Structurally isolated photoactuation of graphene-mixed temperature-responsive hydrogels in soft-rigid series structure

Abstract

This paper presents fabrication and actuation methods for a soft microrobot with a hybrid structure composed of soft microactuators and a rigid supporting body. This hybrid structure enables actuation of the microrobot with independent driving of multiple actuators to provide complex movement like that of living microorganisms. We use the temperature-responsive hydrogel poly(N-isopropylacrylamide) (PNIPAAm) as a soft microactuator. PNIPAAm swells with water at low temperature but shrinks at high temperature. This volume change thus allows PNIPAAm to be used as an actuator by controlling its temperature. We successfully fabricated the microrobot with its soft-rigid hybrid structure composed of PNIPAAm and rigid photoresist using a multilayered microfabrication process. In addition, we used a sacrificial layer process to release the fabricated microrobot from the substrate to allow it to move freely. To actuate the microrobot, we mixed PNIPAAm with graphene, which has a high photothermal conversion efficiency. The temperature of the soft actuator when mixed with graphene can be increased by irradiating it with light. Therefore, actuation of the microrobot is achieved by sequentially irradiating the microactuators with focused light. We present the fabrication, release and partial actuation of the microrobot to demonstrate the feasibility of the proposed microrobot with the soft-rigid hybrid structure in this paper.

Microgripper Using Soft Microactuators for Manipulation of Living Cells

“…BioResist with graphene was used as a light absorber to actuate this soft structure by near-IR laser irradiation. By using laser irradiation, local heating with single cell resolution (≈10 µm) can be realized, as shown in our previous studies [ 29 , 30 ]. The proposed microgripper can grip and release a single cell by switching the laser on and off, as shown in Figure 1 a. Additionally, thermal damage to the target cells caused by changing the ambient temperature can be avoided with local heating.…”

“…Thus, dextran adhered to the substrate during the patterning of the SU-8 and BioResist; however, dextran was removed by water after patterning. The detailed fabrication processes are as follows and as previously described [ 29 ].…”

A Review of Soft Microrobots: Material, Fabrication, and Actuation

“…This provides the foundation for developing stimulus-responsive soft microrobots. So far, soft microrobots with stimuli-responsive characteristics mainly react to three stimuli: temperature, [129,130] light, [63,131] and pH. [132] Constructed with stimuli-responsive soft materials, soft microrobots can provide timely feedback to the corresponding stimuli through controllable deformation and body recovery, achieving different functional needs, such as efficient motion, cargo capturing and release, drug delivery et al The representative stimuli-responsive soft materials used for soft microrobots include poly (N-isopropyl acrylamide) (PNIPAM), [69] liquid crystal elastics (LCEs), [32,133] alginate, acrylic acid (AA), [132] acryloyl 6-aminocaproic acid (A6ACA), [134] and poly(2-hydroxyethyl methacrylate (pHEMA).…”

Texturing to Dramatically Increase Thermal Deformation of Bilayer Film and Application to Actuator

“…Many actuators have been studied as the driving source for insect‐scale robots [2,3] and micro‐mechanisms [4,5]. These actuators require smaller, lighter, and larger deformations.…”