A Flexible Patch-Type Strain Sensor Based on Polyaniline for Continuous Monitoring of Pulse Waves

Abstract

A flexible, patch-type strain sensor is described for continuous monitoring of pulse waves. The proposed sensor exploits the piezo-resistivity of the conductive polymer, polyaniline (PANI), to detect dynamic volume changes in blood vessels owing to pulse waves. The proposed PANI film was fabricated through electrodeposition, which is considered as a suitable low-cost technique for mass production in the sensor manufacturing industry. Thus, it is prospective for a disposable wearable sensing system solution in remote healthcare applications. Besides, a flexible sensor packaging can be achieved by laminating the PANI films and an ECOFLEX elastomer to the film bandage. The proposed PANI sensor has high sensitivity (gauge factor of 74.28) and linearity (R 2 = 0.99). It also showed a high correlation with commercially available photoplethysmography (PPG) sensor with the small bias and confidence interval to the PPG sensor: bias < 0.1% and confidence interval < 3% for all subjects. Moreover, the proposed PANI sensor was tested for prospective circulatory system-related applications such as measuring heart rate, stiffness index, and pulse transit time. Finally, the proposed study suggests that the proposed PANI sensor is a promising candidate for continuous, long-term, unobtrusive pulse wave monitoring, which can provide real-time insights into an individual's health status.

Recent Progress in Conducting Polymer Composite/Nanofiber-Based Strain and Pressure Sensors

“…Interestingly, dopant solution concentration effectively alters the wrinkling patterns and the wavelength of the patterns. The additional factor of thickness with its relation to sensitivity and linearity was clearly highlighted [121].…”

A smart functional surfactant activated conductive polymer coated on paper with ultra-sensitive humidity sensing characteristics

“…However, the synthesized PANI can be further explored by stacking the multiple layers of the sensor, which could spontaneously form microstructure air gaps between the layers, forming a conductive network between the layers. Since we have explored PANI/SLS for humidity sensing performance using a single layer of the sensor, we restricted the investigation to a single sensor layer for pressure sensing [75][76][77]. The poor sensitivity of the sensor against different pressure conditions suggests excellent selectivity of the sensor for humidity sensing.…”

“…Since we have explored PANI/SLS for humidity sensing performance using a single layer of the sensor, we restricted the investigation to a single sensor layer for pressure sensing. [75][76][77] The poor sensitivity of the sensor against different pressure conditions suggests excellent selectivity of the sensor for humidity sensing. High sensitivity, selectivity, repeatability, lightweight, ease of fabrication, improved electrical properties and quick response along with low hysteresis could make the PANI/SLS coated paper sensor a potential material for humidity sensing application.…”

Frequency Characteristics of Pulse Wave Sensor Using MEMS Piezoresistive Cantilever Element

“…Even though the effects of skin tone and pigmentation are non-negligible [ 13 , 14 ], optical sensors are suitable for miniaturization because of their simple components; hence, they have been used in commercial smartwatches and pulse oximeters. By contrast, mechanical sensors measure pulse waves by detecting pulse-induced skin deformation above the blood vessel, which typically involves strain or pressure [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ]. Mechanical detection provides direct information regarding physical phenomena occurring in the blood vessels.…”

“…Mechanical detection provides direct information regarding physical phenomena occurring in the blood vessels. Strain sensors are typically fabricated using flexible polymers and can be attached to the skin directly [ 15 , 16 , 17 , 18 ]. Meanwhile, pressure sensors utilize silicon-based sensor components with high functionalities.…”