In this work, a Multiwalled Carbon Nanotube/poly(alkylthiophene) (MWCNT/PT) composite is developed as the electrodes for dielectric elastomer actuators (DEAs) using the Langmuir-Schaefer (LS) method. These composites form stable monolayers at the air-water interface that can then be LS transferred onto a poly(dimethylsiloxane) (PDMS) elastomer membrane. The monolayer electrode remains conductive up to 100% uniaxial strain. We present a method to fabricate DEAs using the LS transferred electrodes. By using a mask during the transfer step, the electrodes can be patterned with better than 200 m resolution on both sides of a 1.4 m-thick pre-stretched PDMS membrane to produce an ultra-low voltage DEA. The DEA generates 4.0% linear strain at an actuation voltage of 100 V, an order of magnitude lower than the typical DEA operating voltage.

We present a mechanically active cell culture substrate that produces complex strain patterns and generates extremely high strain rates. The transparent miniaturized cell stretcher is compatible with live cell microscopy and provides a very compact and portable alternative to other systems. A cell monolayer is cultured on a dielectric elastomer actuator (DEA) made of a 30 μm thick silicone membrane sandwiched between stretchable electrodes. A potential difference of several kV’s is applied across the electrodes to generate electrostatic forces and induce mechanical deformation of the silicone membrane. The DEA cell stretcher we present here applies up to 38% tensile and 12% compressive strain, while allowing real-time live cell imaging. It reaches the set strain in well under 1 ms and generates strain rates as high as 870 s−1, or 87%/ms. With the unique capability to stretch and compress cells, our ultra-fast device can reproduce the rich mechanical environment experienced by cells in normal physiological conditions, as well as in extreme conditions such as blunt force trauma. This new tool will help solving lingering questions in the field of mechanobiology, including the strain-rate dependence of axonal injury and the role of mechanics in actin stress fiber kinetics.

We developed an integrated device for measuring the Young's modulus of adherent cell monolayers over time within a physiological environment.

Test assays capable of providing quantitative characterization of the contraction of cardiac and smooth muscle cells are of great need for drug development and screening. Several methodologies have been proposed for achieving measurement of cell contractile stress or force, however almost all rely on optical methods to detect contraction. Recently, we proposed a test assay method based on the cell-induced deformation of thin-film, elastomeric, capacitive sensors. The method uses an electrical (capacitive) read-out enabling facile up-scaling to a large number of devices working in parallel for high-throughput measurements. We present here a model for the prediction and optimization of sensor performance. Our model shows the following trends: a) a cell region ratio of approximately 0.75 of the culture well radius produces the largest change in capacitance for a given cell contractile stress, b) the change in capacitance generated by cell contraction increases as the Young's modulus, sensing layer thickness and electrode thicknesses of the sensor decrease, following an inverse relationship. A prototype device is fabricated and characterized in cell culture conditions. Mean standard deviations as lows as 0.2 pF are achieved (< 0.05% of the initial sensor capacitance), representing a minimum detectable cell stress of 1.2 kPa, as predicted by our model. This sensitivity is sufficient to measure the contractile stress of smooth and cardiac muscle cell monolayers as reported in the literature.