Stimuli-Responsive Actuator Fabricated by Dynamic Asymmetric Femtosecond Bessel Beam for In Situ Particle and Cell Manipulation

Abstract

Microscale intelligent actuators capable of sensitive and accurate manipulation under external stimuli hold great promise in various fields including precision sensors and biomedical devices. Current microactuators, however, are often limited to a multiple-step fabrication process and multimaterials. Here, a pH-triggered soft microactuator (<100 μm) with simple structure, one-step fabrication process, and single material is proposed, which is composed of deformable hydrogel microstructures fabricated by an asymmetric femtosecond Bessel beam. To further explore the swelling–shrinking mechanism, the hydrogel porosity difference between expansion and contraction states is investigated. In addition, by introducing the dynamic holographic processing and splicing processing method, more complex responsive microstructures (S-shaped, C-shaped, and tortile chiral structures) are rapidly fabricated, which exhibit tremendous expected deformation characteristics. Finally, as a proof of concept, a pH-responsive microgripper is fabricated for in situ capturing polystyrene (PS) particles and neural stem cells rapidly. This flexible, designable, and one-step approach manufacturing of intelligent actuator provides a versatile platform for micro-objects manipulation and drug delivery.

Tethered and Untethered 3D Microactuators Fabricated by Two-Photon Polymerization: A Review

“…Since the swelling factors of the hydrogels are closely related to the exposure dose, programming such a dose spatially on the Bessel ring leads to facile fabrication of anisotropic structures. Li generated a heterogeneous light field during the fabrication process, resulting in microtubes with asymmetric swelling/shrinking properties that exhibited reversible bending and reverting to an upright conformation within 1 s when the solution pH value changed (Figure 4b) [86]. He also demonstrated the application of this type of effective microgripper for trapping and releasing PS particles and neural stem cells.…”

“…As shown in Figure 4a, the distance between two adjacent rings can be varied from 11.4 μm to 7.2 μm such that objects with specific sizes can pass through or be intercepted selectively. [86], Copyright © 2020, American Chemical Society. (c) Complex 3D micro-umbrella, which can be constructed to achieve rapid, precise, and reversible articulated-lever folding by varied pH value.…”

Trends in Micro‐/Nanorobotics: Materials Development, Actuation, Localization, and System Integration for Biomedical Applications

“…The swarming behavior of the m‐bots not only broadens the scope of understanding related to self‐assembly behavior in natural living systems as introduced in Section 4.7, but also brings out the potential for applications such as the multiple cargo manipulation, [ 273,396,397 ] antidiffusion by the swarming m‐bots, [ 287 ] enhanced delivery capability ( Figure a), [ 398 ] reconfigurable adjustment of the energy delivery dose for enhanced magnetic hyperthermia (Figure 21b), [ 399,400 ] and cell alignment (Figure 21c) and manipulation of intracellular organelles. [ 401 ] The in vivo swarming behavior of biological and artificial m‐bots have been investigated and explored, and it has been verified that the collective motion behavior of micro‐/nanoagents can commonly realize the enhanced delivery of drugs and energy.…”

Two-photon polymerization nanolithography technology for fabrication of stimulus-responsive micro/nano-structures for biomedical applications

“…The use of stimulus-responsive photoresists for TPP has facilitated development of different micro/nano-actuators. Recently, Li et al [139] reported a pH-triggered soft microgripper (<100 μm) with four fingers using a poly (acrylic acid)-based hydrogel for capturing microparticles and cells. As discussed above, carboxyl (-COOH) in the side chain played an important role in the deformation triggered by a pH value change.…”