Liquid metal printing is integral to the flexible electronics field. Additive manufacturing enables fast fabrication of intricate designs and circuitry. The field features a range of products including electrically conductive textiles; bendable displays; sensors for torque, pressure, and other types of strain; wearable sensor suits, such as those used in the development of video games; antennae; and biomedical sensors. Soft robots, flexible computer screens, and other stretchable electronic devices also can be created.
Additive manufacturing (3D printing) of tall, complicated structures can be accomplished with a highly conductive gallium alloy. Nickel nanoparticles were added into the liquid metal (galinstan) to thicken it into a paste with a consistency suitable for additive manufacturing. The runny alloy was impossible to layer into tall structures, but with a paste-like texture, it can be layered while maintaining its capacity to flow and to stretch inside rubber tubes.
Gallium alloys are already being used as the conductive material in flexible electronics. The alloys have low toxicity and good conductivity, plus they are inexpensive and “self-healing” — able to attach back together at break points. Prior to this new modification that uses sonication — the energy of sound — to mix the nickel particles and the oxidized gallium into the liquid metal, the alloys’ printability was restricted to two-dimensional. Structures up to 10 millimeters high and 20 millimeters wide were printed using this method.
The gallium alloy paste demonstrates several features new to the field of flexible electronics; namely, it can be made easily and quickly. Also, the structural change is permanent, the electrical properties of the paste are comparable to pure liquid metal, and the paste retains self-healing characteristics.