We demonstrate a flexible strain-gauge sensor and its use in a wearable application for heart rate detection. This polymer-based strain-gauge sensor was fabricated using a double-sided fabrication method with polymer and metal, i.e., polyimide and nickel-chrome. The fabrication process for this strain-gauge sensor is compatible with the conventional flexible printed circuit board (FPCB) processes facilitating its commercialization. The fabricated sensor showed a linear relation for an applied normal force of more than 930 kPa, with a minimum detectable force of 6.25Pa. This sensor can also linearly detect a bending radius from 5mm to 100mm. It is a thin, flexible, compact, and inexpensive (for mass production) heart rate detection sensor that is highly sensitive compared to the established optical photoplethysmography (PPG) sensors. It can detect not only the timing of heart pulsation, but also the amplitude or shape of the pulse signal. The proposed strain-gauge sensor can be applicable to various applications for smart devices requiring heartbeat detection.
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http://dx.doi.org/10.1016/j.bios.2017.03.016 | DOI Listing |
Sensors (Basel)
November 2024
Department of Civil, Construction, and Environmental Engineering, Iowa State University, Ames, IA 50011, USA.
This paper explores the development of 3D-printed self-sensing Ultra-High Performance Concrete (UHPC) by incorporating graphite (G) powder, milled carbon microfiber (MCMF), and chopped carbon microfiber (CCMF) as additives into the UHPC matrix to enhance piezoresistive properties while maintaining workability for 3D printing. Percolation curves were established to identify optimal filler inclusion levels, and a series of compressive tests, including quasi-static cyclic, dynamic cyclic, and monotonic compressive loading, were conducted to evaluate the piezoresistive and mechanical performance of 29 different mix designs. It was found that incorporating G powder improved the conductivity of the UHPC but decreased compressive strength for both mold-cast and 3D-printed specimens.
View Article and Find Full Text PDFACS Appl Mater Interfaces
December 2024
Key Laboratory of MEMS of the Ministry of Education, Southeast University, Nanjing 210096, China.
Mechanically robust and electrically conductive hydrogels hold significant promise for flexible device applications. However, conventional fabrication methods such as casting or injection molding meet challenges in delivering hydrogel objects with complex geometric structures and multicustomized functionalities. Herein, a 3D printable hydrogel with excellent mechanical properties and electrical conductivity is implemented via a facile one-step preparation strategy.
View Article and Find Full Text PDFInt J Biol Macromol
December 2024
Guangxi Key Laboratory of Petrochemical Resource Processing and Process Intensification Technology, School of Chemistry and Chemical Engineering, Guangxi University, No. 100, Daxuedong Road, Xixiangtang District, Nanning 530004, China. Electronic address:
Stretchable bioelectronics advancements have placed higher demands on conductive elastic film. However, the high conductivity of elastomers largely relies on the substantial content of costly conductive fillers while being environmentally unfriendly. Herein, in order to achieve a win-win situation for the economy and the environment, guar hydroxypropyltrimonium chloride (CGG) was introduced in epoxy natural rubber (ENR) to prepare biobased conductive film.
View Article and Find Full Text PDFSensors (Basel)
October 2024
Ground Technology Research Institute, Agency for Defense Development, Daejeon 34186, Republic of Korea.
This paper presents an innovative piezo-actuated fast-steering mirror (FSM) that integrates control design and system operation to improve the tracking performance of laser beam steering (LBS) systems. The proposed piezoelectric FSM is centered on two pairs of stacked actuators functioning in the tip-tilt direction via novel flexible hinges with strain-gauge sensors for position measurement. The suggested flexible hinge scheme allows the first fundamental resonance mode with the optical mirror to exceed 400 Hz while achieving an actuation range of ±5 mrad.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
November 2024
Department of Mechanical Engineering, Vanderbilt University, Nashville, TN 37212.
Continuously monitoring human airway conditions is crucial for timely interventions, especially when airway stents are implanted to alleviate central airway obstruction in lung cancer and other diseases. Mucus conditions, in particular, are important biomarkers for indicating inflammation and stent patency but remain challenging to monitor. Current methods, reliant on computational tomography imaging and bronchoscope inspection, pose risks due to radiation and lack the ability to provide continuous real-time feedback outside of hospitals.
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