Miniaturization of the power source and on-board actuation is the main bottleneck for development of microscale mobile robots. As a possible solution, this paper proposes the use of flagellar motors inside the intact cell of Serratia marcescens bacteria for controlled propulsion of swimming robotic bodies. The feasibility of the proposed idea is demonstrated by propelling 10 µm polystyrene beads at an average speed of s m µ 6 15 ± by several bacteria randomly attached on their surface. On/off motion control of the bead is achieved by introducing copper ions to stop the bacteria flagellar motors and ethylenediaminetetraacetic acid to resume their motion.

Flagellated chemotactic bacteria have been utilized as actuators for propulsion of polystyrene microbeads by randomly attaching several bacteria on their surface. In this work, a plasma-based bacteria patterning technique is developed and used to limit bacteria attachment to approximately half of the microbead’s surface. Consequently, the effect of quantity and configuration of the attached bacteria on propulsion speed is studied experimentally. It is shown that the correlation between the propulsion speed and the number of bacteria is a strong function of the configuration of the bacteria and it follows one of the two distinct trends quantified by the proposed stochastic model.

Miniature and energy-efficient propulsion systems hold the key to maturing the technology of swimming microrobots. In this paper, two new methods of propulsion inspired by the motility mechanism of prokaryotic and eukaryotic microorganisms are proposed. Hydrodynamic models for each of the two methods are developed, and the optimized design parameters for each of the two propulsion modes are demonstrated. To validate the theoretical result for the prokaryotic flagellar motion, a scaled-up prototype of the robot is fabricated and tested in silicone oil, using the Buckingham PI theorem for scaling. The proposed propulsion methods are appropriate for the swimming robots that are intended to swim in low-velocity fluids. Transactions of the ASME Downloaded From: http://dynamicsystems.asmedigitalcollection.asme.org/ on 05/31/2015 Terms of Use: http://asme.org/terms

Cancer drug delivery remains a formidable challenge due to systemic toxicity and inadequate extravascular transport of nanotherapeutics to cells distal from blood vessels. It is hypothesized that, in absence of an external driving force, the Salmonella enterica serovar Typhimurium could be exploited for autonomous targeted delivery of nanotherapeutics to currently unreachable sites. To test the hypothesis, a nanoscale bacteria‐enabled autonomous drug delivery system (NanoBEADS) is developed in which the functional capabilities of the tumor‐targeting S. Typhimurium VNP20009 are interfaced with poly(lactic‐co‐glycolic acid) nanoparticles. The impact of nanoparticle conjugation is evaluated on NanoBEADS' invasion of cancer cells and intratumoral transport in 3D tumor spheroids in vitro, and biodistribution in a mammary tumor model in vivo. It is found that intercellular (between cells) self‐replication and translocation are the dominant mechanisms of bacteria intratumoral penetration and that nanoparticle conjugation does not impede bacteria's intratumoral transport performance. Through the development of new transport metrics, it is demonstrated that NanoBEADS enhance nanoparticle retention and distribution in solid tumors by up to a remarkable 100‐fold without requiring any externally applied driving force or control input. Such autonomous biohybrid systems could unlock a powerful new paradigm in cancer treatment by improving the therapeutic index of chemotherapeutic drugs and minimizing systemic side effects.

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