Sensors cantilever

Cantilever sensors have been shown to detect changes in surface tension ligand-receptor binding and molecular conformation. 

Mass-produced cantilever sensors, however, have the potential to satisfy the conditions of selectivity, sensitivity, miniature size, low power consumption, and real-time operation [5, 6], Microcantilevers are micromachined from silicon or other materials and can easily be fabricated in multiple-element arrays. They resemble miniature diving boards measuring 100 to 200 pm long by about 20 to 40 pm wide by 0.3 to 1 pm thick and having a mass of a few nanograms. Their primary advantage originates from their sensitivity, which is based on the ability to detect their motion with subnanometer precision. 

Producing highly calibrated, trace quantities of explosive vapor is a challenging task. As the vapor pressures of most explosives are extremely small at room temperature, their vapors are often produced by maintaining the sources at higher temperatures. This leads to the condensation of vapor at cold spots, which should be avoided to deliver highly calibrated quantities of explosive vapors to the cantilever sensor. 

In contrast to SPFS, SPR, and SPDS are tools that can study biomolecular interactions without external labels. They share the same category of label-free biosensors with the reflectometry interference spectroscopy (RIfS) [46], waveguide spectroscopy [47], quartz crystal microbalance (QCM) [48], micro-cantilever sensors [49], etc. Although the label-free sensors cannot compete with SPFS in terms of sensitivity [11], they are however advantageous in avoiding any additional cost/time in labeling the molecules. In particular, the label-free detection concept eliminates undue detrimental effects originating from the labels that may interfere with the fundamental interaction. In this sense, it is worthwhile to develop and improve such sensors as instruments complementary to those ultra-sensitive sensors that require labels. 

Campbell, G. A., Mutharasan, R Escherichia coli 0157 H7 detection limit of millimetersized PZT cantilever sensors is 700 cells/mL. Analytical Sciences 2005,21 (4), 355-357... 

Campbell, G.A., Medina, M. B., Mutharasan, 1C Detection of Staphylococcus enterotoxin B at picogram levels using piezoelectric-excited millimeter-sized cantilever sensors. Sensors and Actuators B Chemical 2007, 126 (2), 354-360... 

Rijal,K., Mutharasan,R. Piezoelectric-excited millimeter-sized cantilever sensors detect density differences of a few micrograms/mL in liquid medium. Sensors and Actuators B Chemical2007, 121 (1), 237-244... 

Wilson, T. L., Campbell, G. A., Mutharasan, R. Viscosity and density values from excitation level response of piezoelectric-excited cantilever sensors. Sensors and Actuators A Physical 2007, 138 (1), 44-51... 

Campbell, G. A., Mutharasan, R. Monitoring of the self-assembled monolayer of 1-hexa-decanethiol on a gold surface at nanomolar concentration using a piezo-excited millimeter-sized cantilever sensor. Langmuir 2005, 21 (25), 11568-11573... 

Campbell, G. A., Mutharasan, R. Use of piezoelectric-excited millimeter-sized cantilever sensors to measure albumin interaction with self-assembled monolayers of alkanethiols having different functional headgroups. Analytical Chemistry 2006, 78 (7), 2328-2334... 

Keywords Cantilever sensors, explosive vapour detection, resonance frequency,... 

Reed J, WUMnson P, Schmit J, King W, Gimzewski JK et al. (2006) Observation of nanoscale dynamics in cantilever sensor arrays. Nanotechnology. 17 3873-3879. 

One of the most significant aspects of the cantilever sensor is that the adsorption-induced cantilever bending is not affected by operation in solution. We were able to detect the Cs ion at concentrations as small as 10 M in solution using the cantilever deflection method. This corresponds to a coverage of 4 X 10" monolayers ... 

We have demonstrated an extremely sensitive sensor platform for groundwater monitoring. The sensitivity of the cantilever sensor depends on cantilever dimension, while the selectivity depends on die selectivity of the surface coating for chemical interactions. Research is underway to develop cantilever arrays for simultaneous multi-analyte detection. The primary advantages of the microcantilever method are (1) the sensitivity of microcantilevers based on their ability to detect cantilever motion with subnanometer precision (2) their ability to be fiibricated into multi-element sensor arrays and (3) their ability to work in a liquid environment. 

Flow Rate Measurements, Methods, Fig. 21 Optical response of the fiber cantilever sensor to various volumetric... 

Mechanical nanosensors possess comparative advantages over optical nanosensors and electromagnetic nanosensors for the measurement of nanoscale mechanical properties [2]. Examples of mechanical nanosensors include CNT-based fluidic shear-stress sensors [3] and the nanomechanical cantilever sensors [4]. 

Liu YF, Wang WX, Shu WM (2011) Chapter 3 Nanomechanical cantilever sensors theory and applications. In Lim TC (ed) Nanosensors theory and applications in industry, healthcare and defense. CRC Press, Boca Raton, pp 69-96... 

A nanomechanical sensor is a mechanical structure that transduces analyte-induced stimuli into a signal via its structural change with nanometer precision. The definition of a nanomechanical sensor can also cover a mechanical transducer with nanometer scale. In either sense, a cantilever sensor is a representative example among various geometries. 

As demonstrated by various groups, nanomechanical sensors are applicable to a wide variety of targets. To take advantage of their attractive feature, it is important to understand the basics of nanomechanical sensors. In the following sections, we will briefly review working principles and readout methods of cantilever sensors [10]. Then, recent developments in the field of nanomechanical sensing will be highlighted. 

Cantilever sensors can detect the following two physical parameters volume and/or mass of target molecules. Since all substances have volume and mass, we can measure almost any kind of substance by using cantilever sensors. To measure volume and mass of target molecules, there are basically two operation modes of cantilever sensors static mode and dynamic mode (Fig. 4.3.1). Details will be described in the following sections. 

For solid coating layers, a simple analytical model is proposed. It provides general reference values in terms of the strain induced in the coating layer [11,12]. It will help toward analyzing the static behavior of cantilever sensors and various nanomechanical sensors in conjunction with physical properties of coating films as well as optimizing the films for higher sensitivity. The details of the analytical model will be discussed later. 

There are several readout methods to record responses of cantilever sensors [1]. In this section, we will introduce two representative readout methods optical readout with a laser and electrical readout with a piezoresistor. 

To consider the effect of a receptor layer, Timoshenko beam theory, which was originally developed to analyze a bimetal strip, can be used [38]. Based on the Timoshenko beam theory, an analytical model for the static deflection of a cantilever sensor coated with a solid layer was derived. In a simple cantilever coated with a solid receptor layer as shown in Fig. 4.3.10, the deflection of the cantilever is described as ... 

Analytes adsorbed/absorbed on a cantilever sensor can induce two-dimensional stress on the surface of the receptor layer (type A) or on the interface between the receptor layer and the cantilever (type B) as depicted in Fig. 4.3.11. The type A stress is induced when the surface of a cantilever is modified by functional groups including self-assembled monolayers. Analytes that induce charge distribution at the interface by dipole interactions can cause the type B stress. Here, we focus on these two cases [12]. 

The deflection of a cantilever sensor is investigated by FEA simulation. The length, width, and thickness of the cantilever are set at 500, 100, and 1 pm, respectively. The results are depicted in Fig. 4.3.11c and d. The deflection is plotted as a function of thickness. As we have seen in the previous section, the deflection increases by decreasing the Young s modulus for the type A stress. There is an optimal thickness f,.op written as Eq. (4.3.7). The... 

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