A team of scientists creates ThreadSense to test their new touch sensing technique. The smart thread can detect touch locations. (Image credit: Dartmouth)


Touch sensing technology is becoming more common, and it’s continuously improving. A team of scientists from the University of Science and Technology in China, National Taiwan University, and Dartmouth College thinks they can make them even better. They created ThreadSense, a smart thread that’s able to locate up to two consecutive touches. The team initially developed the thread to test their new sensing technique for interactable threads.


The new technique they discuss in their latest research paper locates up to two touches using impedance sensing with a spacing resolution that hasn’t been used previously. Their method stands out because it’s based on a model-based approach, which determines touches with a mathematical model that describes the change in the impedance of the thread in relation to the touches. Unlike standard techniques, this new method doesn’t need to be trained and makes for easy calibration.


To test the method, the team created the ThreadSense prototype, which enables a thread made of conductive materials to locate user touches. Each end of the thread is connected to electrodes with a small AC current inserted between them. This allowed them to test the thread impedance. When a user touches the thread, it sends a small amount of current to ground, which increases the thread’s impedance measured at specific AC frequencies.


While the thread was able to detect single touches, they struggled to detect two concurrent touches due to environmental noises. This could affect the measure impedance, making it less reliable to locate touches. To address the issue, the team employed a frequency sweeping technique, which collects thread impedance measurements as the AC frequency is swept. They found the collected measurements were more robust against environmental noises.


Once that was solved, ThreadSense was implemented in four different applications: a braided headband that interacts with a computing device, a handsewn cushion that acts as a remote control, an interactive tulip bookmark to control ambient light while reading, and a headphone cable that allows you to quickly answer and record calls. Though the smart thread worked well in all the applications, ThreadSense isn’t quite ready for the consumer market. Researchers plan to keep working on the smart thread but remain confident it can be used for future touch applications in soft and thin materials.



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