Pressure and shear sensing based on microstrip antennas

Abstract

A foot ulcer is the initiating factor in 85% of all diabetic amputations. Ulcer formation is believed to be contributed by both pressure and shear forces. There are commercially available instruments that can measure plantar pressure. However, instruments for plantar shear measurement are limited. In this paper, we investigate the application of antenna sensors for shear and pressure measurement. The principle of operation of both antenna sensors will be discussed first, followed by detailed descriptions on the antenna designs, sensor fabrication, experimental setup, procedure and results. Because the antenna sensors are small in size, can be wirelessly interrogated, and are frequency multiplexable, we plan to embed them in shoes for simultaneous mapping of plantar shear and pressure distributions in the future.

Insole Optical Fiber Sensor Architecture for Remote Gait Analysis—An e-Health Solution

“…For the calibration of the FBGs cell to F S , a metal slide, placed between the sensing units and a metal cylinder bar (3 kg), was horizontally dragged with the help of a translation stage [7], as shown in Fig. 2.…”

“…In 2013, Zhang et al used a similar method to produce a sensor for the measurement of the same parameters. However, in this case only two optical fibers with FBGs were used (one on the horizontal and the other on the diagonal directions), embedded in a soft polydimethylsiloxane matrix [7]. The sensitivities were found to be 0.82 pm/Pa for vertical pressure and 1.33 pm/Pa for shear.…”

“…2, the sensor was tested for simultaneous F S and F V loadings. The Bragg wavelength shifts, modulated in the optical fiber sensors under simultaneous shear and vertical loadings, can be related to the applied forces by a twoequation system [7] where ∆λ FBG1 and ∆λ FBG2 are the Bragg wavelength shift of FBG1 and FBG2, respectively. In Fig.…”

“…The proposed architecture comprises a compact and accurate biaxial OFS based on two in-line FBGs (FBG1 and FBG2), placed individually in two adjacent cavities. For the demodulation of the optical signal registered by the designed optical sensing cell, a system of two equations was used, correlating the sensitivities of both FBGs with the vertical (F V ) and shear (F S ) forces [7]. Moreover, we also present the design and integration of the sensing architecture in an insole for continuous monitoring of F S and F V (from which is calculated the plantar pressure), during the gait movement of patients.…”

Antenna Sensors in Passive Wireless Sensing Systems

“…All these antenna sensors are based on the same principle, i.e., the applied strain changes the dimension of the antenna radiation element and thus causes a shift of the antenna resonant frequency. A different principle was exploited by Bhattacharyya et al (2009) and Mohammad and Huang (2012a) for displacement and pressure sensing. In Bhattacharyya et al (2009), an RFID tag antenna was placed below a metallic plate.…”