using gates with metals like Pd or Pt for hydrogen sensing. Efforts are being made to monolithically integrate sensors together with controlling and signal processing electronics using standard technologies. This can be achieved with the demonstrated compatibility between available CMOS technology and MEMS technology. In this paper an in-depth analysis is done regarding the reliability of floating-gate MOS transistors when charge produced by a chemical reaction between metallic oxide thin films with either reducing or oxidizing gases is present. These chemical reactions need temperatures around 200 °C or higher to take place, so thermal insulation of the sensing area must be assured for appropriate operation of the electronics at room temperature. The operation principle of the proposal here presented is confirmed by connecting the gate of a conventional MOS transistor in series with a Fe(2)O(3) layer. It is shown that an electrochemical potential is present on the ferrite layer when reacting with propane.