Collective guiding of acoustically propelled nano- and microparticles

Abstract

One of the most important potential applications of motile nano- and microdevices is targeted drug delivery. To realize this, biocompatible particles that can be guided collectively towards a target inside a patient's body are required. Acoustically propelled nano- and microparticles constitute a promising candidate for such biocompatible, artificial motile particles. The main remaining obstacle to targeted drug delivery by motile nano- and microdevices is to also achieve a reliable and biocompatible method for guiding them collectively to their target. Here, we propose such a method. As we confirm by computer simulations, it allows for the remote guiding of large numbers of acoustically propelled particles to a prescribed target by combining a space- and time-dependent acoustic field and a time-dependent magnetic field. The method works without detailed knowledge about the particle positions and for arbitrary initial particle distributions. With these features, it paves the way for the future application of motile particles as vehicles for targeted drug delivery in nanomedicine.

Fig. 1. (a–e) Illustration of the proposed particle guiding method. (f) Illustration of a single particle suitable for targeted drug delivery.

Fig. 2. Time evolution of a distribution of N_p = 1000 particles with diameter σ = 100 nm in the (a) x–y plane and (b) x–z plane with a homogeneous environment. Panels 1–5 show the particle distribution for increasing times, where the particles are enlarged by a factor 2000 to be visible. For 4 representative particles, also their trajectories are shown. Panels 6 show the radial particle distribution n(r,t) denoting the mean packing density at a distance r from the target (bin width 50 μm) at time t, the corresponding 70% quantile, the boundary of the target area, and the fraction of particles Φ(t) that are within the target at time t, ensemble averaged for 100 simulations.

Fig. 3. Analogous to Fig. 2, but now for a complex environment given by a network of channels with diameter 500 μm to which the particles are confined.

Fig. 4. The same channel system as shown in Fig. 3. In addition to the channels, we here show the axes of the channels that form a network.