Autonomous planning and control of soft untethered grippers in unstructured environments

Abstract

The use of small, maneuverable, untethered and reconfigurable robots could provide numerous advantages in various micromanipulation tasks. Examples include microassembly, pick-and-place of fragile micro-objects for lab-on-a-chip applications, assisted hatching for in-vitro fertilization and minimally invasive surgery. This study assesses the potential of soft untethered magnetic grippers as alternatives or complements to conventional tethered or rigid micromanipulators. We demonstrate closed-loop control of untethered grippers and automated pick-and-place of biological material on porcine tissue in an unstructured environment. We also demonstrate the ability of the soft grippers to recognize and sort non-biological micro-scale objects. The fully autonomous nature of the experiments is made possible by the integration of planning and decision-making algorithms, as well as by closed-loop temperature and electromagnetic motion control. The grippers are capable of completing pick-and-place tasks of biological material at an average velocity of 1.8 ±0.71 mm/s and a drop-off error of 0.62 ±0.22 mm. Color-sensitive sorting of three micro-scale objects is completed at a velocity of 1.21 ±0.68 mm/s and a drop-off error of 0.85 ±0.41 mm. Our findings suggest that improved autonomous untethered grippers could augment the capabilities of current soft-robotic instruments especially in advancedtasks involving manipulation.

Soft Robotic Grippers

“…When developing stimuli‐responsive polymers and gels, researchers often demonstrate soft grippers as a potential application. Such materials have shown grasping in response to the application of various external stimuli including chemical (pH change, salt concentration, and solvent exposure), dissolution, humidity change, electrical, thermal, optical, and magnetic . Those stimuli triggered actuators exploit swelling, ion migration, oxidation, thermal expansion, phase transition, and field deformations.…”

“…A promising application of such stimuli‐responsive materials are microgrippers for assembly of micro‐objects, surgery, and drug delivery . Figure a top shows schematics of a microgripper developed by Ongaro et al, consisting of folding arms that can be actuated by thermal stimulus on a hydrogel ( N ‐isopropylacrylamide‐ co ‐acrylic acid) integrated with a stiff frame (SU‐8 polymer). The gripper has diameters of 4 and 0.8 mm in the flat and folded states, respectively.…”

“…a) Thermally‐responsive hydrogel. Reproduced with permission . Copyright 2016, The Authors, published by Springer Nature.…”

Shapeable Material Technologies for 3D Self‐Assembly of Mesoscale Electronics

“…With the help of compatible lithographic techniques and, more importantly, development of novel lithographically processable strain‐engineering materials and composites, the self‐assembly of micro‐ and nanoscale 3D architectures can be obtained by the shaping of initially planar structures . These shapeable material technologies have already demonstrated (Figure b) the capability to self‐assemble planar films into a number of different complex polygonal structures and tubular “Swiss‐rolls.”…”

Innovative Silicon Microgrippers for Biomedical Applications: Design, Mechanical Simulation and Evaluation of Protein Fouling

“…Among others, an untethered mobile microgripper controlled by an external electromagnetic coil system has been reported [4], where the manipulation of different microgels was successfully demonstrated with a pick-and-place robotic heterogeneous 3D assembly technique. A few more examples of microgrippers are present in the literature, piezoelectric [5,6] or thermally [7,8] or even magnetically actuated [8][9][10]. All these systems, however, present quite large dimensions and are not fully tested for working in a physiological environment, as required for biomedical applications.…”