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Title: Micromanipulator on the tip of a fibre : fabrication and analysis
Author: Power, Maura
ISNI:       0000 0004 7969 8965
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2019
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The development of microrobots is motivated by their potential to enable therapies and procedures that are currently not possible. Miniaturising conventional robot designs to micro-scales, however, is not feasible due to scaling laws and the difficulties in fabrication and assembly. MEMS (Microelectromechanical System) fabrication techniques are the gold standard for devices such as microgrippers, although they are rarely intended for in vivo applications due to constraints on their form-factor. A common embodiment of medical microrobots in the literature are untethered swimming- or crawling-type microrobots that are designed to navigate through the body or for use in microfluidic devices. Alternative tethered microsurgical tools, beyond MEMS, are underrepresented in the literature, while untethered microrobots have experienced a great progression over the last decade. One technology that has aided in many of the advances in microrobotics is two-photon polymerisation (2PP); a 3D printing technology with sub-micron resolution. 2PP is a highly versatile fabrication technique that has already proven itself to be adaptable to a wide range of applications including optics, metamaterials and microrobots. This thesis explores how 2PP could be used to create novel tethered microrobotic tools that are fabricated on fibres (both standard silica-based fibres and more advanced multimaterial fibres). Multichannel fibres (capable of delivering light, electric current, gas, liquids etc.) are a promising platform upon which to fabricate and interface with 2PP-printed end-effectors in order to incorporate both actuation and sensing capabilities. A fabrication protocol for 2PP-printed end-effectors on fibres was developed. Passive-compliant end-effectors were used for both manual and automatic manipulation of microobjects in a closed-chain configuration. Real-time force sensing was incorporated, first using visually-inferred information and then, improving upon this, using an integrated interferometric force-sensing element. A 3-fingered passive-compliant gripper, on the tip of an optical fibre, with this force sensor was fabricated, validated and used in manipulation tasks. Finally, two active-compliant pneumatically-actuated mechanisms on a hollow capillary fibre were demonstrated: a piston with continuous motion and a bistable gripper. The two approaches were characterised, and the bistable gripper was demonstrated to grasp and hold a microbject in its closed state (without holding power) before release.
Supervisor: Yang, Guang-Zhong Sponsor: Imperial College London ; Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral