How The Brain Is Born: Flexible Implant Tracks Brain Growth In Real Time Without Interfering

Scientists have developed a super-thin, flexible implant that can be placed in the developing brains of tadpoles without causing damage. The device tracks the brain’s growth, adapting to its natural growth, and records neuron activity in real time, helping researchers better understand how the brain forms and how some neurological disorders arise from the earliest stages of life.

The development of the human brain (and that of other animals) is an extremely complex and delicate process, especially in the early stages of life. Understanding how the brain forms and how neurons begin to communicate could help scientists discover the causes of disorders such as autism, schizophrenia, and bipolar disorder, which often have their origins early in the embryonic stage.

However, studying this development in real time has always been a huge challenge, mainly because traditional research methods are invasive and can interfere with the brain’s own growth.

Recently, scientists at Harvard University took a major step towards overcoming this obstacle. They have created an extremely thin, soft and flexible bioelectronic device, similar to fabric or even tofu, that can be implanted in living embryos, such as tadpoles (amphibians in the early stages of life).

Tadpoles (baby frogs) were used in this study for several important reasons, especially useful for neuroscience and embryonic development research.

1- Visible brain development: Tadpoles have partially transparent bodies when they are in their early stages, which makes it easier to directly observe the development of the nervous system and to implant devices with precision.

2- Rapid growth: Tadpoles' brains develop rapidly, allowing scientists to follow many phases of brain growth in a shorter period of time than in other animals.

3- Simplicity of the nervous system: Compared to mammals, the nervous system of tadpoles is less complex, which makes it easier to study how the first neural activities arise and are organized.

4- Small size and easy to manipulate: They are small, easy to maintain in the laboratory and respond well to experimental manipulations, such as implants.

5- Lower ethical impact: Using tadpole embryos generally involves fewer ethical constraints than testing on more developed animals, such as mice or primates, especially at early stages of life.

These characteristics make tadpoles an ideal model for testing new technologies, such as this implant that tracks brain growth from the earliest stages, helping scientists better understand how the human brain can also develop and where disorders such as autism or schizophrenia may arise.

This implant is like a super-thin, soft network made of tiny wires called microelectrodes. These wires act as tiny sensors that can “listen” to and record the electrical signals that neurons (brain cells) use to communicate.

Imagine a type of electronic fabric that can be placed inside the body without hurting or disturbing anything. It was specially designed to be as flexible as the brain itself, which in the early stages of life is very soft, almost like jelly.

Diagram showing how the electrode adapts during the development of the tadpole embryo's brain. Credit: Liu Lab / Harvard SEAS

During development, the brain begins as a flat layer and, over time, folds and grows in three dimensions, forming the different parts of the nervous system, such as the brain and spinal cord.

The great thing about this implant is that it can keep up with all these changes in shape; it folds, stretches and grows along with the brain tissue. In other words, it does not need to be removed or repositioned, because it adapts on its own to the transformations of the growing brain.

In addition, because it is made of an extremely delicate material that is compatible with the body, it does not cause inflammation, damage or interfere with the normal functioning of the developing brain.

This is very important because it allows scientists to study how the brain is developing without disrupting this natural process. It's like an "invisible window" that shows everything that's happening inside an embryo's head, without it noticing or suffering any negative effects.

This innovative device is made from a material called perfluoropolyether dimethacrylate, a type of polymer (special plastic) that is both strong and soft enough to bend and stretch with brain tissue.

This allows scientists to track in real time, with millisecond precision, the electrical activity of individual neurons during all stages of brain development. For the first time, it has been possible to observe how nerve signals arise and organize themselves in a brain that is still forming, without having to interrupt or damage this process.

Diagram showing the electrode recording the electrical activity of different neurons from birth.

In addition to recording brain activity, the implant can also stimulate neurons through small electrical currents. This opens the door to studies on how the brain regenerates and responds to stimuli during growth, and may even help understand how to treat or prevent neurological disorders in the future.

The idea is that, in the long term, this technology will allow us to monitor and perhaps even positively intervene in human brain development at very early stages.

READ MORE:

Brain implantation of soft bioelectronics via embryonic development

Hao Sheng, Ren Liu, Qiang Li, Zuwan Lin, Yichun He, Thomas S. Blum, Hao Zhao, Xin Tang, Wenbo Wang, Lishuai Jin, Zheliang Wang, Emma Hsiao, Paul Le Floch, Hao Shen, Ariel J. Lee, Rachael Alice Jonas-Closs, James Briggs, Siyi Liu, Daniel Solomon, Xiao Wang, Jessica L. Whited, Nanshu Lu, and Jia Liu 

Nature. 11 June 2025

https://doi.org/10.1038/s41586-025-09106-8

Abstract:

Developing bioelectronics capable of stably tracking brain-wide, single-cell, millisecond-resolved neural activity in the developing brain is critical for advancing neuroscience and understanding neurodevelopmental disorders. During development, the three-dimensional structure of the vertebrate brain arises from a two-dimensional neural plate1,2. These large morphological changes have previously posed a challenge for implantable bioelectronics to reliably track neural activity throughout brain development3,4,5,6,7,8,9. Here we introduce a tissue-level-soft, submicrometre-thick mesh microelectrode array that integrates into the embryonic neural plate by leveraging the tissue’s natural two-dimensional-to-three-dimensional reconfiguration. As organogenesis progresses, the mesh deforms, stretches and distributes throughout the brain, seamlessly integrating with neural tissue. Immunostaining, gene expression analysis and behavioural testing confirm no adverse effects on brain development or function. This embedded electrode array enables long-term, stable mapping of how single-neuron activity and population dynamics emerge and evolve during brain development. In axolotl models, it not only records neural electrical activity during regeneration but also modulates the process through electrical stimulation.