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New multi-stimuli responsive materials are required in smart systems applications to overcome current limitations in remote actuation and to achieve versatile operation in inaccessible environments. The incorporation of detection mechanisms to quantify in real time the response to external stimuli is crucial for the development of automated systems. Here, we present the first wireless opto-magnetic actuator with mechanochromic response. The device, based on a nanostructured-iron (Fe) layer transferred onto suspended elastomer structures with a periodically corrugated backside, can be actuated both optically (in a broadband spectral range) and magnetically. The combined opto-magnetic stimulus can accurately modulate the mechanical response (strength and direction) of the device. The structural coloration generated at the corrugated back surface enables to easily map and quantify, in 2D, the mechanical deflections by analyzing in real time the hue changes of images taken using a conventional RGB smartphone camera, with a precision of 0.05°. We demonstrate the independent and synergetic optical and magnetic actuation and detection with a detection limit of 1.8 mW·cm-2 and 0.34 mT, respectively. The simple operation, versatility, and cost-effectiveness of the wireless multiactuated device with highly sensitive mechanochromic mapping paves the way to a new generation of wirelessly controlled smart systems., We acknowledge funding from the Generalitat de Catalunya through the 2017-SGR-292 project. The funding from the Spanish Ministerio de Ciencia, Innovación y Universidades (MICINN) through the PID2019-106229RB-I00, MAT2016-77391-R, PCIN2016-093 (M-ERA-NET), DPI2015-68197-R, and RTI2018-096786-B-I00 projects and the Ramon y Cajal Fellowship (RyC2013-14479) is acknowledged. The PhD fellowship CIBAE-023-2014 (from SENESCYT) is also acknowledged. ICN2 is funded by the CERCA programme/Generalitat de Catalunya. The ICN2 is supported by the Severo Ochoa Centres of Excellence programme, funded by the Spanish Research Agency (AEI, grant no. SEV-2017-0706).

Tissue barriers play a crucial role in human physiology by establishing tissue compartmentalization and regulating organ homeostasis. At the interface between the extracellular matrix (ECM) and flowing fluids, epithelial and endothelial barriers are responsible for solute and gas exchange. In the past decade, microfluidic technologies and organ-on-chip devices became popular as in vitro models able to recapitulate these biological barriers. However, in conventional microfluidic devices, cell barriers are primarily grown on hard polymeric membranes within polydimethylsiloxane (PDMS) channels that do not mimic the cell-ECM interactions nor allow the incorporation of other cellular compartments such as stromal tissue or vascular structures. To develop models that accurately account for the different cellular and acellular compartments of tissue barriers, researchers have integrated hydrogels into microfluidic setups for tissue barrier-on-chips, either as cell substrates inside the chip, or as self-contained devices. These biomaterials provide the soft mechanical properties of tissue barriers and allow the embedding of stromal cells. Combining hydrogels with microfluidics technology provides unique opportunities to better recreate in vitro the tissue barrier models including the cellular components and the functionality of the in vivo tissues. Such platforms have the potential of greatly improving the predictive capacities of the in vitro systems in applications such as drug development, or disease modeling. Nevertheless, their development is not without challenges in their microfabrication. In this review, we will discuss the recent advances driving the fabrication of hydrogel microfluidic platforms and their applications in multiple tissue barrier models.

Altres ajuts: ICN2 is funded by the CERCA programme/Generalitat de Catalunya. Ultrabroadband light absorbers are attracting increasing interest for applications in energy harvesting, photodetection, self-regulated devices or soft robotics. However, current absorbers show detrimental insufficient absorption spectral range, or light angle and polarization dependence. Here we show that the unexplored optical properties of highly-damped plasmonic materials combined with the infrared absorption of thin polymer films enable developing ultrabroadband light-absorbing soft metamaterials. The developed metamaterial, composed of a nanostructured Fe layer mechanically coupled to a thin polydimethylsiloxane (PDMS) film, shows unprecedented ultrabroadband and angle-independent optical absorption (averaging 84% within 300-18000 nm). The excellent photothermal efficiency and large thermal-expansion mismatch of the metamaterial is efficiently transformed into large mechanical deflections, which we exploit to show an artificial iris that self-regulates the transmitted light power from the ultraviolet to the long-wave infrared, an untethered light-controlled mechanical gripper and a light-triggered electrical switch.

We demonstrate an integrated optical pressure sensing platform for multiplexed optofluidics applications. The sensing platform consists in an array of elastomeric on-side nanostructured membranes -effectively 2D photonic crystal- which present colour shifts in response to mechanical stress that alter their nanostructure characteristical dimensions, pitch or orientation. The photonic membranes are prepared by a simple and cost-effective method based on the infiltration of a 2D colloidal photonic crystal (CPC) with PDMS and their integration with a microfluidic system. We explore the changes in the white light diffraction produced by the nanostructured membranes when varying the pneumatic pressure in the microfluidics channels as a way to achieve a power-free array of pressure sensors that change their reflective colour depending on the bending produced on each sensor. The structural characterization of these membranes was performed by SEM, while the optical properties and the pressure-colour relation were evaluated via UV-Vis reflection spectrometry. Maximum sensitivities of 0.17 kPa−1 is obtained when measuring at Littrow configuration (θin = −θout), and close to the border of the membranes. The reflected colour change with pressure is as well monitorized by using a smartphone camera.

We present the fabrication of nanomechanical surface stress based transducers by using the nowadays knowns as smart materials, to achieve a power-free array of sensors that change their reflective color depending on the surface stress change induced on each sensor. Nanocomposite materials of elastomeric polymers and ordered nanoparticles embedded inside the polymer were chosen for the fabrication process. These composite materials, besides being cheap and easily fabricated in mass production, present a mechanochromic behavior producing a color change of the material when applying a deformation process mainly due to the change in the distance between nanoparticles. We have fabricated arrays of mechanochromic membranes by infiltrating colloidal photonic crystals of polystyrene nanoparticles with Polydimethylsiloxane (PDMS). Hybrids PDMS and 3D or 2D colloidal photonic crystals were prepared, and compared its sensitivity to strain changes. The color, due to the Bragg diffraction (3D) or light scattering (2D), was analyzed by UV-visible spectrometry.

This paper reports on the design, fabrication, and evaluation of a mass density and viscosity sensor based on an array of polysilicon microbeam resonators integrated with 20 pL fluidic microchannels. When filled with water, resonators exhibit resonant frequencies close to 500 KHz and Q-factor values of 400 operating at atmospheric pressure and ambient temperature. Real-time measurements are highly reproducible and only require 250 μL of the sample fluid. The builtin interferometric readout enables automatic detection of the beams increasing the throughput analysis and reducing detection times. The frequency shift response shows a linear behavior in accordance with the density of evaluated solvents, organic solutions, and alcoholic drinks, reporting a mass responsivity of 7.4 Hz/pg. Also, the sensor is capable of measuring the viscosity of liquid phase samples with a resolution of 0.15 cP by tracking the Q-factor response of the sensor within a linear regime between 1 to 2.6 cP. This approach demonstrates the ability to identify in real-time changes of fluids in the liquid phase that could provide a valuable assessment for bioanalytical applications., This work was supported in part by the National Council for Science and Technology (CONACyT-Mexico) and also with the Integrated Clean Room for Micro and Nano Fabrication of the Centro Nacional de Microelectróica - Instituto de Microelectrónica de Barcelona (ICTS IMB-CNM); in part by the Departament d’Universitats, Recerca i Societat de la Informació de la Generalitat de Catalunya, under Grant 2014SGR624; and in part by the Severo Ochoa Centers of Excellence Program of Spanish MINECO under Grant SEV-2013-0295.

We demonstrate the possibility of producing regular, long-range, spatially ordered polymer patterns without requiring the use of physical or chemical templating through the interfacial destabilization of a thin polymer film driven by surface acoustic waves (SAWs). The periodicity and spot size of the pattern are observed to be dependent on a single parameter, that is, the SAW frequency (or wavelength), therefore offering a rapid, simple, yet novel method for self-organized regular spatial polymer pattern formation that is far more tunable than conventional polymer patterning procedures.

We have studied the optomechanical performance of optical microcantilevers fabricated with integrated waveguides for the on-chip and real-time detection of biorecognition events. The nanomechanical photonic device consists of an optical microcantilever with on-chip integrated waveguides for both coupling the light and detecting the microcantilever response. The photonic device was designed to reach a high sensitivity with a low deflection noise density (DND) of only 0.13fm/√ Hz. The BioMEMS transducer is embedded into a proper designed PMMA/PDMS microfluidic header and connected to a flow delivery system to study the response of the fully-integrated device under physiological conditions. As a proof of concept, we have studied the photonic microcantilever bending during consecutive formation of ultrathin polyelectrolyte multilayer films (electrostatic binding) and during biofunctionalization and biorecognition of the human growth hormone. The read-out platform was developed based on a single laser-single acquisition channel. To avoid the effect of external factors such as device positioning or temperature fluctuations, an automatized light coupling system keeps on tracking the laser beam focused into an input waveguide, increasing the required reproducibility needed for BioMEMS devices and paving the way for a potential portable multichannel sensor platform., Authors acknowledge the financial support of the Generalitat de Catalunya and has support from the Departament d’Universitats, Recerca i Societat de la Informació de la Generalitat de Catalunya (2014 SGR 624), ICN2 is the recipient of Grant SEV-2013-0295 from the “Severo Ochoa Centers of Excellence” Program of Spanish MINECO. The surface blocking process was performed by the ICTS “NANBIOSIS”, more specifically by the microdeposition unit (NanoeNablerTM system from BioForce Nanosciences, USA), unit of the CIBER in Bioengineering, Biomaterials & Nanomedicne (CIBER-BBN).

In this work we describe the use of a micro-scale array of polysilicon doubly clamped beams, based on the approach of embedding microfluidic channels inside the resonators, as an innovative platform for multiplexed biosensors. Finite element methods in COMSOL were employed to simulate the structural mechanical behavior and to know the conditions to determine the frequency response in order to achieve optimal sensitivities and quality factors. Particularly, we studied the effect of microchannel cross-section area, length and sidewall thickness respect to the microchannel dimensions with the objective of injecting solutions of different densities. By integrating additional multiphysics models we analyzed the governing microfluidics, and we estimated that a maximum pressure difference of 7 MPa along the microchannels is required to establish an optimum water flow rate of 0.1 μl/min, which is adequate for biosensor applications. To validate the simulations we compared the thermal noise response of a fabricated array of microbridges in air, and we obtained resonant frequencies between 700 KHz and 1 MHz, in good agreement with our simulated results but with downward frequency shifts due to the undercut effect after fabrication.

7 páginas, 5 figuras., We present a new technique to increase the quality factor of micro-nanomechanicl oscillators using digital electronics. The mechanical oscillator is set into oscillation by using a single driving force whose amplitude depends on the amplitude and phase shift of the oscillation. Experiments performed with microcantilevers in air and aqueous solution show that the quality factor can be increased about two orders of magnitude. This technique is applied for the measurement of the viscosity change of an aqueous solution due to the presence of proteins., This work was supported by MyCT (BIO2001-1235-C03-01).

The achievement of high sensitivity and highly integrated transducers is one of the main challenges in the development of high-throughput biosensors. The aim of this study is to improve the final sensitivity of an opto-mechanical device to be used as a reliable biosensor. We report the analysis of the mechanical and optical properties of optical waveguide microcantilever transducers, and their dependency on device design and dimensions. The selected layout (geometry) based on two butt-coupled misaligned waveguides displays better sensitivities than an aligned one. With this configuration, we find that an optimal microcantilever thickness range between 150 nm and 400 nm would increase both microcantilever bending during the biorecognition process and increase optical sensitivity to 4.8 × 10−2 nm−1, an order of magnitude higher than other similar opto-mechanical devices. Moreover, the analysis shows that a single mode behaviour of the propagating radiation is required to avoid modal interference that could misinterpret the readout signal., The authors acknowledge the financial support of Generalitat de Catalunya (2014/SGR/624) and CIBER-BBN and ICN2. CIBER-BBN is an initiative funded by the VI National R&D&i Plan 2008–2011, Iniciativa Ingenio 2010, Consolider Program, CIBER Actions and financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund. ICN2 is the recipient of Grant SEV-2013- 0295 from the ‘Severo Ochoa Centers of Excellence’ Program of Spanish MINECO.

We have developed a set of working modes for scanning probe microscopy?(SPM), which generalizes the usual method of acquiring data. We call these modes three-dimensional?(3D) modes. Using these modes it is possible to measure typical SPM magnitudes, such as, for example, the tunnel current, the normal force and the amplitude or frequency of the cantilever oscillation, as a function of any other two magnitudes of the system: f(x1,x2). In this paper we present different examples of 3D modes. In particular, we have applied 3D modes to the study of the electrostatic interaction of co-adsorbed single walled carbon nanotubes and individual DNA molecules with a metallic scanning force microscopy tip. The data indicate that adsorbed DNA has a dielectric constant similar to that of the glass substrate.

In this work we analyze and characterize a suspended polysilicion double-clamped beam array as an innovative platform for biosensing applications based on the high sensitivity of micromechanical resonators. The thermal noise response of the array of hollow microbridge resonators (HMB) was sequentially detected by means of a custom scanning optical free space interferometer. The results demonstrated that the microbridges operate at resonant frequencies around 850 KHz with quality factors and spring constants up to 280 and 3514 N/m, respectively. Furthermore, when filled with distilled water, no significant changes in the quality factor were noticeable and the spectral measurements depicted a frequency shift of 20 KHz. We contend that the HMB integrated system is capable of sensing different species based on the spectral frequency response of the overall array of resonators.

We have developed a hybrid platform that combines two well-known biosensing technologies based on quite different transducer principles: surface plasmon resonance and nanomechanical sensing. The new system allows the simultaneous and real-time detection of two independent parameters, refractive index change (Δn), and surface stress change (Δσ) when a biomolecular interaction takes place. Both parameters have a direct relation with the mass coverage of the sensor surface. The core of the platform is a common fluid cell, where the solution arrives to both sensor areas at the same time and under the same conditions (temperature, velocity, diffusion, etc.).The main objective of this integration is to achieve a better understanding of the physical behaviour of the transducers during sensing, increasing the information obtained in real time in one single experiment. The potential of the hybrid platform is demonstrated by the detection of DNA hybridization. © 2013 American Institute of Physics., Authors acknowledge the financial support from Juan de la Cierva Program (MICINN-JDC) and Fundación M. Botín.

Reliable immobilization of bioreceptors over any sensor surface is the most crucial step for achieving high performance, selective and sensitive biosensor devices able to analyze human samples without the need of previous processing. With this aim, we have implemented an optimized scheme to covalently biofunctionalize the sensor area of a novel nanophotonic interferometric biosensor. The proposed method is based on the ex-situ silanization of the silicon nitride transducer surface by the use of a carboxyl water soluble silane, the carboxyethylsilanetriol sodium salt (CTES). The use of an organosilane stable in water entails advantages in comparison with usual trialkoxysilanes such as avoiding the generation of organic waste and leading to the assembly of compact monolayers due to the high dielectric constant of water. Additionally, cross-linking is prevented when the conditions (e.g. immersion time, concentration of silane) are optimized. This covalent strategy is followed by the bioreceptor linkage on the sensor area surface using two different approaches: an in-flow patterning and a microcontact printing using a biodeposition system. The performance of the different bioreceptor layers assembled is compared by the real-time and label-free immunosensing of the proteins BSA/mAb BSA, employed as a model molecular pair. Although the results demonstrated that both strategies provide the biosensor with a stable biological interface, the performance of the bioreceptor layer assembled by microcontact printing slightly improves the biosensing capabilities of the photonic biosensor. © 2012 Elsevier Inc., Authors acknowledge financial support from M. Botín foundation., Funded by: Fundación M. Botín; Spanish Ministry of Industry. Grant Number: SENA project (TSI-020301-2008-11); Spanish Ministry of Science and Innovation. Grant Number: Juan de la Cierva Program (MICINN-JDC).

We describe the fabrication of a surface acoustic wave (SAW) atomizer and show its ability to generate monodisperse aerosols and particles for drug delivery applications. In particular, we demonstrate the generation of insulin liquid aerosols for pulmonary delivery and solid protein nanoparticles for transdermal and gastrointestinal delivery routes using 20 MHz SAW devices. Insulin droplets around 3 µm were obtained, matching the optimum range for maximizing absorption in the alveolar region. A new approach is provided to explain these atomized droplet diameters by returning to fundamental physical analysis and considering viscous-capillary and inertial-capillary force balance rather than employing modifications to the Kelvin equation under the assumption of parametric forcing that has been extended to these frequencies in past investigations. In addition, we consider possible mechanisms by which the droplet ejections take place with the aid of high-speed flow visualization. Finally, we show that nanoscale protein particles (50‐100 nm in diameter) were obtained through an evaporative process of the initial aerosol, the final size of which could be controlled merely by modifying the initial protein concentration. These results illustrate the feasibility of using SAW as a novel method for rapidly producing particles and droplets with a controlled and narrow size distribution.

24 páginas.-- II Parte; Optical Biosensors: Tomorrow.-- Frances S. Ligler y Chris Rowe Taitt (eds.).-- 2ª Edición.

21 páginas.-- Avraham Rasooly, Keith E. Herold (eds.), Microcantilevers based-biosensors are a new label-free technique that allows the direct detection of biomolecular interactions in a label-less way and with great accuracy by translating the biointeraction into a nanomechanical motion. Low cost and reliable standard silicon technologies are widely used for the fabrication of cantilevers with well-controlled mechanical properties. Over the last years, the number of applications of these sensors has shown a fast growth in diverse fields, such as genomic or proteomic, because of the biosensor flexibility, the low sample consumption, and the non-pretreated samples required. In this chapter, we report a dedicated design and a fabrication process of highly sensitive microcantilever silicon sensors. We will describe as well an application of the device in the environmental field showing the immunodetection of an organic toxic pesticide as an example. The cantilever biofunctionalization process and the subsequent pesticide determination are detected in real time by monitoring the nanometer-scale bending of the microcantilever due to a differential surface stress generated between both surfaces of the device.

9 páginas, 13 figuras, 1 tabla.-- PDF pre-print.-- et al., Microcantilever-based biosensors are a promising tool to detect biomolecular interactions in a direct way with high accuracy. We show the development of a portable biosensor microsystem able to detect nucleic acid hybridization with high sensitivity. The microsystem comprises an array of 20 micromechanical cantilevers produced in silicon technology, a polymer microfluidic system for delivery of the samples, an array of 20 vertical cavity surface emitting lasers (VCSELs) with collimated beams thanks to an integrated microlens array, an optical coupling element to provide the optical path required, and chips with the photodetectors and the CMOS circuitry for signal acquisition and conditioning, capable of measuring the cantilever deflection with sub-nanometer resolution. Robust immobilization and regeneration procedures have been implemented for the oligonucleotide receptor sequences. In a further innovation, an optical waveguide cantilever transducer has been also developed in order to improve the final performance of the device. This has a number of advantages in terms of a simple optical geometry and improved sensitivity., This work is being supported by the EU Contract IST-2001-37239. Spanish authors are also supported by national project TIC2002-10473-E.

3 páginas, 2 figuras, 1 tabla., The authors have designed and fabricated arrays of microcantilevers with a geometry that shows reduced initial angular offset and angle deviation between the cantilevers of the array. This feature allows to detect the displacement of the cantilevers using the optical beam deflection technique and a single split photodetector. The structure is analytically and numerically simulated to demonstrate its feasibility. In addition, experimental measurements of the angle offset corroborate the offset and the angle deviation reduction. Finally, they illustrate the potential of these micromechanical structures as sensors by measuring a monolayer of single stranded DNA.

An optical readout technique has been developed for real-time monitoring of the profile of microcantilever arrays for sensing applications. The technique is based on the automated two-dimensional scanning of a laser beam by using voice-coil actuators. Cantilever profiles are obtained with subnanometer resolution and a processing speed of about ten cantilevers per second. The technique is applied for real-time monitoring of the adsorption of the alkylthiol mercaptohexanol in an aqueous environment by using an array of five microcantilevers. Molecular adsorption produces a cantilever strain that significantly differs from the Stoney's model. Main strain changes are strongly located near the cantilever clamping., The authors would like to acknowledge A. Calle, L. Lechuga, and M. Calleja for their helpful suggestions. This work was supported by Spanish Ministry of Science (GEN2001-4856-C13-11).

A technique for the readout of the nanomechanical response of multiple microcantilevers is presented. This combines the optical beam deflection technique and the scanning of a laser beam illuminating the cantilevers of an array sequentially. The individual motion of each microcantilever is obtained by correlating the total photocurrent collected in a photodetector array, the position of the laser beam and the coordinates of the laser spot centroid on the photodetector. The technique provides sub-angstrom resolution in the cantilever deflection and it allows the readout of tens of cantilevers per second. This is applied for the quasi-simultaneous detection of single-stranded DNA with an array of five microcantilevers. Moreover, this technique also allows the measurement of the resonant frequency of individual microcantilevers into an array. This can be applied for multiple detection of several pathogen targets. © 2004 Elsevier B.V. All rights reserved.

8 páginas, 5 figuras, 1 tabla.-- PACS: 87.80.−y; 87.17.Gg; 07.10.Cm; 87.83.+a, We present a technology for the fabrication of cantilever arrays aimed to develop an integrated biosensor micro-system. The fabrication process is based on spin coating of the photosensitive polymer and near-ultraviolet exposure. Arrays of up to 33 microcantilevers are fabricated in the novel polymer material SU-8. The low Young’s modulus of the polymer, 40 times lower than that of silicon, enables to improve the sensitivity of the sensor device for target detection. The mechanical properties of SU-8 cantilevers, such as spring constant, resonant frequency and quality factor are characterized as a function of the dimensions and the medium. The devices have been tested for measurement of the adsorption of single stranded DNA and subsequent interstitial adsorption of lateral spacer molecules. We demonstrate that sensitivity is enhanced by a factor of six compared to that of commercial silicon nitride cantilevers., The authors acknowledge P. Rasmussen and L. G. Carrascosa for fruitful discussion. M. C. acknowledges financial support from I3P-CSIC and MERG-CT-2004-510638. J. T. and M. A. acknowledge financial support from MCyT (BIO2001-1235- C03-01 and GEN2001-4856-C13-11)., M. C. acknowledges financial support from I3P-CSIC and MERG-CT-2004-510638. J. T. and M. A. acknowledge financial support from MCyT (BIO2001-1235- C03-01 and GEN2001-4856-C13-11).

6 páginas, 6 figuras., Biomolecular interactions over the surface of a microcantilever can produce its bending motion via changes of the surface stress, which is referred to nanomechanical response. Here, we have studied the interaction forces responsible for the bending motion during the formation of a self-assembled monolayer of thiolated 27-mer single-stranded DNA on the gold-coated side of a microcantilever and during the subsequent hybridization with the complementary nucleic acid. The immobilization of the single-stranded DNA probe gives a mean surface stress of 25 mN/m and a mean bending of 23 nm for microcantilevers with a length and thickness of about 200 μm and 0.8 μm, respectively. The hybridization with the complementary sequence could not be inferred from the nanomechanical response. The nanomechanical response was compared with data from well-established techniques such as surface plasmon resonance and radiolabeling, to determine the surface coverage and study the intermolecular forces between neighboring DNA molecules anchored to the microcantilever surface. From both techniques, an immobilization surface density of 3 × 1012 molecules/cm2 and a hybridization efficiency of 40% were determined. More importantly, label-free hybridization was clearly detected in the same conditions with a conventional sensor based on surface plasmon resonance. The results imply that the nanomechanical signal during the immobilization process arises mainly from the covalent attachment to the gold surface, and the interchain interactions between neighboring DNA molecules are weak, producing an undetectable surface stress. We conclude that detection of nucleic acid hybridization with nanomechanical sensors requires reference cantilevers to remove nonspecific signals, more sensitive microcantilever geometries, and immobilization chemistries specially addressed to enhance the surface stress variations., This work was supported by the MyCT (BIO2001-1235-C03-01).

10 páginas, 6 figuras.-- Trabajo presentado en la conferencia "Nanotechnology"; Maspalomas, Gran Canaria (España); 19-Mayo-2003; Editores: Robert Vajtai, Xavier Aymerich, Laszlo B. Kish, Angel Rubio., Nanomechanical biosensors have emerged as a promising platform for specific biological. Among the advantages are direct detection without need of labelling with fluorescent or radioactive molecules, very high sensitivity, reduced sensor area, and suitability for integration using silicon technology. Here we have studied the immobilization of oligonucleotide monolayers by monitoring the microcantilever bending. Oligonucleotides were derivatized with thiol molecules for self-assembly on the gold-coated side of a microcantilever. The geometry of the binding and the surface density were studied by mixing derivatized oligonucleotides with spacer self-assembled monolayers and by controlling the oligonucleotide functional group form. These results are compared with fluoresencent and chemiluminescence techniques. Furthermore, we present the first results of direct pesticide detection with microcantilever-based biosensors. Herbicide DDT was detected by performing competitive assays, in which the cantilever was coated with a synthetic DDT hapten, and it was exposured to different rations between the monoclonal antibody and the DDT. A new technique is presented for the detection of the nanomechanical response for biosensing applications, in which the resonant frequency is measured with about two orders of magnitude higher sensitivity. The low quality factor of the microcantilever in liquid is increased up by using an active feedback control, in which the cantilever oscillation is amplified and delayed and it is used as a driving force. The technique has been applied for the detection of ethanol, proteins, and pathogens., This work was supported by the Spanish Ministry of Science and Technology (MCyT), project BIO2001-1235-C03-01. Mar Álvarez acknowledge the grant from the MCyT.

We present a straightforward and rapid surface acoustic wave SAW atomizationbased technique for encapsulating proteins into 10 m order particles composed of a biodegradable polymeric excipient, using bovine serum albumin BSA as an exemplar. Scans obtained from confocal microscopy provide qualitative proof of encapsulation and show the fluorescent conjugated protein to be distributed in a relatively uniform manner within the polymer shell. An ELISA assay of the collected particles demonstrates that the BSA survives the atomization, particle formation, and collection process with a yield of approximately 55%. The SAW atomization universally gave particles with a textured morphology, and increasing the frequency and polymer concentration generally gave smaller particles to 3 m average with reduced porosity. © 2009 American Institute of Physics. DOI: 10.1063/1.3055282

7 pages, 5 figures, 1 table., Thermomechanical noise determines the lowest detection limits of microcantilever-based devices for measuring forces and surface stress variations. In this work, arrays of 334-nm-thick single-crystalline silicon microcantilevers with dissimilar lengths and widths from 50 to 500 µm and 20 to 200 µm, respectively, have been fabricated to calculate the minimal detectable force and surface stress on the basis of the measurement of the spring constant, resonance frequency, and quality factor. The calculated minimal detectable force and surface stress are of the orders of 10–15 N Hz–1/2 and 10–7 N m–1 Hz–1/2, respectively, and both follow a nonintuitive dependence on the dimensions. The minimal detectable force decreases as the cantilevers are shorter and narrower, whereas the minimal detectable surface stress decreases by making the cantilevers shorter and wider. Theoretical expressions of the minimal detectable force and surface stress are provided as a function of the material properties, cantilever dimensions, and quality factor, which allow us to interpret the results. Both force and surface stress noises follow the same dependence on the quality factor and material properties, however, exhibit striking differences in the dimension dependences. The force and surface stress noises enhance with the quality factor. If the quality factor is kept constant, the force noise enhances as the cantilever is longer and wider, whereas the surface stress noise enhances by making the cantilever shorter and wider. The observed increase of the force noise with the length is attributed to the strong decrease of the quality factor. The results imply that the design of cantilevers for surface stress measurements in general should be different than for atomic force microscopy probes., The authors would like to acknowledge the European Union (IST-2001-37239) and the Spanish Ministry of Science (GEN2001-4856-C13-11 and TIC2002-10473-E) for the financial support.