Self-shrinking soft demoulding for complex high-aspect-ratio microchannels

Abstract

Microchannels are the essential elements in animals, plants, and various artificial devices such as soft robotics, wearable sensors, and organs-on-a-chip. However, three-dimensional (3D) microchannels with complex geometry and a high aspect ratio remain challenging to generate by conventional methods such as soft lithography, template dissolution, and matrix swollen processes, although they are widespread in nature. Here, we propose a simple and solvent-free fabrication method capable of producing monolithic microchannels with complex 3D structures, long length, and small diameter. A soft template and a peeling-dominant template removal process are introduced to the demoulding process, which is referred to as soft demoulding here. In combination with thermal drawing technology, microchannels with a small diameter (10 µm), a high aspect ratio (6000, length-to-diameter), and intricate 3D geometries are generated. We demonstrate the vast applicability and significant impact of this technology in multiple scenarios, including soft robotics, wearable sensors, soft antennas, and artificial vessels.

Flow Casting Soft Shells with Geometrical Complexity and Multifunctionality

“…The dip‐coating method has been employed for both 1D hollow soft robotics and 3D hollow vascular replicas fabrication, [ 6,16,21 ] but the mold dissolution process is time‐consuming and may cause buckling in soft shells. [ 22 ] Whereas additive manufacturing could directly print 3D soft shells with high topological complexity for soft robotics, [ 4,23,24 ] it is hard to generate a smooth surface due to the layer‐by‐layer printing process and not a general approach for the scalability and mass production of soft hollow structures. Recently, bubble casting was developed to generate soft shells by blowing the liquid precursor through molds, which exhibit excellent design flexibility and fabrication scalability, [ 5 ] but only the planar geometries were presented.…”

“…Soft materials are extensively adopted in soft microfluidics [1,2] and soft robotics, [3][4][5][6] which have benefited and thrived in broad research in recent decades due to their high compliance and stretchability. [7,8] Studies in soft devices drastically increase in the last decades in various fields, particularly in human-machine interactions.…”

“…The dip-coating method has been employed for both 1D hollow soft robotics and 3D hollow vascular replicas fabrication, [6,16,21] but the mold dissolution process is time-consuming and may cause buckling in soft shells. [22] Whereas additive manufacturing could directly print 3D soft shells with high topological complexity for soft robotics, [4,23,24] it is hard to generate a smooth surface due to the Soft shells are ubiquitous in soft devices, e.g., soft robots, wearable sensors, and soft medial replicas. However, previous widely accepted methods, such as mold casting, dip coating, and additive manufacturing, are limited to thick shells due to the mold assembly and the large friction during demolding, long processing time for mold dissolution, and poor scalability, respectively.…”

Innervation of Sensing Microchannels for Three‐Dimensional Stimuli Perception

“…The structures can be easily fabricated by soft demolding proposed in our previous work. [ 3 ] According to the resistance change of the distributed sensing microchannels, both the tactile motions and force directions can be recognized. Finally, to present the sensing ability of internal stimuli, we fabricated a soft sensorized actuator containing orthogonally distributed actuating and sensing microchannels resembling muscle fiber and proprioceptors and demonstrated its proprioception for bending, elongation, and bending direction recognition.…”

Highly Integrated Multi‐Material Fibers for Soft Robotics

“…Multifunctional soft robots are particularly promising in tubular form to act as steerable endoscopes and catheters in minimally invasive procedures. [ 18 , 19 , 20 ] However, creating the soft multi‐material assemblies, which are necessary for dexterous movement and embedded functionality, [ 9 , 11 ] at relevant diameters (<3 mm) and lengths (>300 mm) is a feat that is highly challenging, for both conventional extrusion‐based techniques [ 21 , 22 , 23 ] and approaches adopted from macroscopic soft robotics relying on molding, [ 24 , 25 , 26 , 27 , 28 ] stereolithography, [ 29 ] 3D printing, [ 30 ] and manual processing. [ 31 ]…”