Bending cantilever beam measurement method

The piezoresistive readout technique has several advantages over commonly used optical beam deflection methods. For example, optical beam deflection probes the bending of the free end of the cantilever. It is assumed that the bending is uniform along the length of the cantilever. The piezoresistive method, however, measures the integrated bending of the cantilever. Piezoresistive cantilevers can be encapsulated in silicon nitride... 

In most cases the variation in surface stress has been determined indirectly by measuring the potential dependence of the strain (i.e., electrode deformation) and then obtaining the variation in stress from the appropriate form of Hookes law (-> bending beam or cantilever beam method, bending plate methods e.g., the measurement of the deformation of the electrode with the help of a —r Kosters laser interferometer). 

Several methods have been described for measuring the bending modulus of hbers. The balanced hber method of Scott and Robbins [73,74] appears to be the easiest to handle experimentally (except for very curly hair) and provides less scatter than the other methods [74], The vibrating-reed method (oscillating hber cantilever) has also been used with human hair [10], The cantilever beam method [75], the loop deformation method [76], and the center load beam method [76] have been described for textile hbers. 

In the previous methods, the use of a continuous membrane for measuring cell forces has the disadvantage that the traction forces are convoluted by the observed bead displacements. Because the calculation is not direct, constraints or assumptions are required to solve the inverse problem. A technique to transduce individual traction forces comes from the use of microfabricated cantilevers. The first demonstration of these sensors was a horizontal silicon cantilever that was made with microfabrication techniques (Figure 22.6a). As a cell migrates across the surface, it bends the cantilever under the load of the traction force. Because the sensor is mechanically decoupled from the substrate, the deflection of the cantilever directly reports only the local force. The simple spring equation relates the deflection of the cantilever beam 8 to the cellular traction force ... 

Biosensors Using Lasers, Fig. 7 Scheme of the optical readout method for a microcantilever bending evaluation. The displacement of the free end of the cantilever is measured by monitoring the optical deflection of an incident laser beam on a position-sensitive detector... 

Cantilever-beam stiffness n. A method of determining stiffness of plastics by measuring the force and angle of bend of a cantilever beam made of the specimen material. The ASTM test is D747. 

This test method can be used to measure the relative susceptibility of materials by "Determining the Threshold Stress Intensity Factor for Environment-Assisted Cracking EAC of Metallic Materials. Constant load specimens, both the fatigue precracked single edge beam SE(B) and precracked compact specimens are tested in bending. The SE(B) was originally referred to as the Cantilever Beam Test. 

The tensile strength and stress of the IPMC are measured in the same manner as those of the IP. The bending stiffness of a fully hydrated IPMC sample is estimated using the free oscillation attenuation method. By bending the sample to the appropriate initial displacement, the free vibration response can be recorded. The natural frequency of the cantilever, is obtained from the fast Fourier transform of the free vibration response curve. The stiffness of the IPMC, Egg, is determined using Eq. 4, which is based on the thin cantilever beam theory of material mechanics ... 

The most commonly used direct method for determination of surface stress is the bending beam method in which a lever bends when subjected to a change in surface stress in one of its faces in order to minimize its stored strain energy. The relationship between the deflection of a cantilever and the different stresses in its smfaces was first determined by Stoney [25] and in surface science it has been used to measure the stress changes associated with the reconstructions of semiconductor surfaces [26 - 27]. 

The electrocapillary curve of a solid metal electrode is more difficult to measure than that of a liquid electrode, because of problems of surface cleanliness. The most widely used approach has been the bending-beam method, which was originally developed by Fredlein et al. [28] using large samples. More recently Raiteri and Butt [29] have used gold electrodes deposited on an AFM cantilever to record electrocapillary curves. 

In the simplest version of AFM, called contact mode or normal force mode, the tip is brought into hard contact with the sample surface such that the cantilever bends due to the tip-sample repulsion (Fig. 3A). The cantilever deflection can be measured in several ways, but the most common is the optical beam method. In this approach, a laser beam from a semiconductor laser is focused on the back side of the cantilever, as shown in Fig. 2A. The reflected light hits a position-sensitive detector that produces a voltage indicating how much the cantilever has deflected up or down. In some cases, the detector also produces a... 

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