Wearable Sensor Production Technique Replaces Photolithography
UC Berkeley engineers have come up a new technique for creating wearable sensor prototypes much faster and cheaper than existing methods.
Engineers from UC Berkeley have developed a new technique for creating stretchable, wearable sensors that allow medical researchers to prototype designs faster and at lower costs than traditional manufacturing methods. The technique replaces the traditional photolithography method in favor of a vinyl cutter, which proposes to save both time and money when prototyping.
Most wearable sensors in the medical field are used to gain data over extended time periods and usually come in adhesive bandages or as implants. These designs typically pack flat wires known as interconnects, along with sensors, power sources and antennas to transmit the collected data wirelessly. Moreover, their stretchable designs elicit the photolithography method of manufacturing to produce zigzag patterns on a thin substrate that can be extended and retracted with minimal degradation. It’s also expensive to produce.
To maintain that flexibility but significantly reduce costs, the scientists incorporated an “island-bridge” structure. Those islands are rigid platforms that house electronics, sensors, and other components linked by flexible bridges. The team made their wearable, flexible sensors by attaching PET (Polyethylene Terephthalate) to a mylar substrate. They then used a vinyl cutter to shape them and create two kinds of cuts – a tunnel cut, which slices through the top PET layer but leaves the Mylar substrate untouched, and a through cut that carves through both layers.
Tunnel cuts are used to trace the path of the interconnects. Those cuts are then peeled off, leaving the interconnect patterns on the mylar substrate. The entire sheet is then coated with gold, leaving the mylar surface with well-defined interconnects and exposed openings that serve as contact pads for connecting sensors or other islands. The engineers designed a pair of devices to demonstrate the new technique, including one that mounts under the nose and monitors breathing via temperature and another outfitted with water-resistant supercapacitors for quickly recharging devices in adverse conditions.