Parametric evaluation of shear sensitivity in piezoresistive interfacial force sensors

Abstract

A three-axis load detector has been designed and manufactured utilizing four piezoresistive sensors on a flexible silicon membrane. The detector was prototyped using bulk microfabrication techniques on a single-crystal silicon wafer and was designed to detect normal and shear loadings applied to the membrane. Finite element analysis and experimental calibration methods have been used to determine the shear and normal sensitivity values. Device parameters were modified with emphasis on increasing the absolute shear to normal sensitivity ratio of the sensors without reducing their ultimate strength. It was determined that the shear to normal sensitivity ratio greater than 0.5 would allow detection of shear loads considering experimental error present. For devices with square membranes having 1000 µm edge lengths and 65 µm thicknesses, this amount of shear sensitivity was achievable using a mesa with a height of at least 150 µm.

Design and calibration of a six-axis MEMS sensor array for use in scoliosis correction surgery

“…Following photolithography, the TSVs were filled with conductive adhesive and the mesas (shear transmission structures) were manually adhered to the top surface of the membranes. Further details on the microfabrication process and verification of sensor pad performance were presented in previous work [25]. The fabricated device has been shown structurally in figure 4.…”

“…These devices generally make use of varying stress distribution patterns to detect applied multi-axis loads, integrating the piezoresistive elements to produce voltage outputs corresponding to the stresses at significant regions. Applications for multi-axis sensors include tactile sensing [10,14,16,19,20], robotics [13,14,20,21], and biomedical or biomechanical applications [11,[22][23][24][25][26][27]. Regardless of the application, the nature for the calibration of devices should utilize calibration forces and moments which are similar in magnitude and application method to the loads that the sensors will detect in the field.…”

A packaging solution utilizing adhesive-filled TSVs and flip–chip methods

“…The wireless and power components were also custom designed and modular. More information on the sensors [28] and wireless and power components [28][29][30] is provided in previous work. Connectivity between components was made using a FPCB which could be wrapped around the head of a spinal screw.…”

Tooth-Inspired Tactile Sensor for Detection of Multidirectional Force

“…For MIS application, a small-scale sensor inspired by a hair cell was made, with a diameter of only 420 μm [28], a detectable shear force range below 5 mN, and a post’s maximum displacement of only 15 μm. Building a mesa structure [29] or a probe [30] on a flat sensor element was proven to increase the detectable shear force range. All of these sensors are similar to our proposed sensor in the use of a protruding structure, such as pole, post, probe, or mesa structure.…”