Nature volume 595, pages 532–536 (2021 )Cite this article
Nearly 50 years ago, Intel created the world’s first commercially produced microprocessor—the 4004 (ref. 1), a modest 4-bit CPU (central processing unit) with 2,300 transistors fabricated using 10 μm process technology in silicon and capable only of simple arithmetic calculations. Since this ground-breaking achievement, there has been continuous technological development with increasing sophistication to the stage where state-of-the-art silicon 64-bit microprocessors now have 30 billion transistors (for example, the AWS Graviton2 (ref. 2) microprocessor, fabricated using 7 nm process technology). The microprocessor is now so embedded within our culture that it has become a meta-invention—that is, it is a tool that allows other inventions to be realized, most recently enabling the big data analysis needed for a COVID-19 vaccine to be developed in record time. Here we report a 32-bit Arm (a reduced instruction set computing (RISC) architecture) microprocessor developed with metal-oxide thin-film transistor technology on a flexible substrate (which we call the PlasticARM). Separate from the mainstream semiconductor industry, flexible electronics operate within a domain that seamlessly integrates with everyday objects through a combination of ultrathin form factor, conformability, extreme low cost and potential for mass-scale production. PlasticARM pioneers the embedding of billions of low-cost, ultrathin microprocessors into everyday objects.
Unlike conventional semiconductor devices, flexible electronic devices are built on substrates such as paper, plastic or metal foil, and use active thin-film semiconductor materials such as organics or metal oxides or amorphous silicon. They offer a number of advantages over crystalline silicon, including thinness, conformability and low manufacturing costs. Thin-film transistors (TFTs) can be fabricated on flexible substrates at a much lower processing cost than metal–oxide–semiconductor field-effect transistors (MOSFETs) fabricated on crystalline silicon wafers. The aim of the TFT technology is not to replace silicon. As both technologies continue to evolve, it is likely that silicon will maintain advantages in terms of performance, density and power efficiency. However, TFTs enable electronic products with novel form factors and at cost points unachievable with silicon, thereby vastly expanding the range of potential applications.