A Dual-Axis Metamaterial BioNEMS Accelerometer for Biomedical Applications

In this article, a novel two-axis optical nano-electromechanical-system (NEMS) accelerometer based on metamaterials is presented for biomedical applications. This sensor consists of a proof mass with two different patterns of split-ring resonators (SRR) on its fingers to form a tunable metamaterial device. The fingers connected to the proof mass are movable, while the others are anchored to the sensor framework. In fact, in this structure, two separated parts of the metamaterial cells are coated on the movable and the fixed fingers that are coupled by a nanoscale air gap. When the accelerated proof mass is displaced by physical activities in the xy plane, the coupling of meta-arrays changes and the sensing wavelengths are thus varied. Detection of these changes leads to the measurement of body accelerations or position estimation occurred in different situations. The proposed BioNEMS accelerometer is then analyzed by numerical and analytical methods, which result in the functional characteristics of this platform as follows:
${x}$
-direction optical sensitivity of
${S}_{\text {ox}} =116$
nm/g,
${y}$
-direction optical sensitivity of
${S}_{\text {oy}} =88$
nm/g,
${x}$
-direction mechanical sensitivity of
${S}_{\text {mx}} =133.3$
nm/g,
${y}$
-direction mechanical sensitivity of
${S}_{\text {my}} =133.3$
nm/g, and measurement range of
${M}_{r} = \pm 20$
g for both directions and bandwidth of BW = 500 Hz. According to the results, the presented two-axis BioNEMS accelerometer can be a highly sensitive nanoscale platform for measuring accelerations in various medical applications, such as wearable devices (smartwatches or robot gloves), surgery robots, and medical imaging probes.