Abstract
There is a rapid growing demand for highly sensitive, easy adaptive and low-cost pressure sensing solutions in the fields of health monitoring, wearable electronics and home care. Here, we report a novel flexible inductive pressure sensor array with ultrahigh sensitivity and a simple construction, for large-area contact pressure measurements. In general, the device consists of three layers: a planar spiral inductor layer and ferrite film units attached on a polyethylene terephthalate (PET) membrane, which are separated by an array of elastic pillars. Importantly, by introducing the ferrite film with an excellent magnetic permeability, the effective permeability around the inductor is greatly influenced by the separation distance between the inductor and the ferrite film. As a result, the value of the inductance changes largely as the separation distance varies as an external load applies. Our device has achieved an ultrahigh sensitivity of 1.60 kPa−1 with a resolution of 13.61 Pa in the pressure range of 0–0.18 kPa, which is comparable to the current state-of-the-art flexible pressure sensors. More remarkably, our device shows an outstanding stability when exposed to environmental interferences, e.g., electrical noises from skin surfaces (within 0.08% variations) and a constant pressure load for more than 32 h (within 0.3% variations). In addition, the device exhibits a fast response time of 111 ms and a good repeatability under cyclic pressures varying from 38.45 to 177.82 Pa. To demonstrate its practical usage, we have successfully developed a 4 × 4 inductive pressure sensor array into a wearable keyboard for a smart electronic calendar application.
Highlights
Flexible sensing has attracted considerable attention in both academia and industries with a wide range of applications in smart wearable devices for human–machine interactions [1,2,3,4,5]
To demonstrate the potential utility in flexible electronics for our constructed utility in flexible electronics for our constructed and flexible inductive array, and flexible inductive pressure sensor array, we successfully developed thepressure sensor sensor into flexible we successfully developed the sensor into flexible electronic gadgets, i.e., a wearable smart calendar electronic gadgets, i.e., a wearable smart calendar touch board/keyboard
This paper reports a highly sensitive flexible pressure sensor array by utilizing the active units were recognized in the data processing and analysis
Summary
Flexible sensing has attracted considerable attention in both academia and industries with a wide range of applications in smart wearable devices for human–machine interactions [1,2,3,4,5]. Inductive sensors are widely used in the fields of displacement measurements, particle detections, and health monitoring because of their high resolution, long life time, good linearity, high stability, simple structure and immunity to environmental fluctuations [12,13,14,15,16]. According to the law of electromagnetic induction, an inductor can generate a magnetic field as current flows through it. The parameters, such as self-inductance coefficient, relative permeability and magnetic flux distribution, can be modified by external stimuli [14,15,16]. Kisic’s group has reported a method to detect seat occupancy by using an inductive-based wireless pressure sensor. Zhe’s group has reported an inductive sensor for detecting micro-scaled metallic debris in lubrication oil.
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