A microfluidic tactile sensor based on a diaphragm pressure sensor design

(Nanowerk News) In a new paper in Advanced Materials ("Wearable Microfluidic Diaphragm Pressure Sensor for Health and Tactile Touch Monitoring"), researchers report a microfluidic tactile sensor based on a diaphragm pressure sensor design.
The development of flexible pressure sensors has various potential applications in soft robotics, wearable electronics, and artificial electronic skins.
Microfluidic tactile diaphragm pressure sensor
Microfluidic tactile diaphragm pressure sensor. a) Optical image of a finished microfluidic diaphragm sensor. b) Schematic layout of the diaphragm sensor and c) the equivalent circuit schematic forming an equivalent Wheatstone bridge circuit. d) Simulation of the normal stress for the radial sensing grids (?r) (along X-axis) and the normal stress for the tangential sensing grids (σt) (along Y-axis) of the sensor under 1 kPa pressure applied over a 9 mm diameter and e) a schematic diagram indicating testing conditions. (© Wiley-VCH Verlag) (click on image to enlarge)
This novel diaphragm pressure sensor design utilizing an embedded equivalent Wheatstone bridge circuit makes the most of tangential and radial strain fields, allowing the researchers to achieve a combination of high sensitivity, linearity, low limit of detection, high resolution, and temperature self-compensation.
The usage of the Wheatstone bridge design also provides built-in temperature compensation allowing for operation between 20 and 50°C without external offsets.
Due to its performance, the diaphragm pressure sensor meets the requirement of a variety of potential applications. Among many, one feasible and effective health monitoring application is heart-rate monitoring.
As a proof of concept, the researchers designed and fabricated a PDMS wristband with an embedded microfluidic diaphragm pressure sensor to measure dynamic pulse measurements.
Tactile sensing glove
Tactile sensing glove. a) Photograph of hand-shaking wearing the PDMS tactile sensing glove. b) Schematic of the PDMS tactile sensing glove. c) Photograph of the tactile sensing glove worn while grasping a grape. d) Real-time response recorded from the corresponding thumb and index finger sensors for gently grasping and releasing the grape. e) Photograph of the tactile sensing glove worn while gripping a bat and the corresponding output voltage map across the sensors within the glove. (© Wiley-VCH Verlag) (click on image to enlarge)
"The detection limit of our sensor has been shown to be below 100 Pa with sub-50 Pa resolution," the authors note. "The extremely low detection limit and resolution combined with an ultrafast response time of 90 ms allows for the sensor to be used in a wide range of applications."
As the team demonstrates, the liquid-state diaphragm pressure sensors may be utilized as either standalone devices for monitoring pressure at a specific point or into large arrays for tactile mapping in a variety of electronic skin and smart textile applications for wearables, robotics, and beyond.
Michael Berger By – Michael is author of three books by the Royal Society of Chemistry:
Nano-Society: Pushing the Boundaries of Technology,
Nanotechnology: The Future is Tiny, and
Nanoengineering: The Skills and Tools Making Technology Invisible
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