Bioinspired Adhesive Architectures: From Skin Patch to Integrated Bioelectronics

Abstract

on dry and rough surfaces (maximum ≈10 N cm −2 ). [1] Close observations have indicated nanoscale hairs of high aspect ratio (AR) with slated tips. [21][22][23][24][25][26][27][28][29][30] This geometry allows directional appliance of van der Waals forces against engaged surfaces for stable attachment. The attachment strategies and fixation systems of beetles have also been investigated. [9] Concave, mushroom-shaped architectures on the forelegs of beetles ensure stable adherences onto rough, waxy surfaces [31][32][33][34][35][36] or locomotion via capillary adhesion. [37][38][39] Studies on their attachment systems revealed that the mushroom-shaped structures with wide concave tips can generate van der Waals interactions [40] as well as a suction effect against engaged surfaces. [41,42] Moreover, needles located in the proboscis of mosquitos [43][44][45][46] or endoparasites (e.g., Pomphorhynchus laevis) [47] alike, induce mechanical interlocking on dry skin or wet organs. The needles provide strong adhesion in both normal and shear directions for the insect species to easily consume nutrients. Recently, the architectures of octopus suckers were investigated to understand their underlying attachment mechanism. Existing in clusters on octopus tentacles, suction cups are crucial for octopi's survival underwater for functions such as preying, grasping, locomotion, and even sensing. The cup-shaped protruding chamber (infundibulum) is known to adapt and seal conformably on rough surfaces. [12,13,15,48] Meanwhile, the dome-like protuberance in the lower chamber (acetabulum) forms pressure difference between the segregated lower and upper chambers within the suction cup architecture. [49] This enhances suction stress to adhere strongly onto wet or underwater surfaces. The footpads of slugs are covered with structures of microscale compression waves with viscous mucus. This can be used to both lubricate a slug's movement over surfaces and facilitate the transfer of adhesive force to the engaged surfaces. [16,19,20,[50][51][52] Specifically, the mucus with interpenetrating positively charged chemistries produce pedal waves; this in all creates an adhesive and elastic dissipative matrix, and guides the movement of slugs on attached surfaces. [53] Hence, structural features within the as-mentioned organisms have built the platform of bioinspired adhesive systems for potential use in clean transfer systems, [54][55][56][57][58][59] soft robotics, [60,61] stimuli-responsive adhesives for dry or wet surfaces, [62][63][64] and various wearable devices with diagnostic and therapeutic functionalities. [65][66][67][68][69] Among various applications of bioinspired multiscale architectures, patches attachable to skin have been of high interest (Figure 1b). Human skin, the outermost organ of the human The attachment phenomena of various hierarchical architectures found in nature have extensively drawn attention for developing highly biocompatible adhesive on skin or wet inner organs without any chemical glue. Structural adhesive sy...

Nanofiber‐Reinforced Silver Nanowires Network as a Robust, Ultrathin, and Conformable Epidermal Electrode for Ambulatory Monitoring of Physiological Signals

“…Measurement of Adhesion Force : The adhesion force on skin was measured by previously reported methods . The force was measured by a digital force meter (Mark‐10, USA).…”

“…The high conformability of the NEE is likely attributed to the van der Waals force that becomes dominant, as the NEE is extremely soft and thin . The adhesion of the NEE to the human skin in both pulling and peeling direction was measured by using procedures reported previously . The adhesion strength of the pulling‐off and the peeling‐off is ≈0.32 and ≈0.20 N cm −2 , respectively (Figure S9, Supporting Information).…”

Skin‐Friendly Electronics for Acquiring Human Physiological Signatures

“…[42] Therefore, the loading quantity could be calculated via dividing the total doping amount by substrate size. [9] The postmortem pigskins for adhesion tests were obtained from a local market and stored frozen, as following well-established protocols. Finally, copper wires were attached to the pin position using silver paste.…”

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exercise that may last for hours or even days. [8,9] However, just like many skin adhesives and transdermal patches, the strong adhesive design in many skin-mounted devices usually results in difficult detachment after their use, causing skin irritation, pain and even secondary damage to the wound when used, for example, as a wound healing dressing. [8,9] However, just like many skin adhesives and transdermal patches, the strong adhesive design in many skin-mounted devices usually results in difficult detachment after their use, causing skin irritation, pain and even secondary damage to the wound when used, for example, as a wound healing dressing.

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Biomimetic Meta‐Structured Electro‐Microfluidics

“…The final MSMs constitute with integrated ordered micro-and nanostructures and exhibit spontaneous liquid transfer, fluorescence enhancement, and intimate skin contact. [15] These ordered column arrays are common used in microfluidic chips, capacitive electrodes, and superadhesive materials. They can be used as chip-on-skin sensors for biochemical-physiological hybrid monitoring sensing of the human body and as organ chips for cell culture and metabolite analysis under drug treatment.…”