The Study Of Micromotors Based On Polymeric Microstructure

In biological systems, kinesin and other biological micromachine can use the energies from ATP hydrolysis and convert them into mechanical works to complete mass transfer within cells. Enlightened by the motion behavior in biological systems, researchers have developed man made micromachines similar to the biological ones. They exhibit autonomous movement based on the energy conversion from chemical fuels or external fields( magnetic, electric, etc.). These autonomous micromotor have potential applications in the fields of drug delivery, ion detection, microfluidic and so on. There are two different kinds of micromachines. Among others, the micromotor refers to the microdevices, which can move by themselves. The micropump is capable of driving the liquid in the surrounding environment. However, due to the limitation in the fabrication method, it is difficult to control the size and shape of the micromachines, which hinders the research on the relationship between the size/shape and the motion behavior of the micromachine. In addition, the stimuli responsive micromotor and micropump have not been realized. Based on the above-mentioned problems, we have utilized PDMS template to synthesized PCL microstructures with different sizes and shapes, which can be used for micromotor study. Furthmore, we have fabrication stimuli responsive micromotor and micropump based on the hydrogel.1. Size and shaped-controlled fabrication of polymer-based man made micromotor based on PDMS template1. Firstly, we use modified Micro-transfer molding technology based on PDMS template to synthesis solid PCL-Pt micromotor with various shapes and size. Due to the catalytic activity of the PtNPs, the resulting micromotors exhibit autonomous movement when placed in the hydrogen peroxide(H2O2) solution. In addition, various functional materials(Rhodamine fluorescent dyes and magnetically responsive iron oxide particles)can be introduced through the encapsulation method to make the micromotors versatile in functions, such as fluorescence and magnetic property. We also found that the shapes and sizes of micromotors can affect their motion behavior. In addition, by combining PDMS template and PVA sacrificial layer, we construct cup-shaped and stool-like microtransporters, which have hollow structures. After loading Pt nanoparticles at the bottom of the cup-shaped microtransporter, it exhibits the autonomous movement in a liquid environment. Importantly, microtransport can capture, transport and release PCL microspheres based on its cavity under the influence of the magnetic field without any surface modification. Furthermore, the stool-like microtransporter shows size selectivity during microsphere transportation. We thus believe the current method has potential applications in the fabrication of multiple functional micromachines.2. Preparation of stimuli-responsive artificial micromotor and micropumpWe have synthesized poly(N-isopropylarylamide) hydrogel motors which have thermal-responsive function and sodium polyacrylatehydrogel which has acid-responsive function. In both cases, an amphiphilic surfactant(Triton X-100) is encapsulated. In the presence of external stimuli(heat or acid), the crosslinked hydrogel shrinks. The surfactant will be released, reducing the local surface tension.Because of the Marangoni Effect, the hydrogel motor displaysautonomous movement. In addition, we construct a series of hydrogel-based micropump: pH-responsive micropump, calcium-responsive micropump, enzyme micropump and surfactant micropump. Preparation of these micromotors and pumps structure is very simple.The materials are readily available.Hydrogels also show goodbiocompatibility, We believe they are useful for the application, including detection, microfluidics, drug release and so on.