Covalent Bonding of Thermoplastics to Rubbers for Printable, Reel‐to‐Reel Processing in Soft Robotics and Microfluidics

Abstract

The lamination of mechanically stiff structures to elastic materials is prevalent in biological systems and popular in many emerging synthetic systems, such as soft robotics, microfluidics, stretchable electronics, and pop-up assemblies. The disparate mechanical and chemical properties of these materials have made it challenging to develop universal synthetic procedures capable of reliably adhering to these classes of materials together. Herein, a simple and scalable procedure is described that is capable of covalently laminating a variety of commodity ("off-the-shelf") thermoplastic sheets to silicone rubber films. When combined with laser printing, the nonbonding sites can be "printed" onto the thermoplastic sheets, enabling the direct fabrication of microfluidic systems for actuation and liquid handling applications. The versatility of this approach in generating thin, multifunctional laminates is demonstrated through the fabrication of milliscale soft actuators and grippers with hinged articulation and microfluidic channels with built-in optical filtering and pressure-dependent geometries. This method of fabrication offers several advantages, including technical simplicity, process scalability, design versatility, and material diversity. The concepts and strategies presented herein are broadly applicable to the soft robotics, microfluidics, and advanced and additive manufacturing communities where hybrid rubber/plastic structures are prevalent.

Soft Microreactors for the Deposition of Conductive Metallic Traces on Planar, Embossed, and Curved Surfaces

“…Further, by extending this deposition strategy to other functional inorganic materials, we could construct new variants of plastic/metal hybrid structures not easily accessible using other strategies. We believe that the methods and concepts presented herein (as represented by µ‐DECD) are unique in acheiving patterned depostion through confinement of the surface‐chemi‐cal processes within the microchannels without the need for sophisticated instruments, and are applicable to a variety of emerging technologies including: functional substrates for smart textiles, disposable healthcare monitoring systems, remotely controlled/powered soft robots (e.g., those that use polymeric films with metallic traces for communication or inductive coupling), antennas,[17a,b] and a range of low‐cost sensing electronics …”

Addressable, Stretchable Heating Silicone Sheets

“…Taylor, et al recently demonstrated a simple chemical platform that enables the bonding of many types of commercial polymers (with glass transition temperatures < 150°C) to pure silicone. [50] In Figure 6b,ii we also show that, due to both the elasticity of the silicone and the shape memory effect in the PLA variable stiffness sheet, [51,52] the material is able to recover some of the set shape when reheated after shape fixing. The ~90° bend flattened itself, recovering 69% of its bend, and the twisted 180° sample was able to recover 66% of its twist (see also Supplemental Video 4).…”

Microfluidics‐Based Biomaterials and Biodevices

“…Researchers describe a simple procedure to covalently bond commercial thermoplastic to silicone rubbers, in which (3‐ami‐nopropyl)triethoxysilane is used to aminate the surface of oxidized thermoplastics and oxidized by ultraviolet–ozone. Combining with laser printing, microfluidic devices can be directly fabricated in a low‐cost manner (Figure B) . This strategy demonstrates a new approach to the fabrication of microfluidic devices with advantages of process scalability and material diversity.…”

“…B) Laser printing of microfluidic devices by covalent bonding of thermoplastics to rubbers. Reproduced with permission . Copyright 2018, Wiley‐VCH.…”