Sustainable manufacturing of sensors onto soft systems using self-coagulating conductive Pickering emulsions

Abstract

Compliant sensors based on composite materials are necessary components for geometrically complex systems such as wearable devices or soft robots. Composite materials consisting of polymer matrices and conductive fillers have facilitated the manufacture of compliant sensors due to their potential to be scaled in printing processes. Printing composite materials generally entails the use of solvents, such as toluene or cyclohexane, to dissolve the polymer resin and thin down the material to a printable viscosity. However, such solvents cause swelling and decomposition of most polymer substrates, limiting the utility of the composite materials. Moreover, many such conventional solvents are toxic or otherwise present health hazards. Here, sustainable manufacturing of sensors is reported, which uses an ethanol-based Pickering emulsion that spontaneously coagulates and forms a conductive composite. The Pickering emulsion consists of emulsified polymer precursors stabilized by conductive nanoparticles in an ethanol carrier. Upon evaporation of the ethanol, the precursors are released, which then coalesce amid nanoparticle networks and spontaneously polymerize in contact with the atmospheric moisture. We printed the self-coagulating conductive Pickering emulsion onto a variety of soft polymeric systems, including all-soft actuators and conventional textiles, to sensitize these systems. The resulting compliant sensors exhibit high strain sensitivity with negligible hysteresis, making them suitable for wearable and robotic applications.

Cutaneous Ionogel Mechanoreceptors for Soft Machines, Physiological Sensing, and Amputee Prostheses

“…Designing touch‐sensitive skins to mimic various functions and properties of natural epidermal tissue is an essential but open challenge in the fields of wearable electronics [ 1–6 ] and robotics. [ 7–12 ] Over the past decades, a number of artificial skins have been developed based on various materials—from rigid to soft electronic components [ 13,14 ] —and mechanisms, such as capacitive, [ 3,15,16 ] piezoresistive, [ 17,18 ] piezoelectric, [ 19,20 ] triboelectric [ 21,22 ] pressure sensors.…”

Transparent Soft Actuators/Sensors and Camouflage Skins for Imperceptible Soft Robotics

“…Ethanol-based conductive composite rather than conventional solvents such as toluene or cyclohexane could prevent decomposition of the prefabricated actuator (Figure 9c). [136] This introduces new approach not by simply combining each components but by integrating in the fabrication step.…”

An Anti‐Freezing, Ambient‐Stable and Highly Stretchable Ionic Skin with Strong Surface Adhesion for Wearable Sensing and Soft Robotics

“…[11] Noticeably, because of the inherent material match and functional complementarity between artificial skins and soft robots, there have been significant research efforts spent on developing skin-like stretchable and wearable sensors for integration with various soft robotic systems. [12][13][14][15][16][17] This rapd development would enable soft robots to interact with their users and environments more intelligently. Among different types of sensing materials used in artificial skins, hydrated and ionic materials such as deformable and tough ionic hydrogels are one of the most suitable sensor candidates to mimic the multiple functions of biological systems.…”