Investigators: Zheng Chen, Yang Fang, Alex Will, Stephan Shatara, Dan Laboy
Sponsors: National Science Foundation, MSU IRGP, and International Society for Optical Engineering (SPIE)
Collaborators: Dr. Mohsen Shahinpoor (Environmental Robots Inc./University of New Mexico), Dr. Gursel Alici (University of Wollongong, Australia), Dr. Kwang J. Kim (University of Nevada), Dr. Yantao Shen (Michigan State University), Dr. Ning Xi (Michigan State University)
Select publications:
Modeling of Actuation and Sensing
Micromanipulation and Biological Applications
Robotic Fish for Mobile Sensing
Electroactive polymers (EAPs), also informally known as Artificial Muscles, are a class of smart materials that show strong coupling between the applied electric field and their mechanical strains. We are particularly interested in two classes of EAPs, Ionic Polymer-Metal Composites (IPMCs) and Conjugated Polymers (in particular, Polypyrroles), since they produce large bending motions under low actuation voltages (about 1 V), are biocompatible and resilient, with tremendous potential in biomedical devices, micromanipulation, and biomimetic robotics. Click the following two pictures for video clips of graceful movements of an IPMC actuator and a Polypyrrole actuator, respectively.
The goal of this project is to fully realize the potential of these emerging actuation materials by
Modeling of Actuation and Sensing
Two real-time control stations, one based on DSpace and the other on RT Linux, are dedicated to the modeling, sensing, and control research. A laser distance sensor and a PVDF micro-force sensor are used to capture the actuation performances of EAPs. To investigate their behaviors as mechanical sensors, we have built an apparatus that can provide controllable, mechanical excitation to EAP samples. Click the following pictures to see video clips of the apparatus at work: left - the first prototype for proof of concept showing the generation of electrical signal from the artificial muscle; right - a sturdy metal-based version of the setup.
SML strives to make systems smaller. Sensing is often prohibitive for microsystems and nanosystems due to their limited real estate, and thus compact, accurate sensing schemes are of interest in the development of miniaturized systems. Several approaches are being investigated in our lab to detect the displacement/force generated by an EAP actuator in a way that takes no or very little extra space. One approach we have developed is to integrate a thin PVDF (polyvinylidene fluoride) film with an IPMC. As PVDF is an piezoelectric material, the IPMC/PVDF hybrid now functions as an actuator and sensor.
Micromanipulation and Biological Applications
One promising application area for EAPs is micromanipulation. We have built an IPMC-based micromanipulator and used it for micro-injection of fruitfly embryos. This operation, necessary for genetic modification of Drosophila embryos, has traditionally be performed manually, which is time-consuming with low yield. With sensory feedback from the PVDF layer, we expect to automate the injection process with accurate force and position control. Shown in the pictures below: an IPMC/PVDF equipped with a pipette (tip diameter 2 microns) ready for the injection experiment (left), and snapshots of the injection into a Drosophila embryo (right). Click the snapshots for a video (3 Mb) of the injection process. We are also investigating the use of such micromanipulators in biomechanical study of single cells.
Robotic Fish for Mobile Sensing
The goal is to develop an autonomous swimming robot propelled by EAP actuators. Without using motors, such a robotic fish will deliver noiseless and efficient locomotion. Advanced navigational capabilities, together with communication and sensing modules, will allow the robotic fish to carry out missions of practical interest, e.g., environmental monitoring and control, and reconnaissance in hostile waters.
We have developed two prototypes of robotic fish using IPMC actuators as caudal fins. The first one (left in the pictures below) was remotely controlled by a radio controller, while the second one (right) is capable of mesh networking. Equipped with microcontroller, Zigbee, GPS, and temperature sensor, the robot can serve as a mobile sensing platform. Ongoing research is focused on implementing localization module (without reliance on GPS) so that groups of such fish can be used for study of swarming behaviors. Click the pictures for video clips of fish in action.
