3D-printed conductive polymer hydrogels enable implantable bioelectronics

Implantable bioelectronics can treat various medical conditions by interfacing with biological tissue. Conventional rigid electronics often damage tissue and fail due to mechanical differences. Researchers are investigating soft, flexible bioelectronics, with hydrogels showing promise due to their tissue-like properties. Recent work by Chinese researchers has developed 3D printable conductive polymer hydrogels that significantly advance the field.

The study, published in Advanced Functional Materials, describes a method for formulating inks for Direct Ink Writing (DIW), an extrusion-based 3D printing process. By adapting chemical components such as polyvinyl alcohol (PVA), chitosan (CTS) and a synthetic copolymer of poly(acrylic acid-co-acrylic acid-N-hydroxysuccinimide ester (PAA-NHS), the researchers developed inks for the different layers of hydrogel bioelectronics.

A remarkable property of these hydrogel bioelectronics is their ability to adhere instantly and firmly to various biological tissues such as skin, heart, blood vessels and nerves. This adhesion is achieved through a dry cross-linking mechanism that creates covalent bonds, hydrogen bonds and electrostatic interactions between the hydrogel and tissue surfaces. This strong bioadhesion is crucial to ensure a seamless and stable connection during the dynamic movements of living tissues, such as the heartbeat.

The team tested the effectiveness of their 3D-printed hydrogel bioelectronics in electrophysiological studies on rat hearts. The bioelectronics adapted perfectly to the surface of the beating heart without disturbing the natural rhythm. The devices enabled precise mapping of epicardial electrophysiological signals and successfully identified abnormalities associated with cardiac arrhythmias and myocardial infarction. In addition, the hydrogel bioelectronic devices were able to deliver electrical stimulation to restore normal heart rhythm.

The ability to 3D print conductive polymer hydrogels with customized mechanical, electrical and adhesive properties opens up exciting prospects for a variety of implantable bioelectronic devices. These could include neural interfaces for brain-machine communication, gastric stimulators to treat digestive disorders and bladder sensors to manage incontinence.

Although progress in this area is promising, some challenges remain. Long-term biocompatibility must be ensured to avoid negative immune reactions. Scalability of the manufacturing process is also a challenge, as producing these devices on a commercial scale requires consistency and efficiency. Finally, regulatory hurdles must be overcome to meet the stringent safety and efficacy standards of health authorities.

More details can be found in the scientific paper “3D Printed Implantable Hydrogel Bioelectronics for Electrophysiological Monitoring and Electrical Modulation”.