Printable and Stretchable Conductive Elastomers for Monitoring Dynamic Strain with High Fidelity

Abstract

Printable and stretchable conductive elastomers have promising applications for epidermal and wearable electronics, soft robotics, etc. However, these conductive materials usually present poor performances in monitoring dynamic strains. The monitored signals are distorted and lose key physical signs, which limit their practical applications. Through investigating kinetic behaviors of conductive pathways along longitudinal and transverse directions in these conductive materials, the physical mechanism of signal distortion under dynamic strains is interpreted. To overcome this strain sensing problem, an Ag‐Ecoflex‐polydimethylsiloxane (PDMS) elastomer by printing Ag‐filler‐Ecoflex‐matrix ink on PDMS is proposed. Compared to other conductive materials, the Ag‐Ecoflex‐PDMS elastomer has preferable dynamic performances, embodying smaller overshoot response, higher strain sensitivity, and lower hysteresis. A deep‐learning‐based dynamic calibration method is proposed to successfully correct the sensing signals and eliminate the hysteresis error to 0.1%. Moreover, the proposed Ag‐Ecoflex‐PDMS elastomers gain high electrical conductivities owing to thermal expansion and contraction of PDMS substrate during the thermosetting of conductive ink, and thus can be both excellent stretchable sensors and stretchable conductors. Demonstrations of monitoring knee motion with high fidelity and human–robot collaborative playing ping‐pong validate superior accuracy and robustness of the Ag‐Ecoflex‐PDMS elastomers for monitoring human dynamic activities, human‐machine collaboration, virtual reality, etc.

Low Hysteresis and Fatigue-Resistant Polyvinyl Alcohol/Activated Charcoal Hydrogel Strain Sensor for Long-Term Stable Plant Growth Monitoring

“…% PVA-AC was the highest, indicating that it has the best sensing performance ( Figure S3 ); therefore, we choose the 5 wt.% PVA-AC as the optimum ratio for our material. These results indicate that the mass ratio of the AC content has a significant effect on the mechanical properties of the hydrogel [ 32 , 33 ].…”

Screen-Printed Corrosion-Resistant and Long-Term Stable Stretchable Electronics Based on AgAu Microflake Conductors

“…Screen printing inks were developed based on the AgAu flakes, water-dispersed PU and green solvents, and printed stretchable conductors showed an initial conductivity of ≈3000 S cm –1 . Three-layer prints showed a dramatic increase in conductivity to ≈8500 S cm –1 , which is comparable to the best stretchable Ag flake conductors in the literature. ,, Printed conductors based on the AgAu flakes had good resistance to corrosion (H 2 O 2 solution) and tarnishing (SO 2 gas), while pure Ag-based conductors failed under the same conditions. To demonstrate the applicability of corrosion-resistant printed stretchable conductors, stretchable LED and NFC circuits were developed based on the AgAu conductors.…”

Technology Roadmap for Flexible Sensors

“…For example, although stretchable strain sensors using conductive elastomeric composites have been widely reported, their dynamic performance has rarely been investigated. Most studies only focus on quasi-static electric behavior, where the sensing performance was evaluated in a static state or in slow stretching–releasing processes (deformation speed <30 mm min –1 , strain rate <10% s –1 ) . Few studies have paid attention to the signal fidelity of strain sensors at higher deformation speeds, , which is more relevant to dynamic motions in real life, such as limb movements and hand gestures (speed >100 mm min –1 , strain rate >20% s –1 ) .…”