Thermoresponsive hydrogel with embedded magnetic nanoparticles for the implementation of shrinkable medical microrobots and for targeting and drug delivery applications

Abstract

The paper describes the choice of a thermoresponsive material for the implementation of untethered medical microrobots and other microdevices. These entities can be propelled at a specific location in the body using a Magnetic Resonance Imaging (MRI) system while being actuated for various functions such as the release of drugs by a volume change induced by hyperthermia of nanoparticles embedded in the hydrogel. This paper presents some preliminary results showing that poly(N-isopropylacrylamide) (PNIPA) might be an interesting choice, because of the important volume decrease when temperature is increased of some degrees. Using PNIPA based microparticles could be an interesting choice because, according to our results, volume changes are more important when the volume is smaller, and shrinking rate is higher when there are nanoparticles embedded in the hydrogel.

Open-Loop Magnetic Actuation of Helical Robots using Position-Constrained Rotating Dipole Field

“…where J m ∈ R n×n is the manipulator Jacobian. Mahoney and Abbott have shown that the velocity level kinematics (10) can also be modified to include the contri- bution of the magnetic moment of the actuator magnet using Ṁ = Ω × M, and we obtain [19] ẋ Ṁ = I 0 0 SK(M) J m (q) q = J A (q) q,…”

“…The locomotion of these tetherless devices capitalizes on the conversion of several forms of energies into mechanical energy or movement. Magnetic [5], [6], acoustic [7], chemical [8], electric [9], thermal [10], and light [11] energy have been utilized to actuate structures fabricated specifically to work upon sensing one, or a combination [12], of these external stimuli. Once the relation between the external energy and the behavior of the stimuli-responsive material in the fabricated structures is understood, a locomotion strategy is designed to work based on the environment and the potential application.…”

MILiMAC: Flexible Catheter With Miniaturized Electromagnets as a Small-Footprint System for Microrobotic Tasks

“…These agents are often designed with a specific surgical tasks in mind and fabricated using sophisticated techniques [2]. Prominent examples involve: soft grippers for single-cell biopsy [3], scaffold-type robots for stem cell manipulation [4], thermoactive polymers for targeted drug delivery [5], stress-engineered MEMS microrobots [6], tubular micromotors, such as spermbots or microjets [7], and helical microswimmers [8]. With recent advancements in soft materials and microfabrication techniques, the surge of new micro-agents is expected to continue [9].…”

Magnetic catheters : a journey across orders and scales

“…These agents are often designed with a specic surgical tasks in mind and fabricated using sophisticated techniques [104]. Prominent examples involve: soft grippers for single-cell biopsy [227], scaold-type robots for stem cell manipulation [228], thermoactive polymers for targeted drug delivery [229], stress-engineered MEMS microrobots [230], tubular micromotors, such as spermbots or microjets [231], and helical microswimmers [232]. With recent advancements in soft materials and microfabrication techniques, the surge of new micro-agents is expected to continue [233].…”