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In this project, we have developed magnetically controlled untethered miniaturized devices that are capable of delivering electric output to induce electrochemical reactions for biological and environmental applications. During the project, we completed several tasks:

(a) Development of magnetic and piezoelectric materials and their integration in micro- and nanorobotic devices:

(b) Development of a magnetic setup for device manipulation, wireless magnetoelectric stimulation of small-scale devices

(c) Evaluation and verification of the magneto-electro-chemical processes in solutions, and application of the materials and devices for biomedical and environmental purposes.

Our study proved that the magnetoelectric materials and devices that we developed have great potential in targeted drug delivery, cell stimulation and treatment of contaminated water. Developing magnetoelectric materials was the first crucial step in this project. Biphasic composites, which include one magnetostrictive phase and one piezoelectric phase, are developed to obtain magnetoelectric behavior. The magnetostrictive materials and ferromagnetic shape memory alloys developed in our group include FeCo (ACS Appl. Mater. Interfaces 2015, 7, 7389; Electrochem. Commun. 2017, 76, 15), FeRh (Electrochim. Acta 2016, 194, 263), NiMnGa (Electrochim. Acta 2016, 204, 199), FeGa (Adv. Mater. 2017, 29, 1605458), FePd (Adv. Funct. Mater. 2018, 1705920), FeMnGa (unpublished). Piezoelectric materials including BaTiO3 (Mater. Horiz. 2016, 3, 113), ZnO, 0.5Ba(Zr0.2Ti0.8)O3]-0.5[(Ba0.7Ca0.3)TiO3](BZT-BCT) were developed through either sol-gel or hydrothermal synthesis or physical vapor deposition. Organic piezoelectric materials such as PVDF are also incorporated into the device (Adv. Mater. 2017, 29, 1605458). Single phase multiferroic materials such as BiFeO3 were also synthesized (iScience, 2018, 4, 236).

Depending on the final application and processability of selected materials, we designed micro- and nanodevices with different configuration and integrated the materials that we developed onto these devices. We took the first step to develop a magnetoelectric micromachine prototype by integrating magnetoelectric materials in a Janus microparticle design. This work enlightened the concept of highly-integrated micromachines with a simplified manipulation system (Mater. Horiz. 2016, 3, 113). Upon the first successful trial, we developed our microdevices according to three different applications: targeted drug delivery, cell stimulation and delivery, and water remediation. For targeted drug delivery, we first designed and fabricated FeGa@P(VDF-TrFE) core-shell magnetoelectric nanowires. The nanowires were able to release in vitro an anticancer drug and kill cancer cells using magnetoelectricity while minimizing the premature release of drug during transport. (Adv. Mater. 2017, 29, 1605458). We have also demonstrated for the first time planar undulations of composite multilink nanowire-based chains induced by a planar-oscillating magnetic field (Nano Lett. 2015, 15, 4829). Then we applied this configuration to a segmented nanowire device composed of a magnetic head and a piezoelectric tail. Depending on the oscillating frequency, the segmented nanowire can either swim or release the drug loaded on its surface (Adv. Funct. Mater., 2019, 1808135).

For cell stimulation, we have first demonstrated the idea of investigating the piezoelectric polymer PVDF for wireless neuronal differentiation (Sci. Rep. 2017, 7, 4028). Then we applied the piezoelectric materials on the microdevices. We fabricated microhelical devices based on composites consisting of piezoelectric polymers and magnetic nanoparticles. The devices can be driven to transport the neuron cells, and then trigger the differentiation by electrical stimulation (to be submitted). We also adopted the idea of remote electrical stimulation to bone cells. By using the template-based method, we fabricated magnetoelectric 3D scaffolds. Under magnetoelectric stimulation, the bone cells are likely to proliferate twice faster than the ones without magnetoelectric stimulation (to be submitted).

For water remediation, we first started by combining the photocatalytic materials such as Bi2O3/BiOCl and TiO2 with microrobots to study the feasibility of integration of oxides on microrobotic devices (J. Mater. Chem. A, 2015, 3, 23670; Adv. Funct. Mater., 2016, 26, 6995). Meanwhile, these photocatalytic systems also provided us references as we evaluate the performance of our magnetoelectric water remediation. Then we studied BiFeO3 (BFO), a magnetoelectric multiferroic bearing both magnetism and piezoelectricity, for water remediation. (iScience, 2018, 4, 236). We also developed CFO-BFO core-shell nanostructure and studied its magneto-electro-chemical effects. We found that they can efficiently degrade organic pollutants that cannot be degraded by ozone (Adv. Mater., under revision).