Screen‐Printed, Low‐Cost, and Patterned Flexible Heater Based on Ag Fractal Dendrites for Human Wearable Application

Abstract

Achieving all‐printed, low‐cost, and large area electronic devices poses challenging requirements in employing printing technologies and conductive materials for flexible and wearable heaters. In this work, fully printed, scalable, and patterned flexible heaters based on Ag fractal dendrites (FDs) are fabricated through straightforward screen printing technology. The Ag FDs possess low sheet resistance with ≈0.83 Ω sq−1 when sintered at low temperature of 60 °C. The Ag FDs are directly printed on thin polyethylene terephthalate substrate to manufacture flexible heaters, exhibiting excellent heating performance with the saturation temperature up to ≈135 °C and rapid response time within 35 s under 4 V DC voltage. In addition, the Ag FDs heaters present lower power consumption (≈209.67 °C cm2 W−1), which is significantly better than traditional indium tin oxides (ITO) heaters (≈88 °C cm2 W−1). The sheet resistance of the devices remains stable after 2000 bending cycles with a radius of 10 mm, indicating that the outstanding mechanize stability of the heaters. Moreover, a large area (12 cm × 5 cm) heater with designable pattern is developed and attached to human body, indicating a bright future in next‐generation fully printed and wearable heating electronics application.

Multifunctional Ultrastretchable Printed Soft Electronic Devices for Wearable Applications

“…[9,35] Typically, the Ag FDs were dried at 60 °C for 12 h. At the same time, 0.125 g mL −1 SIS solution was formulated by dissolving SIS in xylenes via violent stirring for 4 h. Subsequently, the SIS solution, Ag FDs, and Disponer 904S were mixed together and ultrasonically stirred for 30 min to obtain the final homogeneous screen-printed Ag FDs conductive inks. [9,35] Typically, the Ag FDs were dried at 60 °C for 12 h. At the same time, 0.125 g mL −1 SIS solution was formulated by dissolving SIS in xylenes via violent stirring for 4 h. Subsequently, the SIS solution, Ag FDs, and Disponer 904S were mixed together and ultrasonically stirred for 30 min to obtain the final homogeneous screen-printed Ag FDs conductive inks.…”

“…[18,21,22] However, many researchers focused on how to fabricate the individual electronic device with improving electrical properties, sensing sensitivity, and heating performance. [9,23] Recently, www.advelectronicmat.de structure mainly consisting of functional conductive layer, and substrate layer, which can be prepared by depositing conductive materials on the surface of the substrate or embedding it in the substrate. [2,4,22,35] The preparation methods mainly include coating (spin coating, spray coating, dip coating, etc.…”

“…[39,40] Among these methods, screen-printing method is a more mature industrial technology with easy operation, low cost, and mass production capability, which can be rapidly patterned. [9,35,41] In our previous work, the wearable strain sensor with excellent sensing performance was prepared by screenprinting method, but its mechanical stability was poor due to low adhesion of the conductive functional layer to the substrate. [35] Moreover, the commonly used stretchable polymer substrates (polydimethylsiloxane [PDMS], Ecoflex) have a low surface energy, thus the conductive ink cannot be directly deposited onto the surface of the polymer substrate by screenprinting.…”

“…Compared with the carbon-based materials (such as graphene, [30] CNTs, [5] and carbonized fibers [31] ), the metallic nanomaterials, especially of silver nanomaterials (including Ag nanowires, Ag flakes) usually have superior electrical conductivity. [9,28,35] In our previous works, the preparation process of the Ag FDs is simple and fast, enabling mass production. The unique structure of Ag FDs provides larger surface area, which is beneficial to maintain the connection of conductive path under tensile strain.…”

“…[32][33][34] Among in silver nanomaterials, silver fractal dendrites (Ag FDs) with unique branch structure could obtain high conductivity at lower sintering temperature (<80 °C). [9,28] Therefore, the Ag FDs is an ideal conductive material for fabricating the MWEs with high conductivity, excellent sensing performance and Joule heating performance.Another challenge is to exploit a simple and fast way to fabricate the high-performance MWEs. [9,28,35] In our previous works, the preparation process of the Ag FDs is simple and fast, enabling mass production.…”