I. Core Research Summary

• Ultra-High-Precision Rapid Fabrication of Aerosol Master Molds

The minimum lateral linewidth is 10 μm, and the single-layer vertical thickness can be controlled down to 0.5 μm. Compared with conventional inkjet‑based molds, this technology achieves five times higher lateral precision and 32 times higher vertical resolution. A single mold can be reused multiple times, with the cost of a single mixed‑structure ink cartridge less than one cent. The entire molding and curing process takes under three hours, eliminating the need for custom photolithography mask fabrication.

• Free-form fabrication of multi-geometric three-dimensional microchannels

By employing layered additive manufacturing, it is possible to fabricate stepwise structures, continuous inclined surfaces, triangular cross‑sections, and serpentine hybrid microfluidic channels with a single click. The channel height can be linearly tuned by adjusting the number of printing layers, and fluorescence‑based fluidic assays demonstrate that channels of varying heights can stably generate stratified concentration gradients, making them well suited for multi‑factor biochemical screening.

• Selective Functional Modification of Flow Channel Fixed Points

Aerosol‑based precise positioning: at T‑junctions, one side is coated with a PVA hydrophilic layer, while the other remains unmodified; the fluid flows exclusively along the hydrophilic region, enabling passive, valve‑free directional flow and addressing the industry challenge of unable to achieve spatially selective modification in spin‑coating or dip‑coating processes.

• Compatible with multiple types of printing ink systems

Both silver and polyimide master‑mold inks can stably form via atomization, leaving no residual contaminants after mold release. The PVA‑hydrophilic‑modified ink enables partitioned deposition in a single step, allowing seamless switching among metal, polymer, and hydrophilic‑modified materials on a single system.

• Standardized Gradient Mixing Chip Verification

The T‑shaped splitter combined with a serpentine mixing structure can stably generate an eight‑level continuous fluorescence concentration gradient, while maintaining laminar flow without turbulence. It is well suited for parallel high‑throughput analysis of small‑molecule drugs and protein samples, with chip fluidic performance on par with that of photolithographic devices.

II. Core Operating Principle of Aerosol Spraying and Its Unique Process Advantages

(1) Complete microfluidic control to prepare two sets of process flows.

Process 1: Aerosol printing of the master mold + PDMS soft-lithography fabrication of the chip

• Ultrasonic/pneumatic atomization of silver/PI ink, with nitrogen as the carrier gas delivered to the nozzle; a coaxial sheath gas stream compresses the micro‑mist jet.
• CAD‑based digital path printing of microchannel raised master molds, followed by segmented low‑temperature curing to remove the solvent;
• PDMS prepolymer is poured to coat the mold and crosslinked/cured at 80°C.
• PDMS is peeled off to form recessed microchannels, followed by perforation and plasma bonding with a glass substrate to complete the chip.

Process 2: Site-specific functionalization of the microfluidic channel interior

• Complete the PDMS-encapsulated microfluidic chip;
• The aerosol nozzle extends into the channel, and CNC control ensures that PVA hydrophilic ink is printed only within the designated section.
• At room temperature and under dry conditions, the coating adheres firmly to the inner wall of the channel, achieving localized hydrophilic modification.

(II) Five Core Technological Advantages (Compared with Lithography, Inkjet, and Two-Photon 3D Printing)

• Ultra-high-resolution bidirectional molding in both horizontal and vertical directions

A single layer can be controlled with a lateral dimension of 10 μm and a vertical dimension of 0.5 μm, far surpassing conventional inkjet‑based molds (50 μm line width, 16 μm layer height), enabling the fabrication of finely patterned micron‑scale flow‑diverting and mixing microstructures that meet the requirements of cell‑level microfluidic chips.

• Low-cost, rapid prototyping and iteration

No custom photomask is required; new molds can be produced within hours after design modifications, with minimal consumable usage. The molds are reusable, significantly reducing R&D prototyping costs and lead times.

• 3D Staircase / Freeform Inclined Surface

Layer-by-layer additive manufacturing, with each successive layer’s print length progressively reduced, enables continuous sloped surfaces; multi‑layer segmentation can achieve stepped height differences, whereas conventional photolithography is limited to single‑plane, isometric channels.

• Channel-specific zone modification—unique ability

The nozzle can extend into a sealed microcavity, enabling the deposition of hydrophilic, conductive, and bioactive coatings exclusively on the target area; by contrast, immersion and spin coating result in uniform modification across the entire surface, making it impossible to achieve unidirectional or localized functionalization.

• Universal ink for multiple materials and a wide range of viscosities

Metal nanoparticles, polymeric resins, and water-soluble functional‑modified inks can all be atomized interchangeably, enabling a single system to handle both mold fabrication and channel functional modification—eliminating the need for multiple sets of equipment.

III. Five Core Technological Innovations of This Study

Innovation 1: A Complete Process for Aerosol-Printed Microfluidic Master Molds

Innovation: A Two-Step Layered Stacking–Controlled 3D Microchannel Fabrication Technology

Innovative 3-point aerosol modification process within the microcavity

Innovation: A 4‑pole, ultra‑low‑consumable, reusable master mold solution

Innovation: A 5-in-1 Platform Integrating Mold Manufacturing and Channel Functionalization

IV. Existing Process Challenges and Corresponding Solutions for Overcoming Them

Challenge 1: Conventional inkjet molds have poor resolution, making it impossible to fabricate fine channel structures.

Challenge 2: Photomask customization involves long lead times and high per‑mask tooling costs, making small‑batch R&D economically unviable.

Challenge 3: Conventional modification methods can only render the entire channel hydrophilic, failing to achieve spatially localized control over fluid flow direction.

Challenge 4: Conventional 3D-printed molds are rough, and the PDMS replica exhibits poor surface smoothness in the microchannels.

Challenge 5: Most additive‑manufacturing molds are single‑use, leading to substantial material waste during batch prototyping.

V. Future Diversified Industrial Application Scenarios

1. Microfluidic Prototype for High-Throughput Drug Screening in University Laboratories

2. Customized fabrication of cellular organ-on-a-chip devices

3. Clinical POCT Rapid Diagnostic Chip R&D Platform

4. Micro-detection chip for trace environmental pollutants

5. Electrochemical Micro-Sensing Integrated Microfluidics

Figure 1. Schematic of the device fabrication process: starting with mold printing, followed by soft lithography, and concluding with scanning electron microscopy (SEM) images of the printed molds. (A) The aerosol jet printer operates by atomizing ink and transporting it via a nitrogen carrier gas; the ink‑laden nitrogen is then injected into the print head and ejected through nozzles onto the substrate to form the mold. An internal nitrogen sheath surrounding the ink‑laden stream further focuses the deposition area, while a heated platen beneath the substrate modulates the ink’s wettability and adhesion on the surface. (B) After the mold has cured, PDMS (with an elastomer-to-curing agent ratio of 10:1) is cast and allowed to cure until fully hardened. (C) Once the PDMS has hardened, the substrate is peeled away from the mold, leaving channels within the PDMS, which are then cleaned and dried. (D) On the PDMS chip, inlet and outlet ports are punched out, after which the chip is washed and plasma‑bonded to a coverslip. (E) SEM image of a cross‑section of the silver mold printed on a PVA‑coated glass slide. (F) Top‑view SEM image of the silver mold shown in panel E. (G) SEM image of a cross‑section of a triangular silver mold design printed on a PVA‑coated glass slide, with the single printed line at the top of the mold approximately 10 μm wide. (H) Top‑view SEM image of the silver mold depicted in panel G. All images share a uniform scale bar.

Figure 2. (A) The mean fluorescence intensity of each well (mean ± standard deviation from two replicate experiments) illustrates the input mixing gradient of the fluorescent dye across all eight reservoirs. This gradient is generated by a mixing device—schematically depicted in (B)—which features two inlet ports for delivering the fluorescent dye and the buffer solution, respectively. Under a pressure of 1 bar, both solutions are pumped and continuously split at a T‑junction, thereby establishing a concentration gradient of the fluorescent solute within the serpentine channel segment. The resulting mixture is then directed into the individual wells for imaging. (C) Shows images of each well, clearly demonstrating the expected intensity gradient across the entire setup: the leftmost well contains only the fluorescent dye, while the rightmost well contains only the buffer solution.

Figure 3. (A) A channel with two steps was fabricated, and the light intensity at each step was measured. Four channels with steps of different dimensions were prepared, and fluorescent dye was injected into them. The figure compares the measured channel heights with the light intensities recorded by fluorescence microscopy, revealing a clear linear trend as expected. The schematic in the lower right is based on a “five‑ring” structural system: the first layer consists of five rings, with each ring deposited at an ink height of 0.5 μm, resulting in a total base‑layer height of 2.5 μm; the second layer also comprises five rings, but with shorter line segments, forming another 2.5‑μm‑high structure that, when combined with the base layer, yields a total height of 5 μm; a third layer is then superimposed in the same manner, creating three stacked steps, each with a height increment of 2.5 μm. (B) Shows printed images of molds with varying slopes. (C) The graph illustrates the changes in light intensity as fluorescent dye flows through an inclined channel. Because the channel width remains constant throughout, the variation in light intensity directly reflects the corresponding changes in channel height. This experimental design is similar to that in (A), but with fewer rings per step and closer spacing, thereby producing a more gradual height‑change profile.

Figure 4. The flow of fluorescent dye in an aqueous solution through a PVA-coated channel. The liquid enters via the inlet (at the top of the image) and splits at the T‑junction: all the liquid preferentially flows toward the side containing the PVA coating, with no droplets reaching the uncoated side.