Since the late 1980s there have been spectacular developments in micromechanical or microelectro-mechanical (MEMS) systems which have enabled the exploration of transduction modes that involve mechanical energy and are based primarily on mechanical phenomena. As a result an innovative family of chemical and biological sensors has emerged. In this article, we discuss sensors with transducers in a form of cantilevers. While MEMS represents a diverse family of designs, devices with simple cantilever configurations are especially attractive as transducers for chemical and biological sensors. The review deals with four important aspects of cantilever transducers: (i) operation principles and models; (ii) microfabrication; (iii) figures of merit; and (iv) applications of cantilever sensors. We also provide a brief analysis of historical predecessors of the modern cantilever sensors.

Cantilever transducers as a platform for chemical and biological sensors

The interferon regulatory factor (IRF) family, consisting of nine members in mammals, was identified in the late 1980s in the context of research into the type I interferon system. Subsequent studies over the past two decades have revealed the versatile and critical functions performed by this transcription factor family. Indeed, many IRF members play central roles in the cellular differentiation of hematopoietic cells and in the regulation of gene expression in response to pathogen-derived danger signals. In particular, the advances made in understanding the immunobiology of Toll-like and other pattern-recognition receptors have recently generated new momentum for the study of IRFs. Moreover, the role of several IRF family members in the regulation of the cell cycle and apoptosis has important implications for understanding susceptibility to and progression of several cancers.

The IRF Family Transcription Factors in Immunity and Oncogenesis

https://imechanica.org/files/cammarataPSS1994.pdf

Surface and interface stress effects in thin films

The merging of silicon microfabrication techniques with surface functionalization biochemistry offers new exciting opportunities in developing microscopic biomedical analysis devices with unique characteristics. Micro-mechanical transducers for chemical and biosensing applications represent one possibility. Microcantilevers can transduce a chemical signal into a mechanical motion with high sensitivity. In this review we summarize how cantilever-based sensors can be operated, and their working principle is presented in few selected biosensing experiments which have been performed recently in our groups in the study of biotin–streptavidin and antigen–antibody interactions, and specific surface charge development of organic molecules. We also discuss the advantages of this novel technique as well as its potentials.

Micromechanical cantilever-based biosensors

The role of surface stress in reconstruction, epitaxial growth and stabilization of mesoscopic structures

Mesure des contraintes internes d'une surface propre Si(111)7×7 par comparaison avec une surface de reference sur laquelle est adsorbee une couche monomoleculaire de Ga sous ultravide

/pdf/direct-measurement-of-crystal-surface-stress-3ivrzklp5a.pdf

Direct measurement of crystal surface stress.

ICSBP (IRF-8) is a transcription factor of the IRF family expressed only in the immune system. It is induced in macrophages by gamma interferon (IFN-γ) and contributes to macrophage functions. By interacting with Ets family protein PU.1, ICSBP binds to the IRF/Ets composite element and stimulates transcription. ICSBP binds to another DNA element, the IFN-stimulated response element (ISRE), a common target of the IRF family. Limited knowledge as to how ICSBP and other IRF proteins regulate ISRE-dependent transcription in IFN-γ-activated macrophages is available. By mass-spectrometric analysis of ISRE-bound proteins in macrophages, we identified TEL, another Ets member, as a factor recruited to the element in an IFN-γ-dependent manner. In vitro analysis with recombinant proteins indicated that this recruitment is due to a direct interaction between ICSBP and TEL, which is enhanced by the presence of ISRE. Significantly, the interaction with TEL in turn resulted in the recruitment of the histone deacetytase HDAC3 to the ISRE, causing increased repression of IFN-γ-mediated reporter activity through the ISRE. This repression may provide a negative-feedback mechanism operating after the initial transcriptional activation by IFN-γ. By associating with two different Ets family proteins, ICSBP exerts a dual function in IFN-γ-dependent gene regulation in an immune system-specific manner.

Gamma Interferon Triggers Interaction between ICSBP (IRF-8) and TEL, Recruiting the Histone Deacetylase HDAC3 to the Interferon-Responsive Element

High coverage phases of Pb on the Si(111) surface: structures and phase transitions

High quality homoepitaxial growth of Si on Si(111) through an overlayer of Au is shown to occur at 450–500 °C, far below the temperature required for growth of Si of similar quality on bare Si(111). Films of unlimited thickness can be obtained with excellent crystalline quality, as revealed by Rutherford backscattering spectrometry ion channeling measurements (χmin=2.2%). A distinct range of Au coverage (0.4–1.0 monolayer) results in the best quality epitaxy, with no measurable amount of Au trapped at either the interface or within the grown films. Cross‐sectional transmission electron microscopy reveals that in films grown with Au coverages below and above the optimum range, the predominant defects are twins on (111) planes and Au inclusions, respectively.

/pdf/low-temperature-homoepitaxial-growth-on-si-111-mediated-by-47e8rglcyy.pdf

Low‐temperature homoepitaxial growth on Si(111) mediated by thin overlayers of Au

We have measured extremely large anisotropic thermal vibrations of gallium adatoms on a Si(111) surface using x-ray standing waves. At 830 K the rms amplitude normal to the surface is 0.47{plus minus}0.02 A while the parallel amplitude is 0.30{plus minus}0.02 A. The temperature dependence of these amplitudes deviates significantly from that expected from Debye theory and suggests a significant thermal softening of the surface bonding at elevated temperatures.

/pdf/giant-vibrations-of-impurity-atoms-on-a-crystal-surface-4an0ylqyhu.pdf

Robert E. Martinez

Papers

Direct measurement of crystal surface stress.

Gamma Interferon Triggers Interaction between ICSBP (IRF-8) and TEL, Recruiting the Histone Deacetylase HDAC3 to the Interferon-Responsive Element

High coverage phases of Pb on the Si(111) surface: structures and phase transitions

Low‐temperature homoepitaxial growth on Si(111) mediated by thin overlayers of Au

Giant vibrations of impurity atoms on a crystal surface.