In vitro electrochemical assessment of electrodes for neurostimulation in roach biobots.

Biobotics investigates the use of live insects as biological robots whose locomotion can be controlled by neurostimulation through implanted electrodes. Inactivity in the biobots (biological robots) can sometimes be noticed following extended neurostimulation, partly owing to incompatibility of implanted electrodes with the biobotic application or gradual degradation of the tissue-electrode interface. Implanted electrodes need to sufficiently exhibit consistent, reliable, and stable performance during stimulation experiments, have low tissue-electrode impedance, facilitate good charge injection capacity, and be compact in size or shape. Towards the goal of finding such electrodes suitable for biobotic applications, we compare electrochemical performances of five different types of electrodes in vitro with a saline based electrolytic medium. These include stainless steel wire electrodes, microfabricated flexible gold electrodes coated with PEDOT:PSS conductive polymer, eutectic gallium indium (EGaIn) in a tube, and "hybrid" stainless steel electrodes coated with EGaIn. We also performed accelerated aging of the electrodes to help estimate their longitudinal performance. Based on our experimentation, microfabricated electrodes with PEDOT:PSS and stainless steel electrodes coated with EGaIn performed remarkably well. This is the first time conductive polymer and liquid metal electrodes were studied comparatively for neurostimulation applications. These in vitro comparison results will be used in the future to provide a benchmark for subsequent in vivo tests with implanted electrodes in cockroach biobots.

Preliminary statistical assessment towards characterization of biobotic control.

Biobotic research involving neurostimulation of instrumented insects to control their locomotion is finding potential as an alternative solution towards development of centimeter-scale distributed swarm robotics. To improve the reliability of biobotic agents, their control mechanism needs to be precisely characterized. To achieve this goal, this paper presents our initial efforts for statistical assessment of the angular response of roach biobots to the applied bioelectrical stimulus. Subsequent findings can help to understand the effect of each stimulation parameter individually or collectively and eventually reach reliable and consistent biobotic control suitable for real life scenarios.

Kinect-based system for automated control of terrestrial insect biobots.

Centimeter scale mobile biobots offer unique advantages in uncertain environments. Our previous experimentation has demonstrated neural stimulation techniques in order to control the motion of Madagascar hissing cockroaches. These trials relied on stimulation by a human operator using a remote control. We have developed a Kinect-based system for computer operated automatic control of cockroaches. Using image processing techniques and a radio transmitter, this platform both detects the position of the roach biobot and sends stimulation commands to an implanted microcontroller-based receiver. The work presented here enables repeatable experimentation and allows precise quantification of the line following capabilities of the roach biobot. This system will help refine our model for the stimulation response of the insect and improve our ability to direct them in increasingly dynamic situations.

Line following terrestrial insect biobots.

The present day technology falls short in offering centimeter scale mobile robots that can function effectively under unknown and dynamic environmental conditions. Insects, on the other hand, exhibit an unmatched ability to navigate through a wide variety of environments and overcome perturbations by successfully maintaining control and stability. In this study, we use neural stimulation systems to wirelessly navigate cockroaches to follow lines to enable terrestrial insect biobots. We also propose a system-on-chip based ZigBee enabled wireless neurostimulation backpack system with on-board tissue-electrode bioelectrical coupling verification. Such a capability ensures an electrochemically safe stimulation and avoids irreversible damage to the interface which is often misinterpreted as habituation of the insect to the applied stimulation.