Bistable, Pneumatically Actuated Microgripper Fabricated Using Two‐Photon Polymerization and Oxygen Plasma Etching

Abstract

Fabrication of actuatable micromechanisms onto the tip of submillimeter medical instruments permits microsurgery, cellular‐level intervention, targeted drug delivery, or placement of microimplants. In these systems, a common lack of integrated microsensors or optical feedback prohibits stabilizing closed‐loop control. Moreover, the low stiffness of compact actuator and microfabrication limitations lead to difficult control. Herein, a compact bistable open‐loop micromechanism mounted on a small (170 μm) capillary fiber is developed. Bistabillity is utilized to control the mechanism to precise positions without the need for feedback or continuous control. Repeatable fabrication of this compact and high‐resolution bistable micromechanism is achieved with a two‐photon polymerization (2PP) process refined by oxygen plasma etching (OPE) that results in minimal feature size of a few hundred nanometers along the direction of the laser's axis, allowing 2PP bistable mechanisms to be fabricated in arbitrary orientations not restricted by printing direction. Finite element method simulations and experimental studies of the OPE effect are presented and used to optimize the micromechanism's bistable behavior. Finally, the feasibility of such compact bistable mechanism with a gripper that captures 50 μm spheres and passively maintains grasping without constant driving force even in long open‐close cycles is demonstrated.

Direct laser writing-enabled 3D printing strategies for microfluidic applications

“…8f). 216 For applications that rely on the capacity to deliver fluids via esDLW-printed components, Acevedo et al presented an approach for DLW-printing microfluidic structures with arbitrary geometries directly onto 360 μm-in-diameter fused silica tubes (Fig. 8g).…”

“…217 Key drawbacks of the these approaches, however, stem from the need for custom-built capillary holders to support loading into the DLW 3D printer. [215][216][217] Not only must each individual capillary be loaded into the holder manually (i.e., by hand), but in cases with high numbers of capillaries, it can be difficult to maintain consistent surface heights and axial orientations for each capillary. As a result, the alignment protocols required for each individual capillary-which are typically performed manually (i.e., by hand/eye under brightfield microscopy)prior to initiation of the DLW printing process can be exceedingly time and labour intensive.…”

Recent Advances in Multi‐Photon 3D Laser Printing: Active Materials and Applications

“…Power et al expanded this system in 2023 toward grippers which showed bistable behavior (see Figure 6C). [163] By oxygen plasma etching, the authors achieved 400 nm thin substructures in their chevron-style bistable gripper design able to undergo structural changes toward pressure changes. Alsharhan et al combined printed pneumatically actuated grippers with printed transistor structures.…”

“…Adapted with permission. [ 163 ] Copyright 2023, The Authors. D) SEM image of a spinneret which was printed inside of a microfluidic channel structure.…”

A 3D-printed bistable electromagnetic microlens actuator

“…To the best of our knowledge, the first example of a 3D nanoprinted magnetically actuated optomechanical device was recently demonstrated by Rothermel et al, 11 where ferromagnetic fluids were capillary-filled into integrated microchannels to achieve translational and rotational displacement of a micro-optical component using an external magnetic field. Also, Power et al 12 introduced a 3D nanoprinted bistable microgripper with pneumatic actuation that operates without continuous power consumption or closed-loop control.…”