A Low Cost Inkjet-Printed Mass Sensor Using a Frequency Readout Strategy

The development of low-cost mass sensors is of unique interest for the scientific community due to the wide range of fields requiring these kind of devices. In this paper, a full inkjet-printed mass sensor is proposed. The device is based on a PolyEthylene Terephthalate (PET) cantilever beam (operating in its first natural frequency) where a strain-sensor and a planar coil have been realized by a low-cost InkJet Printing technology to implement the sensing and actuation strategies, respectively. The frequency readout strategy of the sensor presents several advantages, such as the intrinsic robustness against instabilities of the strain sensor, the residual stress of the cantilever beam, the target mass material, and the distance between the permanent magnet and the actuation coil (which changes as a function of the target mass values). However, the frictionless actuation mode represents another shortcoming of the sensor. The paper describes the sensor design, realization, and characterization while investigating its expected behavior by exploiting dedicate models. The working span of the device is 0–0.36 g while its resolution is in the order of 0.001 g, thus addressing a wide range of potential applications requiring very accurate mass measurements within a narrow operating range.

An Extensive Review of Nanotubes Based Mass-Sensors

Sensors have tremendous demand in Industry because of their properties like sensitiveness, responsiveness, stability, selectiveness, and cost-effectiveness. Therefore, it is a dire need to develop advanced sensing materials and technologies. With the rapid advancement in micro and nanotechnologies in Micro-electromechanical Systems/ Nano-electromechanical Systems (MEMS/NEMS), more emphasis has to develop micro and nanomechanical resonators, having great interest for engineering fields. When MEMS/NEMS resonators are used for advancement in sensors, then they could perform both detection and sensing. Both BNNT and CNT are the strongest lightweight nanomaterials used for mass sensing applications. BNNT contradict to CNT have nontoxic property towards health and environment because of its structural stability and chemical inertness, which makes it more suitable for biological applications. From various studies, the conclusion comes out that the non-linear dynamic behavior of Boron Nitride Nanotubes-based mass sensors has not yet been explored. It is required strongly to study the non-linear conduct of BNNT for designing a better performing mass sensor.

A High-Resolution Fully Inkjet Printed Resonant Mass Sensor

The rapid prototyping of low-cost sensors is assuming strategic importance in several application fields. In this paper, a fully inkjet printed mass sensor is proposed. The device consists of a poly-ethylene terephthalate (PET) cantilever beam, which is driven to its resonant mode by an electromagnetic actuation mechanism, implemented through the interaction between a current impulse flowing through a planar coil (inkjet printed on the PET beam), and a permanent magnet, facing the actuation coil. Target masses are positioned close to the beam end. The sensing methodology, based on the relationship between the beam first natural frequency and the target mass, is implemented through a strain gauge (inkjet printed across the fixed end of the cantilever). The resonant operating mode of the sensor confers intrinsic robustness against instabilities of the strain sensor structure (e.g., the residual stress of the cantilever beam), the target mass material and the magnet–coil distance. The latter indeed changes as a function of the target mass values. The friction-less actuation mode is another shortcoming of the sensor, as well as the low-cost feature arising from the adopted technology. As far as we know, the solution proposed is the first example of a low-cost fully printed mass sensor. The operating range of the device is 0–0.36 g while its resolution is in the order of 1.0 mg, thus addressing crucial application fields. A Q factor around 35 has been estimated, which confirms the suitable performances of the sensor in term of selectivity and resolution.