Flexible Shear Sensor Based on Embedded Optoelectronic Components

Abstract

Tactile shear stresses play an important role in the medical field and robotics. To monitor these stresses in situ, there is a need for unobtrusive flexible sensors that can be wrapped around curved surfaces or moving body parts. The presented sensor is based on changing coupling of optical power between a verticalcavity surface-emitting laser (VCSEL) and a photodiode facing each other and separated by a deformable transducer layer. The required optoelectronic components were embedded in a polymer foil of only 40 m thick, yielding a very thin and flexible total sensor stack of 250 m thick. In the linear part of the range (between 2 and 5.5 N), the sensitivity of the prototype was 350 A/N; the maximum measurable force was 5.5 N. However, by selecting the appropriate deformable sensor transducer material, the sensitivity and range can be tuned for a specific application.

Shear stress sensing with Bragg grating-based sensors in microstructured optical fibers

“…Current developments of shear stress sensors are based on MEMS technology [21], including piezo-resistive [22] or capacitive [23,24] shear stress sensors. More recently, Missine et al [25] demonstrated an optoelectronic shear sensor based on measuring the optical power with a photodiode received from a vertical cavity surface-emitting laser facing the photodiode and separated with a deformable transduction layer. Distributed shear force sensing was also proposed by Wang et al [26] using an array of optical fibers embedded in a flexible polymer foil.…”

Photonic Incremental Pressure Sensor Based on Optical Feedback in a Polymer Embedded VCSEL

“…After aligning the reflecting layers with the VCSEL active areas, both packages were brought into contact, creating an irreversible bond and a total transducer layer thickness of 100 μm. A similar approach can be used to create other types of sensors measuring other parameters such as shear force [6].…”

Unobtrusive packaging of optoelectronic devices for optical tactile and shear sensors

“…This is described above in more detail. To construct the sensor, an additional 100 μm thick layer of PDMS was spincoated and the mirror layer was bonded on top [4]. To characterize and read out the integrated sensor, a dedicated set-up was built, consisting of an automated force applying set-up allowing displacements in x, y and z directions with an accuracy of a few μm.…”

“…First, a 90 μm thick layer of PDMS was spin-coated on top of this foil and subsequently cured on a hot plate at 60°C for 1 h.. Then, photodiode and VCSEL foil package were cut-out from the temporary glass carrier using CO 2 laser ablation [4]. The sensor response to both displacement and related shear stress were measured using a Dage Series 4000 bondtester.…”