Fabrication and characterization of self-folding thermoplastic sheets using unbalanced thermal shrinkage

Abstract

Self-folding or micro-origami technologies are actively investigated as a novel manufacturing process to fabricate three-dimensional macro/micro-structures. In this paper, we present a simple process to produce a self-folding structure with a biaxially oriented polystyrene sheet (BOPS) or Shrinky Dinks. A BOPS sheet is known to shrink to one-third of its original size in plane, when it is heated above 160 °C. A grid pattern is engraved on one side of the BOPS film with a laser engraver to decrease the thermal shrinkage of the engraved side. The thermal shrinkage of the non-engraved side remains the same and this unbalanced thermal shrinkage causes folding of the structure as the structure shrinks at high temperature. We investigated the self-folding mechanism and characterized how the grid geometry, the grid size, and the power of the laser engraver affect the bending curvature. The developed fabrication process to locally modulate thermomechanical properties of the material by engraving the grid pattern and the demonstrated design methodology to harness the unbalanced thermal shrinkage can be applied to develop complicated self-folding macro/micro structures.

Untethered microgripper-the dexterous hand at microscale

“…For microgrippers actuated by thermo, there are currently two main driving mechanisms. The first one is to utilize the temperature-sensitive deformation of materials (Danielson et al 2017;Schmidt and Eberl 2001). This type of microgripper contains several hinges and is actuated by the residual stress generated in the fabrication process.…”

Photolithographically Patterned Hydrogels with Programmed Deformations

“…are severallithographic strategies using X-ray,gamma-ray,electron beam,a nd photo [57][58][59][60][61][62][63] to trigger the formation or modification of an etwork at programmed regions.T he photo-initiated polymerization and crosslinking is mostc ommonly used to preparep atterned hydrogels, because (i)light is ac lean energy to trigger the reaction of monomer,o ligomer,o rp olymer,( ii) light is relatively cheap and safe, when compared to X-ray and gamma-ray,( iii)the reaction can be facilely controlled at specific regions with spatial precisionw hen guided by ap hoto mask, (iv) the methodc an generate large-area gel patterns with high fidelity and various features, and (v) multiple step patterning can be realized thanks to the open network of gel, which enables precursor solutiont od iffuse in for subsequent photo-triggered reactiona nd unreacted reagents to be removed.T his methodc an produce hydrogels with desirable size and features at specific regions or control the distribution of one component in another gel matrix. [64][65][66][67][68] Patterned hydrogels have numerousa pplicationso wing to the rich functionalities of patterned polymers and aw ide range of applicationso ft he patterns.…”

Preparation of a high‐performance thermally shrinkable polystyrene SERS substrate via Au@Ag nanorods self‐assembled to detect pesticide residues

“…This creates a shape‐memory effect in the processed plastic, which gives stretched polystyrene molecules more leeway when they are heated and softened again, and they tend to return to their more twisted, shrunken state before stretching. The film, stretched in both directions, contracts more evenly, so that after some magical distortions, the film eventually returns to a nearly flat state, without any visible distortion of the pattern . In 2008, Chen et al used Shrinky Dinks to create tiny structures for microfluidics applications in fields like stem cell research .…”

“…The film, stretched in both directions, contracts more evenly, so that after some magical distortions, the film eventually returns to a nearly flat state, without any visible distortion of the pattern. [28][29][30][31] In 2008, Chen et al used Shrinky Dinks to create tiny structures for microfluidics applications in fields like stem cell research. [32] TSP has since been used in both microfluidic and micro/nanodevice manufacturing.…”