Imperceptible biointerfaces enabled by hydrogel-elastomer-based conductive nanomembranes

Soft bioelectronics hold immense potential across diverse applications, notably in healthcare, humanmachine interfaces, and conformal neural interfaces.A core driving force is the pursuit of high-fidelity, seamless integration between electronic systems and biological tissues, enabling the long-term stable monitoring of biosignals and precise diagnosis and therapy within closed-loop configurations.The past decade has seen transformative growth in this field, yielding numerous novel conformal integration strategies.These include seminal developments such as ultra-thin epidermal electronics [1,2], conformal bioelectronics fabrication or encapsulation using viscoplastic effect [3,4], and a "drop-printing" strategy for damage-free, conformal wrapping of bioelectronic interfaces through dynamic stress release [5].However, a fundamental trade-off in the clinical translation of bioelectronics lies between practical handleability ex vivo (pre-implantation) and the demand for mechanical conformability in vivo [6].To realize imperceptible biointerfaces-platforms avoiding mechanical stress or chronic tissue compression-devices must be nanoscale-thin and ultrasoft.Yet, such nanofilms are fragile and difficult to manipulate during conventional microfabrication and transfer steps, impeding their clinical translation and scalability.Now, writing in Nature Nanotechnology, Son, Kim and colleagues [7] report a transformable and imperceptible hydrogel-elastomer adhesive bilayer based on ionic-electronic conductive nanomembranes (THIN) that elegantly resolves the fundamental trade-off between device handleability and mechanical conformability.This work shifts the design paradigm from static mechanical matching to dynamic, stimuliresponsive mechanical decoupling.THIN is fabricated via an orthogonal solvent spin-coating process, forming a 350-nm-thick bilayer heterostructure, composed of a 90 nm hydrophobic semiconducting elastomer (poly(2-(3,3′-bis(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)-[2,2′-bithiophen]-5)yl selenophene) (P(g2T2-Se)) layer and a 260 nm hydrophilic adhesive hydrogel (catechol-conjugated alginate (Alg-CA)) layer (Figure 1a).This design leverages the dynamic mechanical response of the Alg-CA layer to resolve the conflict between device fabrication and biological application.In the dry state, a high Young's modulus of 1.35 GPa provides structural integrity, ensuring compatibility with standard microfabrication processes.Upon contact with