With the increasing convergence of life sciences and electrical engineering, bioelectronic technologies have gradually emerged as a key driver of innovation in medicine, research, and industry. In particular, in the fields of tissue engineering and organ-on-a-chip systems, the development of efficient, flexible, and customizable electrode interfaces has become one of the major research priorities.

Although conventional microelectronic manufacturing technologies are well established, they still face numerous limitations when it comes to fabricating complex geometries, multilayer structures, and flexible, reconfigurable electrode systems. To address these challenges, the research community has been actively exploring novel fabrication approaches that integrate 3D bioprinting with micro- and nanofabrication techniques, thereby enabling bio-inspired innovations in electronic interfaces.

Background

The advancement of tissue engineering is inseparable from high-performance bioelectronic interfaces. As a core device for recording and stimulating electrical signals in neural and cardiac tissues, multi-electrode arrays (MEAs) are increasingly demanded to be highly flexible, ultrathin, customizable, and highly precise.

However, conventional microfabrication techniques such as photolithography and chemical etching suffer from high equipment costs, complex process flows, limited flexibility, and difficulty in meeting the demands of intricate 3D structures. These limitations restrict their application in in vivo studies and in the simulation of complex tissues.

Therefore, researchers have proposed employing aerosol jet printing (AJP) in conjunction with 3D bioprinting to revolutionize the fabrication of MEAs, enabling rapid, convenient, and personalized customization while supporting a wide range of materials and complex architectures.

Advantages and Breakthroughs of AJP Technology

01 High Flexibility and High Resolution: Aerosol Jet Printing (AJP) enables the precise deposition of micrometer-scale patterns on non-planar, flexible substrates, supporting the fabrication of complex 3D structures and surpassing the limitations of conventional planar microfabrication.

02 Material Diversity: Supports metals (such as gold and silver), conductive polymers, nanomaterials, and more, meeting multiple performance requirements including high conductivity and excellent biocompatibility.

03 Fast and low-cost: No need for expensive photolithography equipment or cleanroom conditions; simple operation, shortened manufacturing cycle, and reduced costs.

04 Scalability and Customizability: Enables personalized design, allowing for rapid adjustment of array layout or shape to meet specific research or clinical needs.

Design and Manufacturing Process

The research team first used computer-aided design (CAD) software to design multi-electrode arrays—such as circular and curved configurations—that meet the requirements of tissue engineering. Subsequently, the design files were converted into jetting paths, and metal ink was precisely deposited onto flexible thin films or 3D-printed scaffolds using an aerosol-based deposition system.

In terms of fabrication, a multi-layer jetting strategy is employed: conductive traces are printed first, followed by the deposition of electrodes and interconnects, and finally electrochemical modification is carried out to enhance conductivity and stimulation performance.

Meanwhile, to ensure the biocompatibility and stability of the electrode materials, polymer coating and electrode electroplating treatments were also implemented. The entire process enables rapid mold fabrication in a dust-free environment, supporting both large-scale and customized production.

I. Experimental Validation: Multifunctional, Multi-Material, and Multi-Structured MEAs

The research team conducted multiple experiments to evaluate the performance of AJP-fabricated MEAs in biomedical applications:

• Electrical performance testing: Evaluated using metrics such as electrical conductivity and impedance, the results demonstrate that metal electrodes fabricated via AJP exhibit outstanding conductivity and low noise, effectively meeting the requirements for neural and cardiac signal acquisition.

• Biocompatibility: The electrodes are coated with collagen (GelMA), allowing for the culture of muscle cells and neurons. The cells exhibit robust growth on the electrodes, maintain high viability, and show no significant cytotoxicity or adverse effects.

• Functional validation: Electrical stimulation was used to promote the directed growth of muscle cells, thereby influencing their structure and function. In addition, electrical signals from both neuronal and cardiomyocyte cultures were successfully recorded, confirming the recording capability of the electrodes.

• Applications in complex structures: By integrating flexible materials with AJP-fabricated multi-electrode systems on 3D-printed tissue models, electronic interfaces can be established for curved and bent geometries, making this approach highly suitable for future organ-on-a-chip platforms or organ mimetics.

II. Key Technology: Flexible and Diverse Electrode Design

The research team has developed a diverse array of electrode architectures, including curled, bent, grid-like, and dot-array configurations, to meet the needs of various tissue morphologies. Notably, in 3D-bioprinted catheters or scaffolds, AJP electrodes can be seamlessly integrated, thereby establishing a tightly coupled bioelectronic interface.

In addition, electrochemical deposition is employed to modify the electrode surface, enhancing its electrostimulatory performance, extending its service life, and ensuring long-term stability.

III. Practical Applications: From Cells to Tissues, from Basic Research to Clinical Translation

The core value of this technology lies in its broad application potential:

• Neuroscience research: enabling high-density, multipoint, and multilevel acquisition and stimulation of neural electrical signals, thereby providing technical support for brain–machine interfaces and neural network simulation.

• Cardiovascular tissue engineering: Establishing tissue models of cardiac muscle, blood vessels, and other cardiovascular tissues to enable electrical stimulation that promotes cell junction formation and functional synchronization, thereby providing a platform for research on cardiac diseases and drug screening.

• Musculoskeletal system: Develop organ-simulating models such as muscle and electrical stimulation catheters to advance research and development in muscle regeneration and rehabilitation technologies.

• Disease modeling and drug screening: Efficient generation of personalized, complex tissue models facilitates research on disease mechanisms and the development of new drugs.

Illustrated Guide

Figure 1. A) Schematic diagram of the microelectrode array platform for electrochemical stimulation and sensing. B) Schematic illustration of the aerosol jet printing process and the fabrication steps for the proposed MEA. C) Exploded view showing the MEA components. D) Proof-of-concept demonstrations of various applications using AJP-printed MEAs, including planar ex vivo MEA experiments, flexible MEA designs for DLP-printed tissue models, and electrostimulation and electrochemical sensing.

Figure 2. A) Schematic diagram of the design and dimensions of the microelectrode array (MEA) and its stimulation electrodes. B–D) Optical microscopy images showing the printing quality of the MEA and the stimulation electrodes. E–F) Scanning electron microscopy (SEM) images illustrating the surface morphology of the stimulation electrodes and the microelectrodes.

Figure 3. Electrochemical characterization of AJP-printed gold MEAs. A) Bode magnitude plots for the sensing electrode, the stimulating electrode, and the PEDOT/PSS-coated stimulating electrode. B) Bode phase plots for the different electrodes (sensing electrode, n = 21; stimulating electrode, n = 18; PEDOT/PSS-coated stimulating electrode, n = 4). C) Comparison of inter- and intra-sample relative standard deviations for pure gold electrode samples: inter-sample (sensing electrode on a singleMEA, n = 25) and intra-sample (sensing electrode across four MEAs, n = 100). D and E) Comparison of impedance magnitudes at 1 kHz and 1 Hz (sensing electrode, n = 21; stimulating electrode, n = 18; PEDOT/PSS-coated stimulating electrode, n = 4). F) Comparison of 1-kHz impedance magnitudes on day 0 and day 14 under standard cell-culture conditions (n = 23). G) Percentage increase in 1-kHz impedance for electrodes coated with GelMA, PDL, gelatin, and fibronectin, before and after coating (n = 4). H) Representative voltage traces of CICmax for a gold stimulating electrode compared with a PEDOT/PSS-coated stimulating electrode, with currents applied to the conventional gold and PEDOT/PSS electrodes of 575 μA and 2575 μA, respectively. I) Comparison of CICmax between the stimulating gold electrode and the PEDOT/PSS-coated stimulating electrode (n = 4). J) Stability of the PEDOT/PSS-coated stimulating electrode under 50-Hz biphasic pulses (n = 3). Error bars represent standard deviation. (ns, p > 0.05; *** p < 0.001; **** p < 0.0001).

Figure 4. Viability assay of bioprinted C2C12 cells encapsulated in 10% GelMA, evaluating the cytocompatibility of AJP-printed gold MEAs. A) Representative images captured using a 10× objective (scale bar, 100 μm). B) Bar graph showing the mean percentage of viable cells, with three samples cultured for 7 days and seven images acquired per sample. Error bars represent the standard deviation. (ns = not significant, p > 0.05).

Figure 5. Electrostimulation induces directional alignment of C2C12 cells. A) Representative fluorescence images of actin-stained C2C12 cells on the MEA under electrostimulation. The direction of electrostimulation is indicated by red double-headed arrows. White dashed lines denote the positions of the electrodes. B) Polar plot of the distribution of orientation angles as determined by image analysis in the stimulated group (n = 3, 30 sample images). C) Representative fluorescence images of actin-stained C2C12 cells on the MEA in the unstimulated condition. White dashed lines denote the positions of the electrodes. D) Polar plot of the distribution of orientation angles as determined by image analysis in the control group (n = 3, 30 sample images).

Figure 6. Extracellular recordings from AJP-printed MEAs. A) Filtered electrophysiological recordings from primary cortical neurons. B) Superimposed spike waveforms recorded from primary cortical neurons. C) Schematic representation of the AJP-printedMEA on a DLP-printed brain model. D) Mean waveform and standard deviation (shaded area) derived from (B). E) Filtered electrophysiological recordings from cultured HL-1 atrial cardiomyocytes. F) Superimposed spike waveforms recorded from HL-1 cells. G) Schematic representation of the AJP-printedMEA on a DLP-printed cardiac model. H) Mean waveform and standard deviation (shaded area) derived from (F).

Figure 7. Electrical stimulation of bio-3D-printed conduits. A) Fluorescent confocal images of activated (green) C2C12 cells growing within the conduit pores in the control group, and B) in the electrical stimulation group (magnification ×2.5). Insets show magnified views at ×10. Nuclei are counterstained with blue DAPI. Red arrows indicate the direction of electrical stimulation. Scale bar = 200 μm (n = 1). C) Digital photograph of a conformal MEA with printed hydrogel in the center. D) 3D rendered image of the hydrogel within the conformal MEA electrode system. The figure illustrates the direction of hydrogel expansion (scale bar = 1 cm).

Aerosol Jet Printing (AJP), when integrated with 3D bioprinting, offers an innovative approach that paves the way for next-generation tissue engineering and organ-on-a-chip technologies. By transcending the limitations of conventional microfabrication, AJP enables the rapid, flexible, customizable, and multifunctional fabrication of electronic interfaces, thereby establishing a robust foundation for the research and application of diverse tissues, including neural, cardiac, and muscular tissues.

In this paper, the research team successfully employed AJP to print a variety of key materials, including metallic conductive materials such as gold nanoparticles (AuNPs) and conductive polymers like PEDOT:PSS, thereby fabricating flexible, multifunctional multi-electrode arrays. They also used photosensitive insulating inks to print insulating layers, resulting in a complete multilayer electrode structure (T3, T4, T6). Furthermore, the study printed biocompatible conductive materials that exhibited excellent cell compatibility and successfully integrated 3D-bioprinted scaffolds and microfluidic channels for cell culture and electrical stimulation experiments, demonstrating the efficient integration of electronic interfaces with biological tissues.

In the future, as technology continues to advance and cross-disciplinary integration deepens, 3D bioelectronic manufacturing will emerge as a pivotal force in driving the advancement of life sciences and improving human health. We look forward to seeing an increasing array of AI-driven smart medical devices—and the transformative impact they will have on personalized, precision medicine—such as custom-designed neural interfaces, cardiac repair devices, and muscle-regeneration scaffolds. These innovative applications will leverage the versatility of AJP materials and the unparalleled flexibility of additive manufacturing, paving the way for a broad and promising future in precision, sustainable biomedical technologies.

Original article link: www.advhealthmat.de