Bioadhesive and conductive hydrogel-integrated brain-machine interfaces for conformal and immune-evasive contact with brain tissue

•BMI is obtained by a self-setting process of hydrogel on microelectrode array •The hydrogel is bioadhesive, ensuring seamless contact with brain tissue •The hydrogel is ultrasoft, being mechanically compatible with soft brain tissues •The hydrogel is immune-evasive, being suitable for long-term implantable BMI Brain-machine interfaces (BMIs) enable communication between the brain and external machines. However, mechanical and biological mismatches, as well as weak physical adhesion-induced shifts between rigid electronic devices and soft brain tissue, generally trigger a host immune response, affecting signal recording and reducing the lifespan of BMIs in clinics. Herein, we design a bioadhesive ultrasoft BMI based on integration of bioelectronics with a dopamine methacrylate-hybridized poly(3,4-ethylenedioxythiophene) nanoparticle (dPEDOT NP)-incorporated hydrogel with high conductivity. The hydrogel exhibits robust adhesiveness, enabling tight integration with metallic microcircuits and seamless adhesion to the brain tissue. Most importantly, the hydrogel exhibits a brain-level modulus that reduces its mechanical discrepancy with brain tissue. Meanwhile, the hydrogel possesses immune-evasive ability, which actively prevents fibrous tissue encapsulation and neuroinflammation after implantation. Consequently, the immune-evasive, bioadhesive, ultrasoft, and conductive hydrogel-integrated BMI permits long-term and accurate electroencephalographic signal acquisition and communication with minimal foreign body reaction. Brain-machine interfaces (BMIs) enable communication between the brain and external machines. However, mechanical and biological mismatches, as well as weak physical adhesion-induced shifts between rigid electronic devices and soft brain tissue, generally trigger a host immune response, affecting signal recording and reducing the lifespan of BMIs in clinics. Herein, we design a bioadhesive ultrasoft BMI based on integration of bioelectronics with a dopamine methacrylate-hybridized poly(3,4-ethylenedioxythiophene) nanoparticle (dPEDOT NP)-incorporated hydrogel with high conductivity. The hydrogel exhibits robust adhesiveness, enabling tight integration with metallic microcircuits and seamless adhesion to the brain tissue. Most importantly, the hydrogel exhibits a brain-level modulus that reduces its mechanical discrepancy with brain tissue. Meanwhile, the hydrogel possesses immune-evasive ability, which actively prevents fibrous tissue encapsulation and neuroinflammation after implantation. Consequently, the immune-evasive, bioadhesive, ultrasoft, and conductive hydrogel-integrated BMI permits long-term and accurate electroencephalographic signal acquisition and communication with minimal foreign body reaction.