With the continuous advancement of neuroscience and bioelectronics, the development of high-performance, miniaturized, and personalized neural interfaces has become a major research focus. Traditional fabrication techniques, however, are limited in terms of high precision, complex structural design, and material diversity, underscoring the urgent need for more flexible, precise, and efficient micro- and nanofabrication methods. Aerosol jet printing (AJP), as an emerging micro- and nanofabrication technology, is leveraging its unique advantages to progressively drive innovation in neural prosthetic devices.

This paper provides an in-depth overview of the applications, advantages, challenges, and future prospects of AJP technology in the design and fabrication of neural prostheses.

Principle of Aerosol Jet Printing (AJP)

Aerosol Jet Printing (AJP) is a non-contact micro- and nano-printing technique that uses an ultrasonic atomization device to convert conductive, biological, or functional materials into fine aerosol particles, which are then ejected through a nozzle onto a substrate surface to form high-precision micro- and nanostructures.

Compared with conventional screen printing and lithography, AJP offers the following advantages:

• High resolution (up to 10 microns)

• Direct printing is possible on flexible, soft substrates (such as elastomeric polymers and biocompatible materials).

• Complex manufacturing capabilities spanning multiple materials, layers, and structures

• Non-contact, low-temperature processing is conducive to the preservation and application of biomaterials.

The core processes of AJP include:

• Convert conductive powders or biomaterials into aerosol particles

• Generation of fine aerosols via ultrasonic nebulization

• Use a high-pressure gas stream (typically air or an inert gas) to spray the aerosol onto the substrate.

• Control jet parameters to achieve precise deposition at the micro- and nanoscale.

This process significantly enhances printing flexibility and precision, making it well suited for fabricating high-density, multilayer neural electrode arrays and microsensors.

Innovative Applications of AJP in Neural Prosthetics

01 Fabrication of High-Precision Neural Interfaces

The core requirement for neural interfaces is to achieve high-density, multipoint, and low-damage transmission of neural signals. AJP can precisely fabricate ultrafine conductive traces and microelectrode arrays, thereby meeting this requirement.

Fabrication of microelectrode arrays: AJP enables rapid printing of conductive traces and electrodes on flexible substrates, yielding densely packed, extensively distributed arrays that can be used for precise localization and stimulation of the brain, spinal cord, or nerve fibers.

Multimaterial integration: By combining conductive and insulating materials, multifunctional composite structures can be engineered to enhance electrode performance and reliability.

Personalized customization: Based on the patient’s specific anatomical characteristics, rapid personalized design is achieved, enhancing implant comfort and signal quality.

02 Development of Elastic and Soft Electronic Devices

The nervous system is an exceptionally soft and dynamically adaptable tissue, making it difficult for conventional rigid electronic devices to integrate with it. The ability of AJP to directly print on flexible substrates opens up new possibilities for the development of soft electronics.

Flexible sensors and microelectrodes: Neural electrodes with high flexibility and stretchability are fabricated by inkjet printing metal nanowires or carbon materials onto elastic substrates such as silicone rubber and thermoplastic polyurethane.

Bendable and stretchable neural puncture needles: enabling safer, more comfortable implantation while reducing trauma and immune rejection during insertion.

Repair and Regeneration: Design detachable, replaceable soft neural interfaces to extend device lifespan and enhance clinical treatment outcomes.

03 Precise Integration and Application of Biosensing Materials

AJP’s multi-material deposition capability enables the fabrication of micrometer-scale microstructures, which, when combined with a variety of biocompatible materials, can be used to develop multifunctional, real-time-monitoring neural prostheses.

Printing of biosensors: integrating enzymatic, electrochemical, and other sensing technologies to detect neurochemical signals, inflammatory responses, blood glucose levels, and other biomarkers, thereby enabling closed-loop control.

Synchronous monitoring of neural signals and physiological parameters: By employing inkjet-printed microelectrode arrays, high-precision multi-site, multi-channel acquisition of neural signals is achieved, thereby enhancing signal quality and stability.

Drug Release and Regulation: Jet-printed micro-porous structures loaded with therapeutic agents, in conjunction with sensing data, enable localized, targeted drug delivery to facilitate nerve repair.

04 Manufacturing of Complex Systems with Multi-Material and Multi-Level Structures

AJP enables complex designs involving multiple materials, layers, and structures, providing a versatile manufacturing platform for innovative neural prostheses.

Composite material stacking: flexibly layering conductive, insulating, and cushioning materials to create a multifunctional multilayer neural interface.

Microfluidic integration: Combines microfluidic technologies to provide miniaturized channels for drug delivery or fluid signaling.

Intelligent devices: smart neural prostheses that enable self-sensing and automatic regulation, such as intelligent prosthetic limbs and brain–machine interfaces.

Advantages of AJP in Neural Engineering

01 High Spatial Resolution and Precise Control

AJP nozzles are extremely small in size, enabling micron-level precision patterning and meeting the microscale spatial requirements of the neuronal microenvironment.

02 High flexibility, adaptable to complex shapes

It enables direct printing on curved, arcuate, and irregular surfaces, making it particularly well-suited for the complex geometries of human biological tissues and thereby enhancing implantation success rates and signal quality.

03 Multi-material, multifunctional integration

Supports the deposition of a wide range of conductive, insulating, and biocompatible materials, meeting the multifunctional integration requirements of neural devices and accelerating research and clinical translation.

Illustrated Guide

Figure 1. General principle of AJP technology. AJP employs a sheath gas to focus atomized microdroplets into a tightly collimated, non-contact jet. This enables printing at variable stand-off distances (1–5 mm), accommodates a wide viscosity range (0.001–1 Pa·s), and reduces nozzle clogging. The system is compatible with high-viscosity inks and flexible substrates, making it well suited for fabricating complex biocompatible structures on non-planar surfaces.

Figure 2. Schematic diagram of the aerosol jet printing process. The figure illustrates five main stages: (1) atomization—using ultrasonic or pneumatic atomizers to convert liquid ink into a fine mist; (2) transport—conveying the aerosol to the nozzle via a carrier gas; (3) collimation—aligning and stabilizing the aerosol flow; (4) pneumatic focusing—employing a sheath gas to surround and narrow the aerosol stream into a micron-scale beam; and (5) deposition—depositing the atomized material onto the substrate in a precisely defined pattern.

Figure 3. Example of the AJP printing process for neural probes. (A) Conceptual schematic depicting key brain regions in the mouse: the prefrontal cortex, motor cortex, caudate–putamen, and hippocampal CA2/CA3. (B) Sagittal brain section showing the 3D-printed probe shaft (red) penetrating the cortex, striatum, and hippocampus. (C) Schematic diagram of the AJP-based rapid 3D printing of metal nanoparticles for customizing neural probes and circuit wiring. (D) Image of a 32-channel probe during printing. (E) Schematic design of the probe, including wiring and connectors. (F) The final printed probe shown alongside a U.S. one-cent coin for scale.

Figure 4. Neural prosthetic leg. A lower-limb amputee wears a custom-made prosthetic limb equipped with sensory-feedback devices at the knee and ankle joints. An encoder in the prosthetic knee (A) measures the degree of flexion, while a sensor-equipped insole collects pressure data. The sensor outputs are transmitted to an external controller, which activates a stimulator connected to a multichannel electrode array implanted in the tibial portion of the sciatic nerve (B), with the neural interface positioned within the nerve bundle.

Advanced microfabrication technologies, particularly aerosol jet printing and micro- and nano-fabrication, hold tremendous promise for applications in neural interfaces and bioelectronic devices. These technologies enable the rapid fabrication of high-precision, personalized neural probes and sensors, enhancing the capabilities for neural signal acquisition, stimulation, and feedback. As a result, they provide a robust foundation for the clinical application of brain–machine interfaces, neural repair, and intelligent prosthetics. Looking ahead, the integration of multi-material systems and advances in biocompatibility research are expected to drive the development of neural electronic devices toward greater miniaturization, flexibility, and intelligence, thereby significantly improving therapeutic outcomes for neurological disorders and ushering personalized medicine into a new era.

Aerosol Jet Printing (AJP) technology demonstrates exceptional high precision and multi-material compatibility in the fabrication of neuroelectronic devices, enabling the efficient fabrication of micron-scale electrodes and microstructures. Its outstanding spatial resolution and flexible adaptability provide robust support for the innovative development of bioelectronic devices such as soft neural interfaces and brain–machine interfaces, thereby advancing neuroengineering toward greater intelligence and personalization.