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Atomic Force Microscope (AFM)-based Nanomanufacturing
# Innovative probe-based nanoscale patterning
Manufacturing on a nanometer scale has greatly advanced numerous fundamental research and industrial applications. AFM-based nanomanufacturing is able to produce arbitrary nanopatterns in a fast and low-cost manner. Combining with nanoimprint and soft lithography, this maskless technology has great potential in delivering customized and scalable 2D & 3D nanopatterns and nanodevices.
High-resolution nanomanufacturing with remains challenging. We created a probe-based nanomanufacturing process capable of fabricating customized nanopatterns down to sub-10 nm feature dimensions. With the integration of multiple energy types, including heat, electrical field, and mechanical vibration, a high-resolution and high-efficiency nanofabrication system has been experimentally demonstrated for patterning both insulating and conducting polymers. The new multiple energy-assisted process enabled a much higher manufacturing efficiency than typical single energy-assisted processes.
# Electric field-assisted probe-based fabrication processes
Electric field-assisted atomic force microscope (E-AFM) nanolithography is a novel polymer patterning technique that fabricate customized nanofeatures without the post-development procedure, which is a typical process in e-beam lithography. E-AFM uses a biased AFM tip with conductive coatings to make patterns with little probe-sample interaction, which thereby avoids the tip wear. However, the relatively large tip radius and large tip-sample separation limit its capacity to fabricate high-resolution nanopatterns.
we developed a contact mode electric-field-assisted AFM lithography process that generates high-resolution nanofeatures on polymer substrates using a soft probe. Constant force of 0.5-1 nN was applied to the AFM tip to secure the tip-film contact, in which localized electric breakdown took place inside the polymer film produced nanoholes and nanopatterns with adjustable feature dimensions. Nanostructures with feature widths down to ~16 nm were fabricated on a 15 nm-thick PMMA film, which was coated on a gold layer.
Atomic Force Microscope (AFM)-based Nanomanufacturing
# Electric field and mechanical vibration-assisted probe-based fabrication processes
The integration of electric field and mechanical vibration greatly increases the nanopatterning performances, which include high resolution (sub-10 nm feature width, ~6 nm), less debris as compared with mechanical force induced nanolithography, and higher patterning speed as compared with only either vibration or electric-field-assisted processes.
This approach is capable of fabricating nanopatterns on both insulating polymer (PMMA) and conducting polymer films (PEDOT:PSS).
3D Printing Process Innovations
#Clean and robust material extrusion process
The conventional material extrusion process has both quality issues and capability issues. The overheated polymer accumulations on the nozzles fall onto the parts during printing, significantly degrading product quality. The molten materials can easily accumulate on the nozzle and then become thermally degraded and form blobs on the printing nozzles, which eventually fall on the printed parts. Besides, the process has a narrow working window that can easily fail under certain scenarios, such as increased nozzle stand-off distances and reduced gravitational forces for in-space and unmanned manufacturing.
An electric field-assisted material extrusion (E-MEX) process was proposed to significantly enhance the printing quality and capabilities. By integrating an electric field with the material extrusion process, an electrostatic force was introduced between the printing nozzle and the platform to facilitate the printing process. The electrostatic force ensures a firm first-layer contact with the printing bed, even under increased stand-off distances and unconventional printing orientations. The extra force eliminates the necessity of the gravitational force during printing, warranting an in-space manufacturing scenario.
3D Printing Applications
#Pharmacy and Pharmaceutical Sciences (3D Printed Capsule Shells)
Individualized drug delivery improves drug efficacy and safety for patients. To implement individualized drug delivery, patient-specific tailored dosages produced on a small scale are needed. However, current pharmaceutical manufacturing is not suitable for personalized dosage forms. Although convenient to deliver various drugs, current gelatin capsules using animal collagen protein have many limitations, such as releasing drugs too fast and incompatibility with some diets. In contrast, 3D printed capsules have great potential to advance individualized treatments.
Our research demonstrated that both gastric and enteric capsules made with FDA-approved polymers via material extrusion processes are suitable for controlling and extending drug release. The release profiles of the capsules can be modified by making changes to the formulation.
Grants
1. NSF CMMI-2006127: "Multiple-Energy-Assisted Ultrasharp Probe-Based Nanomanufacturing for High-Resolution and High-Efficiency Nanopatterning", Jia Deng (PI), Changhong Ke (Co-PI), National Science Foundation, Division of Civil, Mechanical, and Manufacturing Innovation, $609,436, 07/01/2020 - 06/30/2024.
2. NSF CMMI-2442946: "CAREER: Probe-Based Hybrid Nanopatterning of Conductive Polymers", Jia Deng (PI), National Science Foundation, Division of Civil, Mechanical, and Manufacturing Innovation, $580,623, 08/01/2025 - 07/31/2030.
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