Cantilever Array Research Articles

All-optical background subtraction readout method for bimaterial cantilever array sensing.

Optical readout method plays a critical role in bimaterial cantilever array sensing system. The common optical readout methods are based on spectral plane filtering. In the paper an all-optical background subtraction readout approach inspired by total reflection and optical lever principle is presented for the bimaterial cantilever array sensing. Comparing with the spectral plane filtering methods the proposed approach eliminates digital subtraction operation by using optical total reflection instead of digital subtraction and avoids spectral filtering operation. An all-optical background subtraction directly-view infrared sensing system was developed to evaluate the approach. The infrared target can be directly acquired by the visible light CCD. The experimental results and analysis show its unique advantages.

Nanomechanical humidity detection through porous alumina cantilevers.

We present here the behavior of the resonance frequency of porous anodic alumina cantilever arrays during water vapor adsorption and emphasize their possible use in the micromechanical sensing of humidity levels at least in the range of 10–22%. The sensitivity of porous anodic aluminium oxide cantilevers (Δf/Δm) and the humidity sensitivity equal about 56 Hz/pg and about 100 Hz/%, respectively. The approach presented here for the design of anodic alumina cantilever arrays by the combination of anodic oxidation and photolithography enables easy control over porosity, surface area, geometric and mechanical characteristics of the cantilever arrays for micromechanical sensing.

Periodic Array of Subwavelength MEMS Cantilevers for Dynamic Manipulation of Terahertz Waves

We experimentally demonstrate the active manipulation of terahertz (THz) waves using a periodic array of electrostatically actuated subwavelength microelectromechanical system cantilevers, which effectively behave like a metamaterial. The design methodology for achieving desired ON- and OFF-state resonance frequencies through electromechanical optimization is presented. The microcantilever metamaterial has a switching range of 0.29 THz and a modulation depth of 60% at 0.59 THz. Utilizing metal layer thickness to optimize the devices, an improvement of 40% is achieved in switching range. The microcantilever metamaterials are highly miniaturized, extremely scalable, and electrically controlled with attractive electro-optic performance. Multiple cantilevers can be placed in a desired fashion to form complex unit cell geometry to realize advanced THz manipulation, such as polarization switching, bandwidth tunable filters, multicolor imagers, and so on.

Design and fabrication of electrostatic micro-cantilever array as audible frequency generator

Abstract In assistive technologies involving voice communication, an audio signal with specific shape is needed. In this regard, the design and fabrication of an electrostatic cantilever array is proposed. An array of four metallic micro-cantilevers with dimensions 650 μm × 200 μm × 0.3 μm is fabricated on the silicon substrate. The working principle is based on the electrostatic effect generated due to a conductive path applied between the electrodes. The results are taken from zinc oxide (ZnO) piezoelectric thin film that allows making contact with the vibrating cantilevers on a specified applied input impulse signals. The results demonstrated the switching action of the cantilevers that depends on the polarity of the input pulses. The results obtained are compared with the FEM based (COMSOL Multiphysics) model that is designed and analyzed prior to the experiment. Further, the experimental results showed a good agreement with the predicted values calculated by the simulated model for the input impulse signal applied synchronously to all the micro-cantilevers. However, for asynchronous actuation mode, the result of the as-fabricated device showed a variation than the simulated results. The vibrations are generated periodically from all the cantilevers and the output shows the resultant signals that are very much in the audible frequency range.

An optimized measurement chamber for cantilever array measurements in liquid incorporating an automated sample handling system

Micro- and nanomechanical analytical devices for diagnostics require small sample volumes, and stable and efficient clamping of the sensors for optimized bioassays. A fully automated device for the readout of the dynamic and static response of cantilevers in a physiological liquid environment including a sample handling system is presented. The device provides sequential readout of the static and dynamic mode providing the best signal to noise ratio for each individual cantilever. In the dynamic mode, it is possible to measure up to the 16th flexural resonance mode of vibration of a 500 μm long and 1 μm thick cantilever. The automated sample handling system enables the local injection of sub microliter volumes of sample with excellent reproducibility. Data demonstrating the response of the cantilevers to external stimuli highlight the sensitivity of the device and the importance of the use of reference cantilevers to decouple biologically relevant metrics from environmental effects. A specific biomolecular interaction of sensitised nanospheres on cantilever sensors with a mass resolution of ~50 picogram in liquid is shown. PACS numbers: 07.10 Mechanical instruments, 87.85 Biosensors, 47.85. Fluidic

박막 캔틸레버 어레이 센서를 이용한 질병 진단기 설계 및 구현

The disease diagnosis system has been developed using the thin nitride(Si3N4) cantilever arrays which can measure the difference of capacitances between sensor and reference. The system consists of 32-bits RISC(Reduced Instruction Set Computer), RAM/Flash, bus, communication IP's, ADC(Analog Digital Converter) board, and LCD display. The marker selection method, which give us the good accuracy from reasonal numbers of markers, is suggested. The developed system has the resolution under 1fF and can detect 10nM concentration of Thrombin.

Image quality improvement by the structured light illumination method in an optical readout cantilever array infrared imaging system.

The structured light illumination method is applied in an optical readout uncooled infrared imaging system to improve the IR image quality. The unavoidable nonuniform distribution of the initial bending angles of the bimaterial cantilever pixels in the focal plane array (FPA) can be well compensated by this method. An ordinary projector is used to generate structured lights of different intensity distribution. The projected light is divided into patches of rectangular regions, and the brightness of each region can be set automatically according to the deflection angles of the FPA and the light intensity focused on the imaging plane. By this method, the FPA image on the CCD plane can be much more uniform and the image quality of the IR target improved significantly. A comparative experiment is designed to verify the effectiveness. The theoretical analysis and experimental results show that the proposed structured light illumination method outperforms the conventional one, especially when it is difficult to perfect the FPA fabrication.

Performance enhancement of uncooled infrared focal plane array by integrating metamaterial absorber

This letter presents an infrared (IR) focal plane array (FPA) with metamaterial absorber (MMA) integrated to enhance its performance. A glass substrate, on which arrays of bimaterial cantilevers are fabricated as the thermal-sensitive pixels by a polyimide surface sacrificial process, is employed to allow the optical readout from the back side of the substrate. Whereas the IR wave radiates onto the FPA from the front side, which consequently avoids the energy loss caused by the silicon substrate compared with the previous works. This structure also facilitates the integration of MMA by introducing a layer of periodic square resonators atop the SiNx structural layer to form a metal/dielectric/metal stack with the gold mirror functioning as the ground plane. A comparative experiment was carried out on the FPAs that use MMA and ordinary SiNx as the absorbers, respectively. The performance improvement was verified by the evaluation of the absorbers as well as the imaging results of both FPAs.

Nanosensors for cancer detection.

Cancer is a major burden in today's society and one of the leading causes of death in industrialised countries. Various avenues for the detection of cancer exist, most of which rely on standard methods, such as histology, ELISA, and PCR. Here we put the focus on nanomechanical biosensors derived from atomic force microscopy cantilevers. The versatility of this novel technology has been demonstrated in different applications and in some ways surpasses current technologies, such as microarray, quartz crystal microbalance and surface plasmon resonance. The technology enables label free biomarker detection without the necessity of target amplification in a total cellular background, such as BRAF mutation analysis in malignant melanoma. A unique application of the cantilever array format is the analysis of conformational dynamics of membrane proteins associated to surface stress changes. Another development is characterisation of exhaled breath which allows assessment of a patient's condition in a non-invasive manner.

Viscosity measurement based on the tapping-induced free vibration of sessile droplets using MEMS-based piezoresistive cantilevers.

We report a simple technique to measure the free vibration of microlitre-sized droplets using an array of thirteen MEMS-based piezoresistive cantilevers and demonstrate its application for the measurement of viscosity. Because the damping of the free vibration of a liquid droplet is known to be affected by the viscosity of the liquid, measuring the vibration of a droplet allows the viscosity to be estimated from a dilute sample volume. However, conventional methods to measure the droplet vibration require sophisticated apparatuses, which hinder the development of a portable viscometer. Here, we show that MEMS-based piezoresistive cantilevers can be an excellent tool to measure the vibration of a sessile droplet due to the high sensitivity and simplicity of the readout scheme. Using the cantilever array, we analyse the normal force distribution on the contact area of a sessile droplet in the static state and during the vibration. Next, we show that the viscosity (from ~1-30 mPa s) can be estimated within an error of less than 10% from the attenuation rate of the cantilever output during the tapping-induced vibration of small droplets (~2.4 μL). In addition to the advantage of the small sample volume, the proposed viscometer has simple operation and readout schemes, which are desirable for many applications, including point-of-care testing and drug development.

Dynamics of impurity attraction and repulsion of an intrinsic localized mode in a driven 1-D cantilever array.

Both low frequency and high frequency impurity modes have been produced in a SiN micromechanical cantilever array by illumination with either an infrared or visible laser. When such laser-induced impurities are placed near a driven intrinsic localized mode (ILM), it is either repelled or attracted. By measuring the linear response spectrum for these two cases, it was found that vibrational hopping of the ILM takes place when the natural frequency of the ILM and an intrinsic even symmetry linear local mode are symmetrically located about the driven ILM frequency so that parametric excitation of these two linear modes is enhanced, amplifying the lateral motion of the ILM. Numerical simulations are consistent with these signature findings. It is also demonstrated that the correct sign of the observed interaction can be found with a harmonic lattice-impurity model but the magnitude of the effect is enhanced in a nonlinear lattice.

Micro electro-mechanical system piezoelectric cantilever array for a broadband vibration energy harvester.

Limited energy sources of ubiquitous sensor networks (USNs) such as fuel cells and batteries have grave drawbacks such as the need for replacements and re-charging owing to their short durability and environmental pollution. Energy harvesting which is converting environmental mechanical vibration into electrical energy has been researched with some piezoelectric materials and various cantilever designs to increase the efficiency of energy-harvesting devices. In this study, we focused on an energy-harvesting cantilever with a broadband vibration frequency. We fabricated a lead zirconate titanate (PZT) cantilever array with various Si proof masses on small beams (5.5 mm x 0.5 mm x 0.5 mm). We obtained broadband resonant frequencies ranging between 127 Hz and 136 Hz using a micro electro-mechanical system (MEMS) process. In order to obtain broadband resonant characteristics, the cantilever array was comprised of six cantilevers with different resonant frequencies. We obtained an output power of about 2.461 μW at an acceleration of 0.23 g and a resistance of 4 kΩ. The measured bandwidth of the resonant frequency was approximately 9 Hz (127-136 Hz), which is about six times wider than the bandwidth of a single cantilever.

Cantilevers for biological monitoring: opportunities for classical and quantum physics

For 20 years, cantilevers have been used in different research fields as fast, accurate and label-free sensors in liquid, gas, air and vacuum. Due to their small size, they can be integrated into microfluidic systems and offer possibilities for various applications in lab-on-chip technology. Furthermore, multiple cantilevers, the so-called cantilever arrays, provide a direct internal reference during the measuring process and enable the parallel monitoring of several different analytes. This review provides a general introduction into the history and theory of cantilever sensors, with an emphasis on biological monitoring applications as opportunities for classical and quantum physics. Furthermore, it includes recent developments in novel transduction principles and applications, and discusses future prospects.

A hybrid micro vibration energy harvester with power management circuit

In this paper, a hybrid micro vibration energy harvester based on piezoelectric and electromagnetic transduction mechanisms is developed and tested, which improves total output power and voltage in low frequency and small amplitude vibration environment. It contains a MEMS piezoelectric (PZT) cantilever array with an integrated Si proof mass, an NdFeB magnet attached to the free end of the cantilever beam, and one multi-layer micro coil fabricated using standard PCB technology placed on the fixed bottom. A mathematical model is established to calculate the output power from the hybrid energy harvester. The optimum size of the device’s structure is obtained based on the finite element analysis. Experimental test results show that the maximum output power of 40.62μW can be drawn from the hybrid energy harvester with the optimal load resistance under the vibration of 0.2g acceleration at the resonant frequency of 55.9Hz. The more power output can be generated than a stand-alone piezoelectric or electromagnetic device, and the output voltage is increased by using the MEMS PZT cantilever array architecture. In order to regulate the output voltage of energy transducer, a low power consumption power management circuit integrated with AC–DC rectifier and DC–DC buck converter is designed and applied in wireless sensor nodes. The test results prove that the hybrid energy harvester can provide a stable output power supply voltage of 3.6V for wireless sensor node.

Utilization of microscale silicon cantilevers to assess cellular contractile function in vitro.

The development of more predictive and biologically relevant in vitro assays is predicated on the advancement of versatile cell culture systems which facilitate the functional assessment of the seeded cells. To that end, microscale cantilever technology offers a platform with which to measure the contractile functionality of a range of cell types, including skeletal, cardiac, and smooth muscle cells, through assessment of contraction induced substrate bending. Application of multiplexed cantilever arrays provides the means to develop moderate to high-throughput protocols for assessing drug efficacy and toxicity, disease phenotype and progression, as well as neuromuscular and other cell-cell interactions. This manuscript provides the details for fabricating reliable cantilever arrays for this purpose, and the methods required to successfully culture cells on these surfaces. Further description is provided on the steps necessary to perform functional analysis of contractile cell types maintained on such arrays using a novel laser and photo-detector system. The representative data provided highlights the precision and reproducible nature of the analysis of contractile function possible using this system, as well as the wide range of studies to which such technology can be applied. Successful widespread adoption of this system could provide investigators with the means to perform rapid, low cost functional studies in vitro, leading to more accurate predictions of tissue performance, disease development and response to novel therapeutic treatment.

Analysis of rectangular and triangular end array type piezoelectric vibration energy harvester

A new array type cantilever structure with improved bandwidth and enhanced power output is proposed in this paper. Instead of having a normal rectangular end, the proposed cantilever will have triangular end with proof mass which will increase the power output and further the power is improved by having an array structure. In the array of cantilever, each structure will be having different proof mass so that the frequency with which they vibrate will differ. By using this new array structure of cantilever, bandwidth of 39 Hz and power of 7 µW is generated for rectangular end and bandwidth of 48 Hz and power of 8 µW is generated for triangular end.

Collective dynamics and pattern switching in an array of parametrically excited micro cantilevers interacting through fringing electrostatic fields

We report on an experimental observation of synchronization and abrupt transitions between standing wave patterns in arrays of micromechanical oscillators. The architecture of flexible cantilever arrays parametrically excited by and interacting through time-dependent fringing electrostatic fields allows tuning of an interaction potential and supports traveling waves. The arrays consisting of 500 μm long and 5 μm thick single crystal Si cantilevers were fabricated from silicon on insulator substrates. The out-of-plane resonant responses were visualized by time-averaged temporally aliased video imaging and measured by laser Doppler vibrometry. Our experimental and reduced order model results collectively demonstrate that under a slowly varying drive frequency the standing wave patterns remain unchanged in certain frequencies intervals, followed by an abrupt change in the pattern.

Lab-on-Chip Microfluidics System for Single Cell Mass Measurement: A Comprehensive Review

Single cell mass (SCM) is one of the intrinsic properties of cell and is a vital part of single cell analysis (SCA). To date, a myriad numbers of works has been successfully reported for single cell mass measurement but the reported information are scattered, consequently a comprehensive review becomes mandatory to bring them together. Lab-on-chip microfluidics system integrated with micro-resonator provided an excellent platform to measure single cell mass directly (in presence of cells). On-chip microfluidics system like suspended micro channel resonator (SMR) was reported for non-adherent single yeast cell mass while ‘living cantilever arrays’ (LCA) was proposed to measure adherent HeLa cell mass. On the other hand, cantilever based resonant mass measurement system has non-uniform mass sensitivity; this issue has been overcome by pedestal mass measurement system (PMMS). PMMS has a unique geometrical structure that provided uniform mass sensitivity to the sensing surface. Moreover, we presented a comprehensive discussion of each of the available methods of SCM elaborating the sensing mechanism, geometry of the sensor and governing equations. It is hoped that, information presented in this comprehensive review paper will be a valuable source for the single cell mass analysers and biological researchers.

Design and fabrication of a mems test socket with an attached tip for a ball-grid-array integrated circuit package

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 XeF2 isotropic silicon etching. The electroplating process was used to create metal tips and thick metal cantilevers, which increased the contact reliability and conductivity. XeF2 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.

Reversible detection of vancomycin using peptide-functionalized cantilever array sensor

A reversible detection method for vancomycin was developed utilizing the cantilever array sensor functionalized by a designed peptide consisting of a cysteine (Cys-), a space linker (-Gly-Gly-Gly-Gly-) and a molecular recognition ligand (-l-Lys-d-Ala-d-Ala). It was found that the peptide space linker was necessary and important for the response of the cantilever array sensor. The sensing cantilevers in the array were functionalized with the peptide while the reference cantilevers were modified by 6-mercapto-1-hexanol (MCH) to eliminate the influence of environmental disturbances. The binding between vancomycin and the peptide induced a change of surface stresses in the sensing cantilevers resulting in a differential deflection between the sensing and reference cantilevers. The reciprocal of the differential deflection is linear with the reciprocal of vancomycin concentration within the range of 2μM to 100μM (R=0.993) at a detection limit of 0.2μM (S/N=3). The reversible detection can be realized just by regenerating the sensing cantilevers with running buffer solution. Other antibiotics such as doxycycline, streptomycin, and kanamycin have negligible effect on the response of the sensor. The sensor can also be utilized for reversible detection of vancomycin in serum background, which clearly indicates the potential of the sensor for vancomycin detection in real biological samples.