Photothermal excitation of a single-crystalline silicon cantilever for higher vibration modes in liquid

Abstract

The authors analyze photothermal excitation of a single-crystalline silicon cantilever for higher vibration modes in liquid. The cantilever is bent by thermal stress generated by thermal diffusion in the direction perpendicular to the cantilever surface. Because the cantilever is made of a homogeneous material, thermal diffusion in the longitudinal direction does not generate thermal stress. Therefore, the higher vibration modes having small spatially periodic mode shapes are easily and effectively excited. The authors compared the excitation efficiency of two optical wavelengths, 405 and 780 nm. The 405 nm laser-diode beam was found to be 2.3-4.2 times more effective in exciting the second flexural mode compared with the 780 nm beam. These differences in excitation efficiency are attributed to the absorbance characteristics of silicon and were confirmed by measuring the transmitted light power ͑lost power͒ against the incident light power. Vibration amplitude of each mode was sufficient to operate dynamic-mode atomic force microscopy in liquid.

High efficiency laser photothermal excitation of microcantilever vibrations in air and liquids

“…Figure 2 shows the response of the uncoated trapezoidal and rectangular cantilevers as the excitation laser is swept across the width. Many previous studies 4,5,8,9,16 of photothermal excitation of cantilevers (one-dimensional models) implicitly assume that this signal should be approximately flat through the middle of the cantilever and fall off toward the edges (where some of the laser light starts to fall off the cantilever), and this result has also been demonstrated in experiments. 17 This is exactly the response shown by the rectangular cantilevers.…”

“…5,8 However, it is also possible to use plain, uncoated silicon cantilevers. 9 Here, thermal gradients through the cantilever thickness creates a bending moment. 10 For some cases, radiation pressure 8 and electronic strains 12 may also contribute to the moment.…”

“…For uncoated cantilevers or longer wavelength lasers, efficiency may be one or two orders of magnitude worse. 9 Because the efficiency is low, the input power must be high. However, this may be undesirable for two reasons.…”

Role of the driving laser position on atomic force microscopy cantilevers excited by photothermal and radiation pressure effects

“…[1][2][3] In particular, recent advances in the field are based on resonating cantilevers actuated by photothermal and pressure radiation effects elicited by a laser focused on the back of the cantilever itself. [4][5][6] This approach has been applied both for force spectroscopy experiments on single molecules 7 and for high speed atomic force microscopy imaging. 8 The extension and optimal application of this actuation strategy requires a complete knowledge of the cantilever dynamics; whereas some work has been done on the frequency dependence of the photothermal actuation in a fluid, 9,10 only few indications are reported about the influence of the driving laser position on the cantilever dynamics.…”

Application of a new microcantilever biosensor resonating at the air–liquid interface for direct insulin detection and continuous monitoring of enzymatic reactions

“…The signal was recorded with a sampling rate of 10 Hz, and a frequency drift of the system was below 100 Hz. 26,27 The liquid was introduced by a push/pull syringe pump (KD scientific, KD270) connected to both sides of the microchannel in order to stabilize the liquid pressure on the cantilever. In addition, the new bio-solution was loaded in an injector placed between the pump and the inlet of the microchannel (Fig.…”