Dissertation Defense: Jianhe Guo

High-Performance Artificial Micro/Nanomachines and Their Bioapplications

Jianhe Guo
Supervised by: Dr. Donglei Fan

Artificial micro/nanomachines are micrometer or nanometer scale mechanical devices that convert diverse energy sources into controlled mechanical motions. The development and applications of these micro/nanomachines are among the most pressing challenges in the research field of nanoscience and nanotechnology.

In this dissertation, we report innovative designs and operations of artificial micro/nanomachines for bioapplications in biochemical sensing, biomolecule capture, drug delivery and release. Based on the electric tweezers, innovative rotary nanomotors are bottom-up assembled with high efficiency from nanoscale building blocks, which are massively fabricated and less than 1 μm in all dimensions. After assembling, the rotary nanomotors achieve an ultrafast speed up to 18,000 rpm, an ultradurable operation lifetime of 80 hours, and over 1.1 million rotation cycles. To explore diverse alternative energy input for nanomotors, we also applied electric tweezers in the guided manipulation of chemical nanomotors: the motions of chemical nanomotors are aligned along the direction of AC electric fields and their speeds are modulated by the DC electric fields. The prowess of the manipulation of chemical nanomotors by the electric tweezers is demonstrated for applications in cargo delivery to designated microdocks and assembling of chemical nanomotors for powering rotary nanoelectromechanical system (NEMS) devices. To integrate the function of Raman sensing on the micro/nanomachines, plasmonic nanomotors and bio-photonic-plasmonic micromotors with silver (Ag) nanoparticle coating are designed and fabricated, which provide ultrasensitive detection of biochemicals by Surface-enhanced Raman spectroscopy (SERS). The plasmonic nanomotors are designed with nanoporous superstructures, which provide high capacities of drug loading and large numbers of hotspots. The plasmonic nanomotors also actively manipulate molecules and tune the release rate in electric fields due to the induced electrokinetic effect. The bio-photonic-plasmonic micromotors based on biosilica diatom frustules are applied in the capture and detection of DNA molecules, which are significantly accelerated during the rotation of the micromotors. The fundamental mechanism is investigated and attributed to the reduction of Nernst diffusion layer caused by the rotation. The innovations of artificial micro/nanomachines including concept, design, fabrication, manipulation, and bioapplications in this dissertation, are expected to inspire various research areas including NEMS, nanorobotics, microfluidics, biochemical delivery, and diagnostic sensing.