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Mechanically resonant ferromagnetic MEMS sensors intended for magnetic field gradient measurements are presented. Suspended quad-beams with proof mass have been designed to improve their sensitivity and to simplify the detection. Fabricated devices exhibit the compact size of current MEMS technologies and are built within a simple deep-reactive-ion etching-based process. Nanometer-resolution detection based on optical interferometry and signal processing techniques have been employed to find out dynamic-mode transformation factors of 6.25 × 10−3 T/m/Hz with 0.1-Hz resolution. The device performs in situ gradiometry with a single-sensor structure, which represents a technological advance to current-art gradiometers. Peerreview

A new mathematical model to explain the temperature distribution along the width of current-annealed samples is proposed. The model shows that the heat exchange conditions (radiation and free or forced convection) during annealing can dramatically change the crystallization of the sample. To demonstrate the theoretical results, three Vitroperm® samples were annealed and analyzed magnetically and crystallographically by means of transmission electron microscopy.

The increasing trend of using Commercial of the Shelf components for Aerospace Applications makes Space Agencies open a brand new testing line devoted to the up-screening and characterization in extreme conditions of these "underqualified" components. The up-screening needs to deal with the tasks of degassing, temperature testing and thermal shock, vibration, ageing and stressing, and irradiation of the component under test. In this paper we report on the up-screening process, the previous magnetic characterization and the in-flight resulting data obtained with the magnetic sensors of NANOSAT-01 mission, one and a half years after the launch. The up-screening of the magnetic sensors used in this mission succeed. Their final in-flight qualification is on the road as the behavior of the sensors is nominal. Peerreview

Faraday rotation measurements have been performed on γ-Fe2O3/SiO2 nanocomposite aerogels which are light, porous and transparent magnetic materials. The materials have been prepared by sol–gel polymerization of a silicon alkoxide, impregnation of the intermediate silica gel with a ferrous salt and supercritical drying of the gels. During supercritical evacuation of the solvent, spherical nanoparticles of iron oxide, with a mean particle diameter of 8.1±2.0 nm, are formed and are found to be homogenously distributed within the silica matrix. The specific Faraday rotation of the composite was measured at 0.6 T using polarized light of 810 nm, being 29.6°/cm. The changes in the plane of polarization of the transmitted light and the magnetization of the material present similar magnetic field dependencies and are characteristic of a superparamagnetic system.

We conducted an in vivo experiment to evaluate the resorption rate of a calcium phosphate cement (CPC) with macropores larger than 100 microm, using the CPC called Biocement D (Merck Biomaterial, Darmstadt, Germany), which after setting only shows pores smaller than 1 microm. The gas bubble method used during the setting process created macroporosity. Preset nonporous and porous cement implants were inserted into the trabecular bone of the tibial metaphysis of goats. The size of the preset implants was 6 mm and the diameter of the drill hole was 6.3 mm, leaving a gap of 0.3 mm between implant surface and drill wall. After 2 and 10 weeks, the animals were euthanized and cement implants with surrounding bone were retrieved for histologic evaluation. Light microscopy at 2 weeks revealed that the nonporous implants were surrounded by connective tissue. On the cement surface, we observed a monolayer of multinucleated cells. Ten weeks after implantation, the nonporous implants were still surrounded by connective tissue. However, a thin layer of bone now covered the implant surface. No sign of cement resorption was observed. In contrast, the porous cement evoked a completely different bone response. At 2 weeks, bone formation had already occurred inside the implant porosity. Bone formation even appeared to occur as a result of osteoinduction. Also, at their outer surface, the porous implants were completely surrounded by bone. At 2 weeks, about 31% of the initial cement was resorbed. After 10 weeks, 81% of the initial phosphate cement was resorbed and new bone was deposited. On the basis of these observations, we conclude that the creation of macropores can significantly improve the resorption rate of CPC. This increased degradation is associated with almost complete bone replacement.

Three biphasic materials have been synthesized from a magnetic glass–ceramic (Si-Ca-Fe) and a bioactive sol–gel glass (Si-P-Ca). The ratios of glass–ceramic:sol–gel glass used in this work were 1:1, 2:1, and 5:1. These materials show bioactive and magnetic properties and can be used as thermoseeds for hyperthermia treatment of bone tumors. The sol–gel glass content affects the textural properties of the glass–ceramic, giving rise to porosity, which plays a fundamental role in the formation of an apatite-like layer on the surface. On the other hand, as the sol–gel glass content increases, the magnetic properties change due to the diffusion of Fe ions to the glassy phases of the biphasic materials. The biphasic nature of these materials allows the changing of both properties, depending on the requirements of the patient. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 65A: 71–78, 2003

The bioactive behaviour and drug release of samples composed by sol gel glass with composition 80SiO 2 -16CaO 2 -4P 2 O 5 % mol, polymethylmethacrylate (PMMA) and gentamicine or ibuprofen have been studied. The bioactive behaviour of the samples does not depend on the amount (5% and 10% in weight) or on the type of drug used in this study. In all the cases the SEM micrographs show the formation of a layer that covers the surface of the samples after 24 hours soaked in simulated body fluid (SBF). X ray diffraction patterns show two broad peaks after being soaked 3 days. These peaks could be identified with an apatite-like phase, characteristic in this kind of studies. On the contrary, the release kinetics is strongly dependent on the drug employed. In the case of gentamicine, the curve shows a high slope during the first day soaked in SBF and the complete release occurs before 150 hours. For the ibuprofen samples, the drug release is much slower; the samples containing 10% of ibuprofen do not reach the total release after 600 hours. This different behaviour could be related with the solubility of both drugs in aqueous media.

The influence of hydroxyapatite (OHAp) and gentamicin sulphate (GEN) contents on the release kinetics of GEN, in samples composed of OHAp, poly(methyl methacrylate) (PMMA) and poly(ethyl methacrylate) (PEMA) has been studied. For this purpose, samples with 30 and 40% of OHAp and 5 and 9% of GEN were prepared. The in vitro release study was carried out soaking the samples in simulated body fluid (SBF) at 37 °C for 70 days. The release profiles showed a faster release during the first 10 h, diminishing progressively until the end of the study. It was noticed that the percentage of released GEN increased with the OHAp content. For samples with 40% of OHAp, GEN release is nearly independent of the initial amount of such drug (in the range 5–9%), whereas for samples with 30% of OHAp, the release process is favoured by higher contents of GEN, which would favour a higher SBF uptake. GEN release is related to SBF uptake, which is in turn related, on the one hand, to the OHAp content (increase of the porosity and the hydrophilic character of the samples) and on the other hand, to content of GEN.

A novel biphasic material has been synthetised from a sol–gel-derived glass (Si–Ca–P) and a glass–ceramic obtained from a melt-derived glass (Si–Ca–Fe). Both components of such a biphasic mixture are bioactive, but with different kinetics for the growth of an apatite-like layer on the surface of these materials, needing only one day for the sol–gel-derived glass and one month for the glass–ceramic. The glass–ceramic shows magnetic properties. The biphasic material, obtained from a mixture 1:1 of these components, is bioactive, and its surface is coated after 15 days of soaking in SBF. The biphasic material also exhibited magnetic behaviour, useful for hyperthermia.

A magnetic glass-ceramic suitable to be used as biomaterial has been synthesized. After the NaO-Fe 2 O 3 -CaO-SiO 2 starting glass is annealed, a glass-ceramic based on ferroan wollastonite-like and ∈-(Fe,Ca)SiO 3 -like phases is obtained. Both phases contain Fe 2+ ions, leading to two magnetic phases with different coercive forces. Because of the magnetic properties, this material could be used as a thermoseed for cancer treatment by hyperthermia. This glass-ceramic is coated by an amorphous layer when it is soaked in simulated body fluid (SBF). This new layer, formed with the incorporation of phosphorus over the surface, would lead to a good integration with the bone tissue after being implanted.

A new application of MCM-41 mesoporous materials has been developed. Two kinds of surfactants, C16TAB and C12TAB, have been employed to get different pore sizes. The samples were disk-shaped conformed before and after charging with ibuprofen, an anti-inflammatory drug. In all the cases the weight percent ratio of drug/MCM-41 was 30%. The drug release plots show a different behavior depending on the method for charging the drug in the material but not on the employed surfactant.

In this work the release kinetics of gentamicin sulfate (GEN) in samples composed by hydroxyapatite, poly(methyl methacrylate), and poly(ethyl methacrylate) has been studied. The release study was performed by soaking three samples in simulated body fluid at 37°C; the medium was periodically replaced during 70 days. The concentration of GEN was determined by the o-phtaldialdehyde method. The release profile shows three stages: the first stage, occurring during the first 10 h, corresponds to a fast release (nearly 30% of the drug is released in this period). The second stage is slower and includes from the first 10 h to 16 days, releasing 60% of the total amount of GEN. The final stage is the slowest and it takes from 16 to 70 days (10% of GEN is released). The fraction of released GEN versus square root of time can be fitted to a third order polynomial, corresponding with the model proposed by Cobby et al. (J Pharm Sci 1974;63:725–732). The characterization of the samples after the release study shows that a carbonate hydroxyapatite layer has grown on the whole surface of the composites. © 2000 John Wiley & Sons, Inc. J Biomed Mater Res, 52, 1–7, 2000.

The influence of the domain wall thickness on eddy current losses has been calculated. It is shown that, for samples with low magnetic anisotropy and small thickness, the reduction of magnetic losses with respect to the zero thickness domain wall must be seriously taken into account.

In this work the influence of a sputtered coating (SiO 2 ) on a FeSiCuNbB amorphous alloy has been studied from two points of view: the effect on the nanocrystallization process and the effect on the magnetic properties. It is shown that after heat treatment (550°C for 1 h) a magnetic anisotropy normal to the ribbon axis appears due to anelastic strains.

A magnetic glass-ceramic suitable to be used as biomaterial has been synthesized. After the NaO-Fe 2 O 3 -CaO-SiO 2 starting glass is annealed, a glass-ceramic based on ferroan wollastonite-like and ∈-(Fe,Ca)SiO 3 -like phases is obtained. Both phases contain Fe 2+ ions, leading to two magnetic phases with different coercive forces. Because of the magnetic properties, this material could be used as a thermoseed for cancer treatment by hyperthermia. This glass-ceramic is coated by an amorphous layer when it is soaked in simulated body fluid (SBF). This new layer, formed with the incorporation of phosphorus over the surface, would lead to a good integration with the bone tissue after being implanted.

A focused-ion-beam-assisted technique intended for ultrasmall, hard-magnet fabrication has been developed. By means of ion-beam-induced milling and deposition, reduced-size NdFeB magnets were extracted from a macroscopic quarry and bonded to the surface of a thin-film bulk acoustic resonator (FBAR). Electrical characterization of the FBAR before and after bonding of the magnet was carried out, thus observing both a downshifting of the resonance frequency and a reduction of the quality factor of the resonator. The magnetic behavior of the nanomagnet has been confirmed by means of magnetometry measurements based on atomic force microscopy. Peerreview

The dynamic properties of membranes have been object of many researches since they can be used as sensor heads in different devices. Some methods have been proposed to solve the problem of determining the resonance frequencies and their dependence on the stress caused by forces applied on the membrane surface. The problem of the vibrating rectangular membrane under a stress caused by a uniform in-plane force is well known. However, the resonance frequency behaviour when the force is out-of-plane instead of in-plane, is not so well understood and documented. A gradiometer which uses a silicon square membrane with a magnet fixed on it as a sensor head has been developed in a previous work. This device reports a quadratic dependence of the frequency on the out-of-plane magnetic force. In this work, simulations to obtain the dependence of the frequency of the fundamental flexural mode on the stress have been performed. It has been studied the influence of in-plane and out-of-plane forces applied to the membrane. As expected, a square root dependence has been found for in-plane forces. Nevertheless, the problem is more complex when out-of plane forces are considered. Out-of-plane forces gives rise to an initial quadratic dependence which turns into a square root dependence from a certain stress value. The quadratic range increases and the rate of change of the frequency decreases as the surface of the magnet fixed on the membrane increases. The study has addressed these problems and both, experimental and simulated results have been compared and a good agreement between experimental and simulated results has been found, 14 pages, 10 figures

Two MEMS structures—a cantilever beam and a quad-beam—have been designed and fabricated through a three-step deep reactive ion etching (DRIE) process. Devices feature target patterns to align with an external optical detection system and a micromachined cavity to embed an NdFeB hard mini-magnet, thus releasing the stress of structures. Structures are intended for magnetostatic gradient measurements. Induced magnetic fields generate an attracting force on the magnet that deflects the sensor. Deflection is optically detected through nanometer-resolution confocal microscopy. The static-mode sensitivity of up to 1.86 × 10−4 T m−1 demonstrates that MEMS gradiometers are able to perform in situ gradiometry with a single sensor and miniaturized size. Suitable techniques for integrated detection are discussed. Peerreview

We report a focused-ion-beam-assisted technique intended for ultra-small, hard magnet fabrication and placement on thin-film bulk acoustic resonators (FBAR). Reduced-size NdFeB magnets were extracted from a macroscopic quarry and bonded to the surface of FBARs by ion-beam-induced milling and deposition. Experimental measurements confirm the success of the method. S-parameter extraction was performed before and after nanomagnet attachment. Preliminary finite-element analysis has predicted force sensitivity at fundamental frequencies (kHz-MHz).

On December 2004, the Spanish Space Agency INTA (Instituto Nacional de Técnica Aeroespacial) launched the first nanosatellite called NANOSAT (Fig. 1) on board an European rocket Ariane 5, from the French Guyana. The satellite consists of a hexagonal device of

A new simple and sensitive dilatometer to measure magnetostriction of ribbons has been developed, based on an optical fiber sensor using an annular photodiode. The optical fiber is used bidirectionally, both for emission and detection of light, simplifying the access to the ribbon under test. The working principle is based on the measurement by reflection of the longitudinal displacement of the ribbon end. For a Vitroperm amorphous ribbon of 100 mm length, 21 microm thickness, and 8.3 mm width, a displacement of 2.571 microm with a maximum uncertainty of 8 nm has been obtained.

Measurements of the field dependence of Young's modulus (/spl Delta/E effect) are reported for amorphous ribbons of Fe/sub 73.5/Cu/sub 1/Nb/sub 3/Si/sub 16.5/B/sub 6/ annealed for 1 hour at temperatures of 450/spl deg/C, 520/spl deg/C, 540/spl deg/C and 620/spl deg/C. The magnitude of the effect varies from 36% to less than 10/sup -5/ as the magnetostriction constant /spl lambda//sub s/ is reduced by nanocrystallization. The results are discussed in the light of existing models, and suggest that the anisotropy is the result of competition between stress, magnetocrystalline and shape contributions.

In this work the influence of nanocrystalline structure on magnetic losses is pointed out. Annealed samples, with and without SiO/sub 2/ coating, show mainly hysteretic losses. Eddy current losses are more important in the as cast state than in the other cases. These measurements suggest that the occurrence of the nanocrystalline structure modifies the wall kinetics and so the contribution of eddy current losses in comparison with the amorphous state. >

Item does not contain fulltext A new way to create macropores in calcium phosphate cements has been developed. The method consists in adding NaHCO3 to the starting cement powder (Biocement D) and using two different liquids: first a basic liquid to form the paste and later an acid liquid to obtain CO2 bubbles. Mercury intrusion measurements showed a dramatic increase both in macropores with an average size of 100 m and in the total porosity (even higher than 50% with respect to the Biocement D). This method does not change in any significant way the final reaction products of the starting material after being soaked 3 days in Ringer solution. Only, due to the increase of the porosity. the compressive strength of the porous cement decreases significantly.

El objetivo de este trabajo fue estudiar la influencia del contenido de hidroxiapatita (OHAp) y de sulfato de gentamicina (SG) en la velocidad de liberación de dicho antibiótico a partir de materiales compuestos por OHAp, polimetacrilato de metilo (PMMA) y polimetacrilato de etilo (PEMA). Para ello se prepararon muestras con diferente proporción de OHAp (30 y 40%) y de SG (5 y 10%). El estudio de liberación se llevó a cabo sumergiendo 3 muestras de cada grupo en SBF a 37°C, el medio fue renovado a diferentes intervalos de tiempo durante 70 días. La concentración de gentamicina fue determinada por el método del o-ftaldialdehído. Los resultados del estudio de liberación mostraron, que la liberación ocurre de manera más rápida durante las primeras 10 horas de inmersión en SBF y que posteriormente se hace más lenta. Se observó que las muestras con un mayor tanto por ciento (40%) de OHAp liberan mayor cantidad de antibiótico. Las muestras con un 40% de OHAp liberaron el 100% de SG a los 70 días, mientras que en ese mismo período las muestras con 30% de OHAp liberaron un 85%. Por otra parte, se observó que la cantidad de gentamicina añadida inicialmente no afecta el tanto por ciento de SG que se libera.

A magnetic field sensor is presented which is based on the inverse Wiedemann effect (IWE) on amorphous wires. The external magnetic DC field to be detected changes the time symmetry of the output voltage induced in a pick-up coil, creating even harmonics. Measurement results show important advantages in sensitivity and working frequencies mainly due to the core's geometry. The sensor has outstanding sensitivity for magnetic fields below 0.02 mT, as well as a low working frequency and current intensity. >

Crystallization of Vitroperm® alloy has been realized by means of Joule heating. The influence of the gas flow around the sample during the heat treatment is dramatic and it produces an inhomogeneous crystallization. For large enough gas flow the temperature of the sample surroundings can be considered constant and a temperature gradient appears over the sample width, which means a gradient in size and concentration of Fe–Si and Fe–B nanocrystals. For adequate gas flow values the temperature of the sample edges is below the Fe–B crystallization value whereas the centre is above that value, showing therefore completely different magnetic behaviour.