Other startups trying to crack the code on needle-free blood sugar monitoring include Synex Medical, which in September raised $22 million, and HME Square, which uses photoacoustics, a technique that combines the principles of optics and acoustics to image biological tissues (such as blood).

In 2021, GraphWear raised a $20.5 million Series B for developing technology that can fit into a watch. The company hasn’t provided any public updates on its scientific progress since then.