Unconventional Uses of Microcantilevers as Chemical Sensors in Gas and Liquid Media

The use of microcantilevers as (bio)chemical sensors usually involves the application of a chemically sensitive layer. The coated device operates either in a static bending regime or in a dynamic flexural mode. While some of these coated devices may be operated successfully in both the static and the dynamic modes, others may suffer from certain shortcomings depending on the type of coating, the medium of operation and the sensing application. Such shortcomings include lack of selectivity and reversibility of the sensitive coating and a reduced quality factor due to the surrounding medium. In particular, the performance of microcantilevers excited in their standard out-of-plane dynamic mode drastically decreases in viscous liquid media. Moreover, the responses of coated cantilevers operating in the static bending mode are often difficult to interpret. To resolve these performance issues, the following emerging unconventional uses of microcantilevers are reviewed in this paper: (1) dynamic-mode operation without using a sensitive coating, (2) the use of in-plane vibration modes (both flexural and longitudinal) in liquid media, and (3) incorporation of viscoelastic effects in the coatings in the static mode of operation. The advantages and drawbacks of these atypical uses of microcantilevers for chemical sensing in gas and liquid environments are discussed

Unconventional Uses of Cantilevers for Chemical Sensing in Gas and Liquid Environments

Microcantilevers used as (bio)chemical sensors are usually coated with a chemically sensitive layer. The coated devices operate either in a static bending regime or in a dynamic flexural mode. While the coated devices operate generally well in both the static and dynamic mode, they do suffer from certain shortcomings depending on the medium of operation and the application, including lack of selectivity and of reversibility of the sensitive coating and a reduced quality factor due to the surrounding medium. In particular, the performance of microcantilevers excited in their standard out-of-plane dynamic mode drastically decreases in viscous liquid media. Moreover, the responses of coated cantilevers operating in the static bending mode are often difficult to interpret. To resolve those performance issues, unconventional uses of microcantilever are reviewed in this paper, which consist of the use of the dynamic mode without sensitive coating, the use of in-plane (flexural and longitudinal) vibration modes in liquid media, and fully accounting for the viscoelastic effects of the coatings in the static mode of operation. The advantages and drawbacks of these unconventional uses of microcantilevers for chemical sensing in gas and liquid environments are discussed

ÉTUDE PAR EFFET MÖSSBAUER DES CHAMPS MAGNÉTIQUES TRANSFÉRÉS SUR LE NOYAU DE 119Sn4+ DANS FeF3

Un échantillon de FeF3 dopé par 119Sn4+ a été examiné par spectroscopie Mössbauer. Le transfert de densité de spin dans les orbitales de l'étain a été observé, le champ magnétique résultant a pour valeur 129 kOe à 77 K. Une comparaison de paramètres Mössbauer de 119Sn4+ dans FeF3 avec ceux obtenus par des auteurs antérieurs pour 119Sn4+ dans Y0,9Ca0,1Fe0, 9Sn0,1O3 suggère un renforcement de la polarisation de spin de la charge électronique des orbitales 5s de Sn+4 dans le cas de la matrice fluorée.A sample of FeF3 doped with 119Sn4+ was investigated by Mössbauer spectroscopy. A transfer of spin density was observed in the orbitals of tin with resulting magnetic field H(0)77K = 129 kOe. The comparison of the Mössbauer parameters of 119Sn4+ in FeF3 with those obtained by previous authors for 119Sn4+ in Y0.9Ca0.1Fe0.9Sn0.1O3 suggests a growing spin polarization of the electronic charge in the 5s orbitals of Sn4+ in the FeF3 matrix