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We proposed a simple microfluidic device that enabled anisotropic absorption of detoxified S.typhimurium bacteria to microcubics so that the particles can swim toward desirable direction by chemotaxis of the bacteria. The speed of the “bacteria-based microrobot” was ∼5um/sec which is faster than any prior demonstrations, leading to an effective drug delivery system.

We proposed a simple microfluidic device that enabled anisotropic absorption of detoxified S. typhimurium bacteria to each microcubic so that the particles can swim toward desirable direction by chemotaxis of the bacteria. The speed of the “bacteria-based microrobot” was ∼5 um/sec which is faster than any prior demonstrations, leading to an effective drug delivery system.

This paper presents a method of fabricating pulverized drug, Lapatinib (Tykerb®), loaded micro chambers made of a biodegradable polymer, poly (e-caprolactone) (PCL), for bacteria-based microrobots. The PCL is a biodegradable, biocompatible polymer which is approved by the U.S. Food and Drug Administration (FDA) for use in the implantable medical devices. Lapatinib is approved by the U.S. FDA for the treatment of advanced or metastatic breast cancer. In order to realize bacteria-based microrobots, selective bacterial adhesion is necessary which can enhance directional locomotion of the bacteria-based microrobots. The x-ray lithography process can be used for biodegradable polymer micromachining to fabricate structures with various shapes which can be applied for bacteria-based microrobots. A pulverized drug is used because a liquefied drug cannot be used for the x-ray lithography process. To fabricate pulverized Lapatinib loaded micro chambers, the PCL films are prepared by the solvent casting method and lamination process. Lapatinib is encapsulated between the PCL films by the screen printing method. The x-ray lithography process is then used for fabrication of micro chambers. The fabrication results indicate that the proposed method is appropriate for fabrication of biodegradable polymeric micro chambers encapsulated with the pulverized drug for bacteria-based microrobots.

Bacteria-based biomedical microrobots have been proposed to achieve effective localized drug delivery. To enhance a directional locomotion of bacteria-attached microsystem, structures with selective bacterial adhesion are necessary. Having different surface morphologies of microstructures is beneficial for selective attachments of bacteria. In this paper, a surface energy modification method for controlling bacterial adhesion on biodegradable-polymer structures is presented. This is achieved by controlling exposed doses of x-ray synchrotron irradiation. To calculate the x-ray exposure time for varying the surface morphology of the biodegradable polymeric devices, the equation for exposed dose is derived. The contact angles of different surfaces are measured, and the corresponding surface energies are calculated to verify the modification of the surface morphology. As a result, the surface energy increases with the increment of the exposed dose to the biodegradable-polymer. The developed surface energy modification method is suitable for modifying the polymeric surface without additional physical/chemical treatments. The fabricated cubic structures with different surface morphologies can be used for effectively flagellating bacteria on selective surfaces for directional locomotion.

Bacteria based biomedical micro-robot is being investigated or proposed to achieve effective and localized drug delivery system due to low toxicity and free of external power sources. In this work, we proposed a simple microfluidic system that enables anisotropic bacterial attachment to the drug containing micro chamber made of biodegradable polymer. A pin-ball type trapper can capture only one micro chamber at a fixed configuration. The efficiency of the trapper was analyzed by monitoring the motion of chambers. More than 70% of trapper was filled with the micro chamber within seconds, leading high throughput applications. We are planning to introduce modified Salmonella bacteria for absorbing them to the specific sides of the micro chamber. After releasing the chamber, one would use it as a microrobot by the chemotaxis of the attached bacteria towards the targeted site.

In order to provide high quality visual information to patients who have implanted retinal prosthetic devices, the number of microelectrode should be large. As the number of microelectrode is increased, the dimension of the microelectrode is decreased, which in turn results in the increased interface impedance of microelectrode and decreased dynamic range of injection current. In addition, the reduced maximum limit of injection current may not be sufficiently large to stimulate the ganglion cells in a retina. In order to improve the trade-off envelope between number of microelectrode and current injection limit, a 3D microelectrode structure can be used as an alternative. From the advancement of microfabrication technology, the fabrication of highly-accurate 3D structures with small dimensions is possible. This paper presents a first comprehensive electrical characterization of 2D and 3D microelectrodes for high-resolution retinal prostheses. Microelectrodes which differ in shapes and diameters are analyzed. Their interface impedances and charge injection limits are quantitatively analyzed. This research can be used to define requirements for further retinal prosthetic device research.

In this paper, a novel method of fabricating a drug-loaded, cubic micro-chamber made of biodegradable polymer for bacteria-based drug delivery is presented. A biodegradable polymer, poly-capro-lactone (PCL), is used to fabricate the micro-structure. The biocompatibility of PCL is approved by the Food and Drug Administration in U.S. for use in humans. To fabricate the drug-loaded cubic micro-chamber, laminated PCL films are prepared, and a drug is encapsulated between the films using the inkjet printing method. Generally, PCL cannot easy be micromachined by a conventional photolithography technique. Therefore, an x-ray lithography process is developed to fabricate the cubic structure. The fabrication results indicate that the proposed method is excellent for microfabricating drug-loaded cubic micro-chambers made of the biodegradable PCL polymer for bacteria-based drug delivery.

In this paper, the mechanical and electrical characteristics of 3D microelectrode are presented to provide the long-term stability of the implanted microelectrode. As the dimensions of the microelectrode become smaller, the microelectrode can be easily damaged by mechanical pressure and over-injected electric charge. In order to avoid these destructions, allowable mechanical and electrical stress should be determined. Experiments for durability evaluation are set up and performed to measure the mechanical force and safe charge injection limit. The result of the experiments shows that the allowable mechanical force in vertical and horizontal direction is 0.8165 N and 0.2068 N, respectively. In the charge injection test, it is observed that the density of injected charge is a prior factor in microelectrode dissolution rather than the total amount of injected charge.

This paper presents a biodegradable polymer droplet for efficient drug delivery using flagellated bacteria. The biodegradability and the localized delivery are the most important features for determining the efficiency of drug delivery. The proposed droplet is made of poly (DL-lactic-co-glycolic acid) for the biodegradability. It is fabricated using a microfluidic device which has a Y-junction microchannel. The fabricated biodegradable droplet has diameter in the range between 20 µm and 30 µm. Then flagellated bacteria, Serratia marcescens, are attached to these droplets for a localized drug delivery. The Serratia marcescens has a chemotaxis to tumor cells, and thus can be used as an actuation source of self-seeking to the tumor site. This paper presents the proposed concept, droplet fabrication, bacteria attachment, and observed rotational motion of the drug delivery methodology. The experimentally achieved maximum angular velocity is 0.11 rad/sec.