Enhancement of Pressure‐Sensitive Adhesive by CO₂ Laser Treatment

Abstract

Pressure-sensitive adhesives (PSAs) are polymeric films that form noncovalent bonds to surfaces when pressed against a substrate. They are widely used for domestic purposes, industrial packaging, the medical industry, aerospace, and research. [1][2][3][4][5] This group of adhesives is well known for its convenience and affordable price. PSAs can be stuck to different surfaces without additional processing and detached without leaving residue. [3,6] One particularly popular PSA is "Very High Bond" (VHB, by 3M) because its elastic properties make it suitable for various soft and stretchable devices. For example, it has been used for wearable and microfluidic devices, including stretchable sensors and actuators in soft and medical robotics. [7][8][9][10][11][12][13][14] PSAs adhere to surfaces because of van der Waals (VdW) forces. Viscoelastic dissipation near the interface further enhances adhesion. [1,6,15] Chemical composition is essential because it defines VdW forces and surface energy and because it affects viscoelasticity. [1,6,15] The adhesion force of PSAs is determined by peel strength, shear strength, and tackiness. The latter relates to the ability of the PSA to wet the contact substrate. [2,3] Researchers often seek to enhance the adhesion between a PSA and a substrate [5] to increase the durability of a device. [7] In addition, researchers are looking for precise adhesion control [4] and an approach to achieve the required peeling, shear, and tack properties of PSAs. [3] The chemical composition of acrylic PSAs and their surface can be modified with oxygen or nitrogen plasma and oligomers or aluminum nitride particles. [16][17][18][19][20] These approaches provide a way to enhance the adhesion with additional materials and processing steps but require specialized and well-equipped technical facilities. Here, a simple way to modify adhesion without additives is reported, which is compatible with rapid prototyping.The proposed approach is based on a serendipitous discovery: treating VHB tape with a common CO 2 laser "cutter" can improve the adhesion. [7] Here, the proposed treatment method shows an improvement in adhesion by modifying the viscoelasticity of the surface layer without modifying the bulk material. Whereas most prior studies primarily test PSA adhesion on metals, the proposed surface treatment method is characterized on different substrates such as organic materials, inorganic materials, metal,

A Variable Stiffness Magnetic Catheter Made of a Conductive Phase‐Change Polymer for Minimally Invasive Surgery

“…The SCF is given by the relation where K r and K s are the bending stiffnesses of the VST in the rigid and soft states, respectively. [ 55,56 ] The effective bending stiffness of the thread, K , is defined by the relation where E avg is the Young's modulus of the entire device. I i is the moment of inertia (second moment of area) of different layers from i equal to 0 to N .…”

Bioinspired Structures for Soft Actuators

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