More Like this

1. Rapid Micromolding of Sub-100 µm Microfluidic Channels Using an 8K Stereolithographic Resin 3D Printer

   https://doi.org/10.3390/mi14081519  

   Vedhanayagam, Arpith; Golfetto, Michael; Ram, Jeffrey L.; Basu, Amar S. (August 2023, Micromachines)

   Nguyen, Nam-Trung; Munoz, Rodrigo Alejandro; Kalinke, Cristiane (Ed.)

   Engineering microfluidic devices relies on the ability to manufacture sub-100 micrometer fluidic channels. Conventional lithographic methods provide high resolution but require costly exposure tools and outsourcing of masks, which extends the turnaround time to several days. The desire to accelerate design/test cycles has motivated the rapid prototyping of microfluidic channels; however, many of these methods (e.g., laser cutters, craft cutters, fused deposition modeling) have feature sizes of several hundred microns or more. In this paper, we describe a 1-day process for fabricating sub-100 µm channels, leveraging a low-cost (USD 600) 8K digital light projection (DLP) 3D resin printer. The soft lithography process includes mold printing, post-treatment, and casting polydimethylsiloxane (PDMS) elastomer. The process can produce microchannels with 44 µm lateral resolution and 25 µm height, posts as small as 400 µm, aspect ratio up to 7, structures with varying z-height, integrated reservoirs for fluidic connections, and a built-in tray for casting. We discuss strategies to obtain reliable structures, prevent mold warpage, facilitate curing and removal of PDMS during molding, and recycle the solvents used in the process. To our knowledge, this is the first low-cost 3D printer that prints extruded structures that can mold sub-100 µm channels, providing a balance between resolution, turnaround time, and cost (~USD 5 for a 2 × 5 × 0.5 cm^3 chip) that will be attractive for many microfluidics labs. 

   more » « less
2. Area-Specific Positioning of Metallic Glass Nanowires on Si Substrate

   https://doi.org/10.1007/s41871-023-00205-6  

   Theeda, Sumanth; Kumar, Golden (July 2023, Nanomanufacturing and Metrology)

   Abstract This paper presents a novel technique to fabricate metallic nanowires in selective areas on a Si substrate. Thermoplastic drawing of viscous metallic glass from cavities etched in Si can produce metallic nanowires. The length and diameter of nanowires can be controlled by adjusting the drawing conditions without changing the Si mold. A thin metal shadow mask is stacked above the Si mold during thermoplastic drawing to fabricate the nanowires only in specific locations. The mask restricts the flow of metallic glass to predefined shapes on the mask, resulting in the formation of nanowires in selected areas on Si. An Al foil-based mask made by a benchtop vinyl cutter is used to demonstrate the proof-of-concept. Even a simple Al foil mask enables the positioning of metallic nanowires in selective areas as small as 200 µm on Si. The precision of the vinyl cutter limits the smallest dimensions of the patterned areas, which can be further improved by using laser-fabricated stencil masks. Results show that a single row of metallic glass nanowires can be patterned on Si using selective thermoplastic drawing. Controllable positioning of metallic nanowires on substrates can enable new applications and characterization techniques for nanostructures. 

   more » « less
3. Quantifying Patterned Features on Material Surfaces Created using Ga Ion Beam in FIB-SEM

   https://doi.org/10.1093/mam/ozaf001  

   Ghosh, Supriya; Mkhoyan, K Andre (March 2025, Microscopy and Microanalysis)

   Abstract We introduced and applied a set of parameters to quantify surface modifications and pattern resolutions made by a Ga ion beam in a focused ion beam instrument using two material systems, Si and SrTiO3. A combination of top-view scanning electron microscopy and cross-sectional scanning transmission electron microscopy imaging and energy-dispersive X-ray spectroscopy was used to study the structure, composition and measure dimensions of the patterned lines. The total ion dose was identified as the key parameter governing the line characteristics, which can be controlled by the degree of overlap among adjacent spots, beam dwell time at each spot, and number of beam passes for given beam size and current. At higher ion doses (>1015 ions/cm2), the Ga ions remove part of the material in the exposed area creating “channels” surrounded with amorphized regions, whereas at lower ion doses only amorphization occurs, creating “ridges” on the wafer surface. To pattern lines with similar sizes, an order of magnitude different ion doses was required for Si and SrTiO3 indicating strong material dependence. Quantification revealed that lines as fine as 10 nm can be reproducibly patterned and characterized on the surfaces of materials. 

   more » « less
4. An Implanted Magnetic Microfluidic Pump for In Vivo Bone Remodeling Applications

   https://doi.org/10.3390/mi11030300  

   Chen, Ziyu; Noh, Sunggi; Prisby, Rhonda D.; Lee, Jeong-Bong (March 2020, Micromachines)

   Modulations of fluid flow inside the bone intramedullary cavity has been found to stimulate bone cellular activities and augment bone growth. However, study on the efficacy of the fluid modulation has been limited to external syringe pumps connected to the bone intramedullary cavity through the skin tubing. We report an implantable magnetic microfluidic pump which is suitable for in vivo studies in rodents. A compact microfluidic pump (22 mm diameter, 5 mm in thickness) with NdFeB magnets was fabricated in polydimethylsiloxane (PDMS) using a set of stainless-steel molds. An external actuator with a larger magnet was used to wirelessly actuate the magnetic microfluidic pump. The characterization of the static pressure of the microfluidic pump as a function of size of magnets was assessed. The dynamic pressure of the pump was also characterized to estimate the output of the pump. The magnetic microfluidic pump was implanted into the back of a Fischer-344 rat and connected to the intramedullary cavity of the femur using a tube. On-demand wireless magnetic operation using an actuator outside of the body was found to induce pressure modulation of up to 38 mmHg inside the femoral intramedullary cavity of the rat. 

   more » « less
5. In vitro formation and extended culture of highly metabolically active and contractile tissues

   https://doi.org/10.1371/journal.pone.0293609  

   Bagdasarian, Isabella A.; Tonmoy, Thamidul Islam; Park, B. Hyle; Morgan, Joshua T. (November 2023, PLOS ONE)

   Jang, Hae Lin (Ed.)

   3D cell culture models have gained popularity in recent years as an alternative to animal and 2D cell culture models for pharmaceutical testing and disease modeling. Polydimethylsiloxane (PDMS) is a cost-effective and accessible molding material for 3D cultures; however, routine PDMS molding may not be appropriate for extended culture of contractile and metabolically active tissues. Failures can include loss of culture adhesion to the PDMS mold and limited culture surfaces for nutrient and waste diffusion. In this study, we evaluated PDMS molding materials and surface treatments for highly contractile and metabolically active 3D cell cultures. PDMS functionalized with polydopamine allowed for extended culture duration (14.8 ± 3.97 days) when compared to polyethylamine/glutaraldehyde functionalization (6.94 ± 2.74 days); Additionally, porous PDMS extended culture duration (16.7 ± 3.51 days) compared to smooth PDMS (6.33 ± 2.05 days) after treatment with TGF-β2 to increase culture contraction. Porous PDMS additionally allowed for large (13 mm tall × 8 mm diameter) constructs to be fed by diffusion through the mold, resulting in increased cell density (0.0210 ± 0.0049 mean nuclear fraction) compared to controls (0.0045 ± 0.0016 mean nuclear fraction). As a practical demonstration of the flexibility of porous PDMS, we engineered a vascular bioartificial muscle model (VBAM) and demonstrated extended culture of VBAMs anchored with porous PDMS posts. Using this model, we assessed the effect of feeding frequency on VBAM cellularity. Feeding 3×/week significantly increased nuclear fraction at multiple tissue depths relative to 2×/day. VBAM maturation was similarly improved in 3×/week feeding as measured by nuclear alignment (23.49° ± 3.644) and nuclear aspect ratio (2.274 ± 0.0643) relative to 2x/day (35.93° ± 2.942) and (1.371 ± 0.1127), respectively. The described techniques are designed to be simple and easy to implement with minimal training or expense, improving access to dense and/or metabolically active 3D cell culture models. 

   more » « less