Parallel Cantilever Research Articles

An integrated hinged dual-probe for co-target fast switching imaging.

The diversity of functional applications of atomic force microscopes is the key to the development of nanotechnology. However, the single probe configuration of the traditional atomic force microscope restricts the realization of different application requirements for the same target area of a single sample, and the replacement of the working probe will lead to the loss of the target area. Here, the design, simulation, fabrication, and application of a unique atomic force microscope dual-probe are presented, which consists of a pair of parallel cantilevers with a narrow gap and a U-shaped hinged probe base. The Integrated Hinged Dual-Probe (IHDP) is developed specifically for fast switching of probes working in limited space and independent and precise manipulation of each probe. The deflection signal sensing of two cantilevers is achieved simultaneously by a single laser beam, and the decoupled independent cantilever deflection signals do not interfere with each other. The switching of the working probe is achieved by a piezoelectric ceramic with a 2 µm stroke and U-shaped hinge structure, which is fast and does not require tedious and repetitive spatial position calibration. By measuring standard grid samples, IHDP exhibits excellent measurement and characterization capabilities. Finally, a working probe switching imaging experiment was conducted on solidified rat cardiomyocytes, and the experimental process and imaging results demonstrated the superiority of IHDP in switching probe scanning imaging of the same target area of a single sample. The two probes of IHDP can undergo arbitrary functionalization modifications, which helps achieve multidimensional information acquisition for a single target.

Low-temperature processing of screen-printed piezoelectric KNbO3 with integration onto biodegradable paper substrates

The development of fully solution-processed, biodegradable piezoelectrics is a critical step in the development of green electronics towards the worldwide reduction of harmful electronic waste. However, recent printing processes for piezoelectrics are hindered by the high sintering temperatures required for conventional perovskite fabrication techniques. Thus, a process was developed to manufacture lead-free printed piezoelectric devices at low temperatures to enable integration with eco-friendly substrates and electrodes. A printable ink was developed for screen printing potassium niobate (KNbO3) piezoelectric layers in microns of thickness at a maximum processing temperature of 120 °C with high reproducibility. Characteristic parallel plate capacitor and cantilever devices were designed and manufactured to assess the quality of this ink and evaluate its physical, dielectric, and piezoelectric characteristics; including a comparison of behaviour between conventional silicon and biodegradable paper substrates. The printed layers were 10.7–11.2 μm thick, with acceptable surface roughness values in the range of 0.4–1.1 μm. The relative permittivity of the piezoelectric layer was 29.3. The poling parameters were optimised for the piezoelectric response, with an average longitudinal piezoelectric coefficient for samples printed on paper substrates measured as d33, eff, paper = 13.57 ± 2.84 pC/N; the largest measured value was 18.37 pC/N on paper substrates. This approach to printable biodegradable piezoelectrics opens the way forward for fully solution-processed green piezoelectric devices.

A Hybrid Piezoelectric and Electromagnetic Broadband Harvester with Double Cantilever Beams

Vibration-energy harvesting is an effective strategy for replacing batteries and provides a long-term power supply to microelectronic devices. Harvesting vibration energy from human motions has attracted research attention in recent years. Here, a novel low-frequency hybrid piezoelectric and electromagnetic broadband harvester is proposed. Two parallel piezoelectric cantilever beams support the harvester and capture environmental vibration energy based on the piezoelectric effect. A permanent magnet is connected by springs to the two beams, and a fixed coil surrounds the moving permanent magnet, enabling energy conversion via the electromagnetic effect and the proof mass. The parameters influencing the output power of the harvester are optimized numerically to boost the harvester's performance. The output power of the proposed hybrid harvester is compared with that of a piezoelectric harvester and an electromagnetic harvester. The simulation results show that the output power is significantly higher for the hybrid harvester than for the piezoelectric and electromagnetic harvesters, and the bandwidth is broader owing to the double cantilevers. An experiment is conducted using a prototype of the hybrid harvester to evaluate its output power. The results show multiple resonant peaks, an extended bandwidth, and a maximum power of 6.28 mW. In contrast, the maximum harvested power of the piezoelectric harvester is only 5.15 mW at 9.6 Hz.

Development and Optimization of a Two-Degree-of-Freedom Piezoelectric Harvester Based on Parallel Cantilever Structure With Magnetic Coupling

Development and Optimization of a Two-Degree-of-Freedom Piezoelectric Harvester Based on Parallel Cantilever Structure With Magnetic Coupling

Nonlinear system identification based on restoring force transmissibility of vibrating structures

In vibrating elastic structures, the motion at locations with no external load is induced by internal forces and due to transmissibility. This capability is utilized in this paper for parameter estimation of nonlinear structures in the absence of input measurements. It is demonstrated that the nonlinearities are detectable at degrees of freedom away from the excitation with no need for input measurements and mass matrix information. To estimate the linear and nonlinear parameters within the physical equations of motion, the proposed approach is utilized in conjunction with a new data-driven subspace identification algorithm. The idea is to project the output measurements onto the basis function that is used for predicting the restoring force, and then separate the nonlinear dynamics from the underlying linear system. The proposed approach is implemented and examined for different structural nonlinearity types and compared to other methods. Moreover, the vibro-impact parameters of three parallel cantilever beams with non-equidistant gaps are experimentally investigated. The results address the feasibility range of the transmissibility-based subspace algorithm for the identification of a broad class of structural nonlinearities when the excitation loads are not measurable.

A novel remotely-controlled gripper based on magnetostrictive material

A novel gripper based on magnetostriction phenomena is proposed in this study. The gripper is formed of two parallel cantilever beams each composed of a steel layer laminated by Metglas (2605SC) as the magnetostrictive material. The main advantage of the proposed gripper over the pioneer ones is its remote controllability. Once the gripper is subjected to a magnetic field with appropriate amplitude, the Metglas 2605SC undergoes mechanical strain and as a result, the cantilever beams bend toward each other and accordingly contact takes place between the cantilevers and the object in-between. The motion equation is derived and the reduced order model is obtained by means of Galerkin technique. The effects of the intensity of the magnetic field, as well as the damping effect on the temporal response of the gripper, are studied and reported as well.

Multi‐contact radiofrequency microelectromechanical systems switch with power divider/combiner structure for high power applications

Design, fabrication, and measurement of a metal-contact radiofrequency (RF) microelectromechanical systems switch with a power divider/combiner structure for high power applications are presented in this work. The multi-contact switch with parallel cantilever beams is implemented in a Y-junction power divider/combiner, which suppresses the uneven current distribution through each contact and results in higher power handling capability at high frequency. The measurement results indicate the excellent RF performance of the switch fabricated on the Borofloat glass substrate with insertion loss and isolation of 0.22 dB and 29 dB@10 GHz, respectively. A lumped-element model is developed and it fits well with the measured S-parameters with the contact resistance of 0.6 Ω and up-state capacitance of 1 fF for each contact. The switch can handle power up to 2 W@10 GHz under prolonged hold-down conditions for 2 h. The reliability measurement shows that the packaged switch can operate for over 1 million cycles at 200 mA under cold-switching conditions.

A Paper-Based Piezoelectric Accelerometer.

This paper presents the design and testing of a one-axis piezoelectric accelerometer made from cellulose paper and piezoelectric zinc oxide nanowires (ZnO NWs) hydrothermally grown on paper. The accelerometer adopts a cantilever-based configuration with two parallel cantilever beams attached with a paper proof mass. A piece of U-shaped, ZnO-NW-coated paper is attached on top of the parallel beams, serving as the strain sensing element for acceleration measurement. The electric charges produced from the ZnO-NW-coated paper are converted into a voltage output using a custom-made charge amplifier circuit. The device fabrication only involves cutting of paper and hydrothermal growth of ZnO NWs, and does not require the access to expensive and sophisticated equipment. The performance of the devices with different weight growth percentages of the ZnO NWs was characterized.

Large area fast-AFM scanning with active “Quattro” cantilever arrays

In this work, the fabrication and operation of an active parallel cantilever device integrating four self-sensing and self-actuating probes in an array is presented. The so called “Quattro” cantilever system is controlled by a multichannel field programmable gate array (FPGA) controller. The integrated cantilever devices are fabricated on the basis of a silicon-on-insulator wafer using surface micromachining and gas chopping plasma-etching processes [I. W. Rangelow, J. Vac. Sci. Technol., A 21, 1550 (2003)]. The unique design of the active cantilever probes provides both patterning and readout capabilities [Kaestner et al., J. Micro-Nanolithogr. MEMS 14, 031202 (2015)]. The thermomechanical actuation allows the individually operation of each cantilever in static and dynamic modes. This enables a simultaneous atomic force microscopy operation of all cantilevers in an array, while the piezoresistive read-out of the cantilever bending routinely ensures atomic resolution at a high imaging speed. The scanning probe lithography capabilities of the active cantilevers are based on the utilization of a Fowler–Nordheim field emission process of low-energy electrons (20–50 eV) for direct writing maskless lithography. The cantilever in the Quattro active cantilever array have a pitch of 125 μm (tip-to-tip distance), which allows an image size of 0.5 × 0.2 mm to be acquired within a single scan with 0.2 nm resolution in the vertical direction. Using parallel imaging, an effective scanning speed of 5.6 mm/s is achieved. The multichannel, scalable controller architecture allows four FPGA channels to scan and collect data simultaneously. A data buffer of 128 Mbits for a single frame of 4096 × 1024 pixels is applied. The designed data transfer system allows a packet size of 128 pixels to be transmitted within less than 10 μs, respectively. Thus, the entire image frame is transferred in less than 280 ms, which exceeds the required throughput in the practical cases like critical dimension-metrology and inspection. In this article, the authors are presenting the concept of the system, which combines imaging, metrology, and lithography capabilities with a low-cost of ownership. In this context, the authors are investigating the throughput capability, reproducibility, resolution, and positioning accuracy of the Quattro active cantilever system.

Simulation and experimental demonstration of improved efficiency in coupled piezoelectric cantilevers by extended strain distribution

A piezoelectric energy harvester design is proposed, which will achieve a wider bandwidth without compromising energy conversion efficiency for future use in e g gas turbines. By coupling two cantilevers where the tip of the bottom one is attached to the base of the upper one, the harvester will have a wider bandwidth and a higher power output compared to two optimally tuned single cantilevers, which to a large part is the effect of an extended strain distribution in the bottom cantilever in the coupled configuration. The design is compact, using only half the area compared to two parallel single cantilevers at the price of only a small increase in height. The coupled harvester displays approximately five times higher power output than two tuned single cantilevers.

Modelling and experimental verification of more efficient power harvesting by coupled piezoelectric cantilevers

A new piezoelectric energy harvester design is proposed in order to achieve a wider bandwidth without compromising energy conversion efficiency. By coupling two cantilevers where the tip of the bottom one is attached to the base of the upper one, the simulated harvester will have a wider bandwidth and higher power output compared with two simulated single tuned single cantilevers. This is a compact design, using only half the area compared to two parallel single cantilevers at the price of a small increase in height. The measured coupled harvester has approximately 1.7 times higher energy output than the combination of two measured tuned single cantilevers achieved by a coupling with less mechanical damping. With an improved coupling the power output is increased to 2.3 times higher than two single tuned cantilevers.

Modeling the instability of CNT tweezers using a continuum model

Carbon nanotube (CNT) tweezers are composed of two parallel cantilever CNTs with a distance in between. In this paper, the static response and instability of CNT-made nano-tweezers is theoretically investigated considering the effects of Coulomb electrostatic force and van der Waals molecular attraction. For this purpose, a nano-scale continuum model is employed to obtain the nonlinear constitutive equation of the nano-tweezers. The Euler–Bernoulli beam theory is applied to model the elastic response of the CNT. The van der Waals attraction is computed from the simplified Lennard-Jones potential. In order to solve the nonlinear constitutive equation of the system, three approaches, e.g. the hemotopy perturbation method (HPM), the Adomian decomposition (AD) and the finite difference method (FDM) are employed. The obtained results are in good agreement with the experimental measurements. As a case study, freestanding CNT tweezers has been investigated and the detachment length and minimum initial gap of the tweezers are determined. Moreover, the effective operation range of the van der Waals attraction that affects the instability behavior of the CNT tweezers is discussed.

A photoresponse-compensated parallel piezoresistive cantilever for cellular force measurements

This paper describes a parallel piezoresistive cantilever that is composed of a force-sensing cantilever in addition to a reference cantilever for photoresponse compensation. Piezoresistive cantilevers have been applied in many cellular mechanical measurement studies because of their high sensitivity, high time resolution and ease of handling. However, the electrical resistance changes in response to the excitation light of the fluorescence microscope, which affects the cell measurements. We measured the I–V characteristics of a piezoresistive layer. These photoresponses occurred due to the internal photoelectric effect. We canceled the photoresponses using the reference cantilever. This paper demonstrates compensation of the cantilever photoresponse under irradiation at different angles, wavelengths and light intensities. As a result, the photoresponse could be decreased by 87%.

Low-Power Design of a Self-powered Piezoelectric Energy Harvesting System With Maximum Power Point Tracking

A low-power energy harvesting system targeting to harvest several milliwatts from vibration is presented in this paper. Several low-power design schemes to reduce power dissipation of the proposed system are described, and sources of power loss are analyzed to improve the power efficiency. A discontinuous conduction mode (DCM) flyback converter with the constant on-time modulation is adopted for our system. The DCM operation of a flyback converter is chosen as for maximum power point tracking (MPPT) to be implemented with a single current sensor. The constant on-time modulation lowers the clock frequency of the controller by more than an order of magnitude for our system, which reduces the dynamic power dissipation of the controller. MPPT, executed by a microcontroller unit (MCU), is achieved through dynamic resistive matching, and the MPPT is executed at intermittent time intervals due to a relatively slow change of the operating condition. When MPPT is not active, the MCU operates at a lower clock frequency to save power. Experimental results indicate that the proposed system harvests up to 8.4 mW power under 0.5-g base acceleration with four parallel piezoelectric cantilevers and achieves 72% power efficiency around the resonant frequency of 47 Hz.

Magnetically-Coupled Cantilevers with Antiphase Bistable Behavior for Kinetic Energy Harvesting

Abstract This work deals with bistable devices for vibration energy harvesting. We have addressed this subject through MEMS cantilevers and the use of two facing magnets, with opposed magnetization, in order to obtain the desired double-well potential energy function. However the fabrication on MEMS devices of micromagnets placed very close one each other and having non-parallel magnetization is seriously challenging: parallel magnetization would be greatly preferable. Based on this latter consideration, new device architecture is presented here: two parallel cantilevers, with a magnet on each tip, are used. The two magnets are equally oriented and therefore provide repulsive forces that in turn induce antisymmetric bistable behaviors in the two cantilevers. The system has been analytically modeled and an experimental prototype has been realized and tested obtaining very promising results.

Design of Double T-Shape Accelerometer Based on MEMS

A novel structure is proposed to design accelerometer, that is, two parallel cantilever beams are selected instead of single-beam, which would effectively improve accelerometer’s sensitivity. The novel structure can be integrated fabricated, which is suit for lot manufacturing. The characteristic parameters of the microstructure are analyzed by ANSYS. It can be concluded that the sensitivity is, anti-overload capacity is 1e5g, measuring range is±20g.The microstructure is manufactured by means of the silicon-on-insulator craft and the thickness of the beam is 20 um, the length is 3500 um. The test results show that the resonance frequency is 1840Hz, which is consistent with the results of the calculation and simulation.

A Piezoelectrically Actuated Scaning Micromirror Integrated with Angle Sensors

A novel piezoelectrically actuated scanning micromirror integrated with angle sensors is presented. The mirror with large size of 3×3mm2 locates in the center of the device, and piezoelectric actuators are symmetrically placed on both sides of the mirror. They are connected through torsion bars in which piezoelectric angle sensors are integrated. In order to obtain large deflection angle at a low operation voltage, the new actuator consisting of several parallel piezoelectric cantilevers is adopted. The machematical models of the mirror and piezoelectric actuator are given, and the piezoelectric angle sensors are designed to obtain high sensitivities. The simulation results indicate that the maximum mechanical deflection angle of the micromirror is 12.4° at an operation voltage of 25V, and the maximum output voltage of the angle sensor is 164.3mV. The resonant frequency associated with the torsional mode is 960Hz. The sensitivity of the angle sensor is 13.3mV/° without amplifying. The Scanning miromirror is suitable for optical scanning systems such as the microscope, the micro-spectrometer, the medical imaging, the barcode reader and so on.

Micro Friction Experimental Study Based on Parallel Cantilever

In this paper, the law of micro-friction in meso-scale is studied, one optical testing method of micro friction based on the structure of parallel cantilever is given and the testing system is designed, the composition of test system, testing method, the design of force sensor, the testing method and the calibration of force sensor are introduced. The force sensor is calibrated and the deformation of sensor is measured by light reflection. Then the micro friction is obtained by analyzing data. The results of experiment show the resolution of specification of micro friction testing is 10μN, which could meet the demands of micro friction testing with short stroke and high resolution and realize the precise test of micro friction, and the same time it has been analysed which load is unstable during testing.

A Magnetic Microsensor with Temperature Compensation Based on Optical Mechatronic Technology

An optical mechatronic magnetic microsensor with temperature compensation based on fiber Bragg grating (FBG) and microelectromechanical system (MEMS) technologies is demonstrated. Parallel nickel-electroplated cantilever beams are fabricated as an attractive bending mechanism for pushing the optical fiber. Related stress induced cantilever bend caused by magnetic force driving reflective wavelength shift that exactly corresponds with photo-elastic coupling effect to characterize microsensors. Two different cycles of gratings in the same fiber have fabricated to perform the function of magnetic sensing and temperature compensation for reducing temperature-induced bias in magnetic measurement automatically. The sensitivity of 2.238 T/nm with null temperature response has obtained which excited by Nd-Fe-B magnets with residual magnetic strength up to 1.26 Tesla.

Batch fabrication of cantilever array aperture probes for scanning near-field optical microscopy

We have developed a novel batch fabrication process for cantilever array aperture probes used in scanning near-field optical microscopy (SNOM). The array probes, consisting of 16 parallel cantilevers with each tip having an identical aperture, are proposed to dramatically reduce the scanning time for imaging or increase the throughput of near-field optical microscopy and lithography. In this study, apertures are defined by direct-write electron beam lithography and subsequent pattern transfer by reactive ion etch. Better quality and reproducibility of apertures are demonstrated through optical throughput measurement of the probes. The fabrication of apertures having complex shapes is also demonstrated. The process includes such novel elements as the use of local oxidation of silicon and the use of an aluminium – compatible release etch. The process has demonstrated very high yield with a measured reproducibility of aperture diameter of 5 nm. Thermal oxide cantilevers allow the use of the probes at wavelengths as short as 250 nm.