A Review on Theory and Modelling of Nanomechanical Sensors for Biological Applications

Abstract

Over the last decades, nanomechanical sensors have received significant attention from the scientific community, as they find plenty of applications in many different research fields, ranging from fundamental physics to clinical diagnosis. Regarding biological applications, nanomechanical sensors have been used for characterizing biological entities, for detecting their presence, and for characterizing the forces and motion associated with fundamental biological processes, among many others. Thanks to the continuous advancement of micro- and nano-fabrication techniques, nanomechanical sensors have rapidly evolved towards more sensitive devices. At the same time, researchers have extensively worked on the development of theoretical models that enable one to access more, and more precise, information about the biological entities and/or biological processes of interest. This paper reviews the main theoretical models applied in this field. We first focus on the static mode, and then continue on to the dynamic one. Then, we center the attention on the theoretical models used when nanomechanical sensors are applied in liquids, the natural environment of biology. Theory is essential to properly unravel the nanomechanical sensors signals, as well as to optimize their designs. It provides access to the basic principles that govern nanomechanical sensors applications, along with their intrinsic capabilities, sensitivities, and fundamental limits of detection.

Recent Advances in Nanomechanical Membrane-Type Surface Stress Sensors towards Artificial Olfaction

“…Then, many research groups have demonstrated that nanomechanical sensors can detect not only a variety of targets, such as moisture [ 41 , 42 , 43 ] and mercury vapor [ 41 , 44 ], but also various chemical/physical phenomena, including the formation of a self-assembled monolayer [ 45 ], DNA hybridization [ 46 , 47 , 48 ], a single spin [ 49 , 50 ], and quantum state [ 51 , 52 ]. Regarding the working principle of nanomechanical sensors whose flexible structures deform at the nanoscale, they are following two major types of operation modes: the static mode and dynamic mode [ 32 , 53 , 54 , 55 , 56 , 57 , 58 ]. In this section, we will briefly review these two operation modes.…”

“…The cantilever-type sensors can detect two physical parameters: volume and/or mass of target molecules. To measure the volume and mass of target molecules, there are two different operation modes as mentioned above: dynamic and static modes ( Figure 3 ) [ 32 , 53 , 54 , 55 , 56 , 57 , 58 ]. While the static mode detects changes in the deformation state of a nanomechanical sensor, the dynamic mode detects changes in the mechanical resonances.…”

“…Because of its high sensitivity, nanomechanical sensors in dynamic mode can be utilized for a new type of mass spectrometry known as nanomechanical mass spectrometry [ 26 , 28 , 61 , 64 , 65 , 66 , 67 , 68 , 69 ]. To improve the sensitivity further for the dynamic mode operation, various studies have reported, such as the use of other functional structures [ 32 , 43 , 70 , 71 , 72 ].…”

“…Among a wide variety of chemical sensors, nanomechanical sensors have received significant attention, as they find plenty of applications in many different research fields ( Figure 2 ) [ 11 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. In human olfactory perception, it is known that there are approximately 400 different kinds of olfactory receptors [ 34 ], which express wide varieties of chemical selectivity, providing unique patterns of odors.…”

“…In this context, nanomechanical sensors are one of the ideal sensing platforms for olfactory sensors because of its intrinsic versatility. According to their working principle, nanomechanical sensors detect volume- and/or mass-induced mechanical changes of a sensing element [ 32 ]. Since it has been observed that almost all kinds of solid materials, including organic small molecules, polymers, self-assembled nanomaterials, inorganic nanoparticles, and biomolecules, exhibit mechanical deformation upon gas sorption, various types of solid materials can be utilized as a receptor material, providing a wide range of chemical selectivity and sensitivity.…”