Progress in wearable computing, bioelectronics, and physical human-machine interaction depends on new classes of electronics that match the mechanical properties of natural human tissue. This is accomplished with filled elastomer composites, soft microfluidics, and stretchable thin-film circuits with deterministic structures.
Soft Microfluidic Circuits & Sensors
Soft microfluidic circuits and sensors are composed of silicone (polydimethylsiloxane) elastomers embedded with microchannels of liquid metal (LM). The LM is a gallium alloy eutectic that is nontoxic and oxidizes in air to form a leak-resistant skin. Because the Ga alloy is liquid at room temperature, it remains intact and conductive as the surrounding elastomer is deformed during stretching, compression, or shearing.
B. A. Gozen, A. Tabatabai, O. B. Ozdoganlar, C. Majidi, “High-Density Soft-Matter Electronics with Micron-Scale Line Width,” Advanced Materials 26 5211-5216 (2014). [link]
A. Fassler, C. Majidi, “3D Structures of Liquid-Phase GaIn Alloy Embedded in PDMS with Freeze Casting,” Lab on a Chip 13 4442-4450 (2013).
A. Tabatabai, A. Fassler, C. Usiak, C. Majidi, “Liquid-Phase Gallium-Indium Alloy Electronics with Microcontact Printing,” Langmuir 29 6194-6200 (2013).[link].
A. Fassler, C. Majidi, “Soft-matter capacitors and inductors for hyperelastic strain sensing and stretchable electronics,” Smart Materials and Structures 22 055023 (2013).[link].
J. Wissman, C Majidi, “Soft-matter electronics with stencil lithography,” IEEE Sensors Baltimore, MD (2013).
P. Roberts, D. D. Damian, W. L. Shan, T Lu, C Majidi, “Soft-Matter Capacitive Sensor for Measuring Shear and Pressure Deformation,” IEEE International Conference on Robotics and Automation (ICRA) Karlsruhe, Germany (2013).
Our modeling efforts have primarily focused on the collapse of channels in soft microfluidic systems. Theoretical predictions for the change in microfluidic geometry under far-field loading are derived using theories in elasticity, fracture mechanics, and contact mechanics. These models are validated with experimental testing and, when appropriate, finite element modeling.
D. Tepayotl-Ramirez, Tong Lu, Y.-L. Park, C. Majidi, “Collapse of triangular channels in a soft elastomer,” Applied Physics Letters 102 044102 (2013).[link]
Y.-L. Park, D. Tepayotl-Ramirez, R. J. Wood, C. Majidi, “Influence of cross-sectional geometry on the sensitivity and hysteresis of liquid-phase electronic pressure sensors,” Applied Physics Letters 101 191904 (2012). [link]