Component assembly with shape memory polymer fastener for microrobots

Abstract

Adhesives are generally used for the assembly of microrobots, whereas bolts, screws, or rivets are used for larger robots. Although adhesives are easy to apply, lightweight, and small, they cannot be used for repeated assembly and disassembly of parts. In this paper, we present a novel microfastener composed of a polyurethane-based shape memory polymer (SMP) that is lightweight and small but that is easily detached for disassembly. This was achieved by using the shape recovery and modulus change of the SMP. A sheet of macromolded SMP was laser machined into an I-beam-shaped rivet, and notches were added to the structure to prevent stress concentration. Pull-off tests showed that, as the notch radius increased, the disengagement strength of the rivet fastener decreased and the reusability increased. Through the elastoplastic model, a single SMP rivet was calculated to have maximum disengagement strength of 150 N cm−2 in the elastic range, depending on the notch radius. The fasteners were applied to a jumping microrobot. The legs and body were assembled with ten fasteners, which showed no permanent deformation after impact during jumping movements. The legs were easily replaced with ones of different stiffness by heating the engaged sites to make the fasteners compliant and detachable. The proposed detachable SMP microfasteners are particularly useful for testing the isolated performance of microrobot components to determine the optimal designs for these components.

Enhanced shape memory performance of polyurethanes via the incorporation of organic or inorganic networks

“…Four approaches have been set forth to overcome poor recovery ratio and mechanical properties of PUs by developing either chemical or physical modications: (1) adjusting the hard-to-so segment ratio, [4][5][6][7] (2) enhancing the strength and number of ionic forces or hydrogen bonding, 8,9 (3) incorporating crosslinking networks, 10,11 and (4) blending with inorganic materials or creating organic/inorganic hybrids. [19][20][21][22] In order to enhance the shape memory performance, the PUs with different kinds of organic segments or inorganic units based crosslinking networks have been developed (Fig. [14][15][16][17][18] Because of the ability of SMPs to perform complex movements on demand, many researchers are also pursuing high-tech applications including aerospace, active disassembly, adhesive systems, and energy storage, and so on.…”

Role of compliant leg in the flea-inspired jumping mechanism

“…Fig. 3 (a) The Flea-inspired jumping mechanism assembled with SMP rivet fasteners [15]. The leg in this figure is sample no.…”

“…To easily switch the legs and minimize damage, shape memory polymer (SMP) rivet fasteners [15] are employed, as shown in Fig. 3 (a).…”

“…3 (b). With these properties, SMP rivet fasteners can be reversibly used and can achieve a high disengagement force of up to 7 N [15] while weighing only 0.003 g each. The SMP rivet fastener is designed as a simple I-beam shape and is installed through a hole inside the four-bar transmission mechanism, as shown in Fig.…”

Photoresponsive Soft‐Robotic Platform: Biomimetic Fabrication and Remote Actuation

“…

wileyonlinelibrary.com

nanorods, [ 6,7 ] carbon nanotubes (CNTs), [ 8,9 ] graphene, [ 10,11 ] etc. Accompany with the development of stimulus-responsive materials, various types of external stimulus, including electric, [ 12,13 ] heat, [14][15][16] light, [ 17,18 ] magnetic, [19][20][21] chemical stimulus, [ 22 ] pneumatic stimulus, [ 23 ] and so forth, have been successfully employed to develop biomimetic or bio-inspired microrobotic systems applying in microjets, [ 16 ] microgrippers, [ 24,25 ] drilling of tissues, [ 26 ] drug and cell delivery, [ 27,28 ] fi xing cancer cells, [ 29 ] artifi cial muscles, [ 30 ] and some other smart microstructures.Because of their ability in wireless/ remote control, low noise, localized driven ability rather than whole-fi eld driven, [ 31 ] light-driven microrobots have attracted more and more attention in novel microbio-robots or micro-motors for biological use. Accompany with the development of stimulus-responsive materials, various types of external stimulus, including electric, [ 12,13 ] heat, [14][15][16] light, [ 17,18 ] magnetic, [19][20][21] chemical stimulus, [ 22 ] pneumatic stimulus, [ 23 ] and so forth, have been successfully employed to develop biomimetic or bio-inspired mi...

…”