Stretchable, Washable, and Rewritable Electrophoretic Displays with Tough Hydrogel–Elastomer Interface

Abstract

Typically, up-to-date displays for wearable applications require three key features: (1) long-term reliability under cycling deformation, [13] (2) biocompatibility and stretchability while adhering to the human body, [14] and (3) low power consumption. [15] For instance, Koo et al. demonstrated a deformable electrochromic skin with high durability under repeated compressive force (with a bending radius of 8 mm, 10 000 cycles) and tensile strains (approximately 100% up to 15 000 s). [16] For biocompatibility, Huang et al. developed a flexible transient device based on transparent fish gelatin films that are naturally degradable to eliminate environmental pollution. [17] To address the power consumption, Li et al. reported a novel yet simple implementation of a high-definition resolution E-ink device with a low operation voltage of 1 V by synthesizing Melanin E-Ink. [18] In the commercial industry, E-Ink Inc. developed mass-product technological revolutions with electrophoretic electrical ink microcapsule encapsulation and doctor blade coating imprinting manufacturing. [19][20][21] All of the efforts in academia and industry have simultaneously accelerated the exploration of bistable electrophoretic displays, which are reflective displays. However, owing to the deformable hierarchical structure or the emergence of small bubbles under long-term and repeatable deformation, most devices suffer from insufficient reliability and optical parameter decrement under large deformation, which limits their integration into practical applications. Therefore, more robust device structures are imperative for efficient wearable displays.Hydrogels and elastomer hybrids produced by in situ adhesion decoration are strong structures with the advantages of biocompatibility, stretchability, and tough adhesion, which have been demonstrated for wearable triboelectric nanogenerators, [22] skin electronics, [23] 3D printing, [24] hydrogel paint, [25] and stretchable electroluminescent skin. [26] For instance, Zhao et al. demonstrated that robust hydrogel-solid interfaces are particularly critical to the functionality and reliability of stretchable hydrogel-based electronic devices. [27] To our knowledge, without bonding, the delamination structure of hydrogel-elastomer devices has an inherent defect: low adhesion energy between the hydrogels and elastomers (typically below 1 J m −2 ). [28] The defect may result in small bubbles that are likely to emerge and cause failures, such as detachment. [29] Moreover, small bubbles Tremendous advances in stretchable and biocompatible electronics have led to broad requirements of wearable display devices. However, most devices suffer from insufficient reliability owing to structural mismatch and bubbles under repeated deformation. To address this issue, this article presents a stretchable electrophoretic display (SEPD) with reinforced adhesion by in situ adhesion decoration between the hydrogel electrode and the elastomer display layer. The SEPD with a maximum strain of over 80% can still operate prope...

Textile-based electrophoretic electronic paper displays with machine-washable, tailorable, and thermostatic functions for truly wearable displays

“…In other words, the proposed EPD encapsulated by the WPU will obtain a higher contrast ratio in the same driving voltage. Compared to the optimal contrast ratio of 2.61 under 200 V with PDMS encapsulation in previous research, 16 the following data of contrast ratio of 13 under 30 V (Fig. 3e) has evidenced the choice of the WPU elastomer as the matrix material to encapsulate microcapsules is available.…”

Conductive polymer based hydrogels and their application in wearable sensors: a review

“…The casting and molding process is a conventional approach to create CPHs with desirable morphology with advantages such as simplicity, high throughput and low cost. [104][105][106][107] In this method, a hydrogel pre-solution is poured into a shaped mold, followed by polymerization which can be triggered by a range of stimulus, i.e. light, chemicals, or heat for gelling.…”

An electrophoretic e‐paper device with stretchable, washable, and rewritable functions

“…In general, interfacial bonding issues can be tackled in two ways, including surface treatment and adopting adhesive 18–20 . Recently, our group has realized strong bonding between tough elastomer and transparent hydrogel via benzophenone decoration and ultraviolet (UV)‐initiated polymerization 17 . Daniela et al have applied the cyanoacrylate‐based adhesives dispersion to form tough and instant bonds between separate hydrogels, hydrogels/elastomers, and hydrogels/solid.…”

“…[18][19][20] Recently, our group has realized strong bonding between tough elastomer and transparent hydrogel via benzophenone decoration and ultraviolet (UV)-initiated polymerization. 17 Daniela et al have applied the cyanoacrylate-based adhesives dispersion to form tough and instant bonds between separate hydrogels, hydrogels/elastomers, and hydrogels/solid. However, the above methods require additional curing processes or are not biofriendly to creatures.…”

“…During the past decade, the commercial applications of EPD have evolved in a variety of directions 13–16 . Recently, the EPD with stretchable property has been demonstrated to be a powerful candidate as a wearable display device 17 . However, overcoming the low interfacial toughness with the conventional sandwich structure is still challenging to enhance the stretchability and uniformity simultaneously, primarily under the long‐term cycling deformation.…”