Commercially available fused deposition modeling (FDM) printers have yet to bridge the gap between printing soft, flexible materials and printing hard, rigid materials. This work presents a custom printer solution, based on open-source hardware and software, which allows a user to print both flexible and rigid polymer materials. The materials printed include NinjaFlex, SemiFlex, acrylonitrile-butadiene-styrene (ABS), Nylon, and Polycarbonate. In order to print rigid materials, a custom, high-temperature heated bed was designed to act as a print stage. Additionally, high temperature extruders were included in the design to accommodate the printing requirements of both flexible and rigid filaments. Across 25 equally spaced points on the print plate, the maximum temperature difference between any two points on the heated bed was found to be ∼9°C for a target temperature of 170°C. With a uniform temperature profile across the plate, functional prints were achieved in each material. The print quality varied, dependent on material; however, the standard deviation of layer thicknesses and size measurements of the parts were comparable to those produced on a Zortrax M200 printer. After calibration and further process development, the custom printer will be integrated into the NEXUS system — a multiscale additive manufacturing instrument with integrated 3D printing and robotic assembly (NSF Award #1828355).

The objective of this paper is to demonstrate the flexure properties of ABS plastic in a 3D printed object as a process to enable embedded pressure sensing capabilities. Developing the potential for non-static 3D parts broadens the scope of the fused deposition modeling (FDM) process to include printing ‘smart’ objects that utilize intrinsic material properties to act as microphones, load sensors, accelerometers, etc. In order to demonstrate a strain-based pressure transducer, strain gauges were embedded either directly on top or in the middle of a flexible ABS diaphragm. Securing a strain gage directly on top of the diaphragm traced a reference pressure more closely than diaphragms with the strain gage embedded halfway into the diaphragm. To prevent temperature-related drift, an additional strain gage was suspended above the secured gage, inside the 3D printed cavity. The additional gage allowed for a half-bridge circuit in lieu of a quarter-bridge circuit, which minimized drift due to temperature change. The ABS diaphragm showed no significant signs of elastic hysteresis or nonlinear buckling. When sealed with 100% acetone, the diaphragm leaked ∼50x slower than as-printed sensors. After pressurizing and depressurizing the devices multiple times, they output pressure readouts that were consistent and repeatable for any given pressure within the operational range of 0 to 7psi. The repeatability of each of the final generation sensors indicates that ‘smart’ objects printed using an FDM process could be individually calibrated to make repeatable recordings. This work demonstrates a concept overlooked previous to now — FDM printed objects are not limited to static models, which lack dynamic motion of the part as an element of design. Altering FDM’s bottom-up process can allow for easily embedding sensing elements that result in printed objects which are functional on the mesoscale.

This paper presents the fabrication of nanochannels using glancing angle deposition (GLAD) with line seeds. GLAD is a bottom-up nanofabrication technique that creates nanometer-level features by the ballistic shadowing effect at oblique incident angles in physical vapor deposition (PVD) processes. GLAD exhibits the unique advantage to create 3D nanofeatures such as nanocolumns, helices, chevrons, and combinations, comparing to top-down nanonamufacturing techniques. Advanced seeding schemes allow GLAD to produce ordered nanostructure arrays. In this paper, we focus on studying the design rules of line seeds for GLAD, and the potential for creating nanochannels using GLAD nanoribbons grown from the line seeds. Unlike traditional one-dimensional (1D) point seeds, the cross-sectional profiles of line seeds have an important impact on the size and morphology of the nanoribbons. We demonstrated that line seeds with circular cross-sections and micrometer widths created from conventional photolithography can be used for creating ribbons with width less than 300 nm. The centimeter-long nanoribbons are used as nanotemplates for nanochannels. The process is compatible with various materials such as parylene C and silicon dioxide as the capping material, and rigid/flexible substrate choices for the nanochannels as well. The nanochannels created by GLAD with line seeds can potentially be used in nanofluidics, biological, and sensing applications.

To adhere an artificial retinal implant onto the epiretinal surface of the eye, our group has designed retinal microtacks. The microtacks were fabricated by first bonding titanium foil to a silicon wafer; the tacks were then machined using an ultra-high precision micromilling technique with a 150-μm end-mill. The versatility of the micromilling technique allowed a partially conical, tapered tip to be added to the Ti tack, which created a sharp point. The Ti tacks average overall length and width were measured to be within 1% and 6%, respectively, of the design. Additionally, the grip width, stop thickness, and the tip taper angle of the Ti tacks were within 3%, 9%, and 4%, respectively, of the design.

To adhere an artificial retinal implant onto the epiretinal surface of the eye, our group has designed retinal microtacks. The microtacks were fabricated using two different micromachining techniques: 1) deep reactive ion etching (DRIE) and 2) ultrahigh precision micromilling. The DRIE process consisted of machining a double-sided polished three-inch silicon wafer using ICP with the Bosch process. For the ultra-high precision micromilling technique, titanium foil was bonded to a silicon wafer and precision machined with a 150-μm end-mill using PMAC code interfaced to a machine motion controller. Due to fabrication limitations, the tip of the DRIE fabricated Si tack was chisel-shaped, whereas versatility of the micromilling technique allowed a partially conical, tapered tip to be added to the Ti tack, which created a sharper point. For the Si tacks, the average overall length and width were measured to be within 7% and 2%, respectively, of the design while the Ti tacks were found to be within 1% and 6%, respectively. Additionally, the grip width, stop thickness, and the tip taper angle of the Ti tacks were within 3%, 9%, and 4%, respectively, of the design.

This paper reports a numerical design analysis of electrostatically actuated micromembranes. We systematically compare membrane performance in terms of natural frequencies, pull-in voltage (the bias voltage at which the membrane contacts the base electrode) and the effects of variable leg lengths for a given membrane size. Some experimental data on membrane deflection profiles versus bias voltage is included along with some experimentally determined pull-in voltages. Polysilicon micromembranes were successfully fabricated using the low cost MUMPs process that limits the user to three structural layers. The devices are designed with an emphasis on the response of the membrane to applied DC bias voltage to allow for variable stiffening. Circular membranes with diameters ranging from 60 to 160 μm, suspended 2 μm over square back plates of side lengths varying from 60 to 140 μm are investigated for voltages up to 90 volts. Three-dimensional electromechanical finite element simulations have been performed. Pull-in voltage values from simulations compare favorably with the measured results. It was observed that, for maximum deflection of the membrane upon application of DC bias voltage, the optimal dimensions for back plate and top membrane should fall within the ranges 80–120 μm and 80–140 μm, respectively.