Electronics with switchable flexibility for 3D conforming neural interfaces.

The intricate cortical folds of large primates physically restrict access to substantial portions of neural information via interface devices. Here, we develop a bioelectronic system, sFlex-Fold, with switchable flexibility, representing the neural interface capable of nondestructive three-dimensional (3D) access to both cortical gyri and sulci, providing large-area, nonpenetrative deep tissue coverage. sFlex-Fold is based on an artificial intelligence (AI)-designed liquid metal alloy (LM-alloy), leveraging the phase change of the tailor-made LM-alloy to create neural interfacing electronics with tunable mechanical response to temperatures ranging from 25° to 37°C. The LM-alloy can be patterned into arbitrary circuit layouts with an ~10-micrometer resolution. The flexibility switching happens at the LM melting point, fine-tuned to 36.2°C, upon in vivo tissue contact, causing a three-order-of-magnitude reduction in the effective modulus of the implanted device. As a result, sFlex-Fold has the unique advantages of both a rigid and flexible state and can be morphed into complex, folded, 3D shapes. This enables nondestructive in vivo implantation into deep cortical sulci while maintaining large coverage (>80 square centimeters) over curved brain surfaces with tissue-matching mechanical compliance. Such 3D structural and mechanical mimicking enables high-quality electrical interfacing as quantitatively assessed using rodent and porcine models.