Study and tailoring of screen-printed resistive films for disposable strain gauges

The present work aims at fabrication and characterization of the novel dispersion based piezoresistive strain gauges. The novelty of present work is in the material-set and technique used to synthesize the low-cost, graphite powder based composites of various proportions without the need for additional pretreatment or functionalization. When filler and resins are properly formulated, they can be printed in variety of shapes over different substrates such as glass, acrylic, plastics (such as PVC, PDMS, PMMA, PET, PI), metal foils, paper etc. They may be of great interest to integrate mechanical, chemical or temperature sensing functions in many electronic circuits and devices. In the current work, the resistive composite dispersions are screen-printed on glass substrate to fabricate the strain gauges and to study their piezoresistive strain performance. Graphite particles in the powder are found to have irregular shape and size. Thickness of screen-printed films varies in the range 13-27 mu m. Gauge factors ranging from 17 up to 70 is achieved for the strain gauges having satisfactory stability, linearity and repeatability. The variation in GF is found to be less than 2%. Maximum hysteresis and nonlinearity were observed to be less than 2% FSO (Full Scale Output). Repeatability is found to be minimum 98%. The dispersion composition is tuned to obtain a better sensitivity. Regarding temperature effects, all the strain gauge samples exhibited a negative value of TCR, lowest being -2 x 10(-4)/degrees C. Graphite powder and printing ink are inexpensive and commercially-available. Also, technique used to fabricate strain gauges avoids high-end equipment and expensive clean room facilities. These devices are robust, easy to scale & pattern, safely disposable strain gauges with are fairly good performance fabricated at low cost. These features make them a good candidate for pressure sensors, weigh bridges, displacement sensors, crack sensors, strain sensors etc. The real time potential applications are in different sectors such as automotive, aerospace, biomedical, oceanography and industrial purposes. (C) 2019 Elsevier B.V. All rights reserved.