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Tong Lu — 2013-14 Fellow

Project Title: A Tissue-engineered Actuator Integrated with Conductive PDMS Electrodes

Project Description
Engineered tissue is natural tissue cultured and differentiated in artificial environments. Researchers are interested in engineered tissue because of its biological nature that is responsive to external stimulus. Some engineered tissues, such as myotubes, show contractility when stimulated by an electric field, and gives them the potential to be used in application like tissue-engineered actuators.

A typical tissue-engineered actuator consists of engineered myotubes and PDMS thin film. Myoblasts are placed on PDMS thin film by a microcontact print method and differentiated into myotubes in solution. A tissue-engineered actuator works in the mechanism as follow. The myotubes are attached to the PDMS thin film firmly. There is no stress in the myotubes in the absence of an electric field. When applying an electric field, a stress of about 1.8 kPa is generated in myotubes and this causes the deformation of PDMS thin film.

A lot of tissue-engineered actuators, including some bio-inspired actuators, have been developed by researchers. However, they are all actuated by an electric field generated by external electrodes, and this has limited their application in areas such as biomedical devices. The goal of this project is to design, model, and fabricate a tissue-engineered actuator integrated with electrodes so that it can be actuated by an on-board electric field. In this project, conductive PDMS (cPDMS) is selected as an electrode material, and a laser-patterning technique has been developed to realize rapid micron-scale surface patterning on cPDMS with no clean room needed. This technique is based on a laser engraver and can be applied in high-precision fabrication, if high-resolution laser is available.

This project is planned to be done in two phases. In Phase One, the mission is to find the proper design and right method to fabricate the electrodes. In Phase Two, the work will focus on integrating the electrodes with a tissue-engineered actuator. Some of the work of Phase One has been completed.

Phase One is mainly done by Prof. Carmel Majidi’s research group. First we analyzed how the electrodes influence the motion of the actuator, as well as the electrical characteristics of electrodes. The analysis results show that the thickness of the electrodes is the most important factor to be considered. Since the stress generated by tissue is very small, the electrodes must be thin enough so that it will not limit the deformation. cPDMS was selected as an electrode material and the laser-patterning technique, developed by us as mentioned, was chosen for fabrication. cPDMS, which is a mixture of carbon black particle and PDMS, shows stable conductivity. It can be spin-coated to form a very thin film, and this makes it suitable for laser-patterning. A film of PDMS is spin-coated on the electrodes to separate the electrodes from tissue. Some samples of cPDMS electrodes have been fabricated. In the rest of Phase One, we will work on optimizing the layout of electrodes and reducing the dimensions of electrodes.

In Phase Two, we will integrate the tissue-engineered actuator with electrodes by culturing myoblasts directly on the PDMS film of electrode. This work will be done mainly by Prof. Adam Feinberg’s research group. The tissue-engineered actuators integrated with cPDMS electrodes will be connected to a voltage supply to test their performance. If they work as expected, we will design and fabricate tissue-engineered actuators with more complicated patterns and layouts, such as bio-inspired actuators, with the same method.

Tissue-engineered actuators have great potential to be used in artificial muscle because they are fast in response and biologically compatible. However, this application has been limited by the absence of an on-board electric field. This research aims to solve this problem and provides a new solution for artificial muscle. The tissue-engineered actuators integrated with electrodes are promising in biomedical engineering, and they can be applied in artificial organs, such as artificial cardiac valve.