The motivation behind the project lies in a persistent bottleneck in materials research. Solution-based printing, the family of techniques that includes inkjet, aerosol jet, gravure and screen printing, underpins modern work on flexible electronics, chemical sensors and printed diagnostics, all of which depend on depositing inks and functional fluids in exact locations on diverse substrates. Commercial tools such as the Fujifilm Dimatix Materials Printer DMP-2850 handle this task admirably, but their price places them beyond many academic groups. Meanwhile, the drive toward self-driving laboratories, where robots, liquid handlers and inline instruments work in concert to accelerate discovery, has exposed another cost barrier: automation platforms like the Opentrons OT-2 robot start at more than 15,000 dollars before a single experiment runs. The CRISP team set out to demonstrate that a frugal twin could be assembled from commodity hardware without sacrificing meaningful performance.

The engineering insight at the heart of the project is that a fused deposition modeling printer already contains nearly everything a liquid-dispensing robot needs. The Ender-3 provides robust three-axis motion control, a stepper motor for extrusion, an Arduino-class motherboard running Marlin firmware, and a mature G-code ecosystem. The researchers removed the hot end, heating block and filament spool holder, then mounted a syringe pump assembly on the printer’s upper frame. That pump is deliberately simple: a stainless-steel trapezoidal lead screw driven by the printer’s stock extruder stepper motor, a brass flanged nut riding on a 3D-printed gantry bracket, and two mounts that clamp a standard 20 milliliter Luer-lock syringe in place. When the motor turns, the threaded rod advances and the gantry bracket pushes the syringe plunger with kinematic regularity, converting rotational steps into volumetric dispensing.

Ink reaches the substrate through a length of fluorinated ethylene propylene tubing, roughly 75 centimeters long with a one-sixteenth-inch inner diameter, which press-fits into a nozzle made from a disposable polypropylene pipette tip. The choice of pipette tips as nozzles is a small piece of design genius: at 10 to 20 cents apiece, they are effectively consumables, and a clogged nozzle is solved by pulling the tip off and pressing on a new one rather than performing delicate surgery on an expensive printhead. The tips used in the demonstration have orifice diameters between roughly 0.35 and 0.50 millimeters, but because deposition is volumetric rather than nozzle-limited, the final droplet size on porous paper is governed mainly by the dispensed volume and how the fluid wicks into the fibers.

Because the syringe pump borrows the printer’s native extruder motor, it is programmed with ordinary G-code, the same command language hobbyists use to print plastic. This gives CRISP a surprisingly sophisticated feature set for its price: the number of programmed dispensing steps is limited only by how many G-code commands a user writes, which allows multi-step routines comparable to those of programmable laboratory pumps that cost several thousand dollars. For calibration, the team primed the tubing through the printer’s own interface, loaded a G-code file onto a microSD card, and let the machine execute its run from file. The comparison point is stark: a Chemyx 4000X programmable syringe pump runs about 4,400 dollars, while CRISP’s pumping hardware costs a fraction of that and integrates directly into a motion platform.

Validation began with a deliberately humble test fluid, a blue dye dissolved in water, chosen so that printing parameters could be optimized without the expense and opacity of metal nanoparticle inks. The team printed repeated five-by-five arrays of droplets on cardstock with dots spaced 20 millimeters apart and a programmed volume of 0.026 milliliters per drop. Quantitative image analysis using the open-source computer vision library OpenCV revealed a mean droplet circularity of 0.87 with a standard deviation of only 0.02, a coefficient of variation of 2.30 percent that indicates highly uniform droplet morphology. Positional accuracy proved equally respectable: the mean deviation between programmed and actual droplet centers was 0.65 millimeters, with a worst case of 1.25 millimeters, and the error distribution was random rather than systematic, confirming that the added syringe hardware introduces no mechanical drift into the printer’s kinematics.

Weighing the droplets provided an independent check on volumetric fidelity. Across five trials in which the system dispensed ten droplets into a tared dish, the average total mass was 265.9 milligrams, implying 26.59 microliters per drop against a kinematic prediction of 26.0 microliters, a percent error of just 2.3 with a coefficient of variation of 1.6 percent. Deposited on porous cardstock, the drops spread into hemispheres averaging about 4.6 millimeters in diameter, exactly matching volumetric expectations. The researchers note that the practical minimum droplet volume for this configuration is roughly 3 to 5 microliters, bounded by the stepper motor’s step resolution and fluid surface tension, though switching to a smaller syringe barrel would stretch that limit further by amplifying plunger travel per dispensed volume.

The team is candid about the platform’s boundaries. The nozzle holder as built maintains a physical gap of about 7 millimeters between tip and substrate, which is ideal for falling droplets but prevents the close tip-to-surface contact needed for a stable meniscus during continuous line printing; attempts to write continuous features with aqueous dye produced lines that thinned and broke. Paper remains the sweet spot because its fibrous structure absorbs liquid quickly, pinning particles before uneven drying can occur, whereas non-porous glass slides exhibited anomalous drying behavior related to well-known evaporative defects such as the coffee ring effect. The dead volume of the delivery tubing, roughly 1.5 milliliters, also matters when working with expensive reagents, and the authors recommend shorter, stiffer tubing and a heated print bed to tame environmental drying variability.

What makes CRISP more than a clever hack is its framing within the growing frugal-twin movement in chemistry and materials science, where low-cost replicas of commercial instruments are validated against their expensive counterparts. Structurally, the design resembles prior Ender-3 liquid-handling conversions, but it differs in relying entirely on stock printer hardware and 3D-printed brackets rather than an external syringe pump, keeping the added cost below 200 dollars. With results showing dispensing circularity of 98.2 percent and relative positional accuracy of 96.8 percent, the authors argue that stepper-driven commodity hardware offers sufficient repeatability for routine patterning tasks. Their ultimate goal is the deposition of metal nanoparticle inks for paper-based sensors, and with every CAD file, STL, G-code script and dataset published under open licenses on the Open Science Framework, CRISP invites laboratories worldwide to print droplets, not just plastic, for the price of a good dinner out.

Subject of Research: A low-cost 3D printer-based platform for precision solution printing on paper-based substrates

Article Title: CRISP: A 3D printer-based platform for precision solution printing on paper-based substrates

Article References: Lutfiyev, I., McCoy, S. A., Star, R., Giordano, A. N., Rist, B., Baldwin, L. A., & Rao, R. (2026). CRISP: A 3D printer-based platform for precision solution printing on paper-based substrates. HardwareX, 28, Article e00842. https://doi.org/10.1016/j.ohx.2026.e00842

Image Credits: AI Generated

DOI: 10.1016/j.ohx.2026.e00842

Keywords: CRISP, 3D printing, syringe pump, solution printing, paper-based substrates, Ender-3, open-source hardware, G-code, droplet deposition, frugal science, flexible sensors, HardwareX

The research, led by Chloé Melin of the École de Technologie Supérieure in Montreal and INSA-Lyon, together with Jean-Fabien Capsal, Ricardo Zednik, Angelo Pommella, Nicole Demarquette, and Jean-Marc Chenal, set out to answer a question that has lingered in the literature for years: does PLA actually help PVDF become a better piezoelectric material, or does it merely look like it does on a spectroscopy plot? The team attacked the problem from two processing directions at once. They melt-blended PVDF with PLA at weight ratios of 95/05 and 60/40 using a twin-screw extruder at 210 degrees Celsius, then compression-molded films and stretched them uniaxially at draw ratio 3 across a range of temperatures. In parallel, they prepared the same blend compositions as electrospun fibrous membranes using a semi-industrial twenty-needle unit, with both polymers dissolved together in a dimethyl sulfoxide and acetone mixture.

The central character in this story is the crystal structure of PVDF. The polymer can solidify into several distinct lattice forms, and they are not equal partners. The alpha phase, which forms readily when PVDF cools from the melt, is non-polar and piezoelectrically useless. The beta phase, in which polymer chains adopt an all-trans conformation, is highly polar and delivers the strongest piezoelectric response when the molecular dipoles are aligned by a high-voltage poling treatment. Converting alpha to beta is therefore the name of the game, and the two classic routes are uniaxial stretching of solid films and electrospinning, in which a jet of polymer solution is whipped by intense electric fields into nanometer- and micrometer-scale fibers, combining extreme elongational deformation with rapid solvent evaporation.

Morphology turned out to be the first fork in the road. In the melt-processed blends, scanning electron microscopy revealed that the 95/05 formulation produced a beaded, droplet-in-matrix structure, with discrete PLA domains dispersed in the PVDF, while the 60/40 blend formed a co-continuous architecture in which both polymers formed interpenetrating networks. Differential scanning calorimetry showed that adding PLA left the overall crystallinity of PVDF essentially unchanged at roughly 42 percent, before and after stretching, a consequence of the micrometric PLA domain size and the fact that PVDF crystallizes at a higher temperature than PLA. But the phase composition told a very different story. In the stretched 95/05 blend, the beta-phase fraction matched that of pure PVDF, whereas in the co-continuous 60/40 blend the beta fraction collapsed to 36 percent from the 86 percent achievable in well-processed samples, leaving the material dominated by the inert alpha phase.

The reason for that collapse is a lesson in mechanics. In a co-continuous blend, the macroscopic deformation applied during stretching is shared between the two continuous polymer networks, so the PVDF phase simply never sees enough local stress to drive the alpha-to-beta conformational transformation. Meanwhile, in the beaded 95/05 blend, the team observed cavitation, tiny voids opening at the PVDF-PLA interfaces during stretching, which relaxed local stresses and prevented the hoped-for enhancement of stress transfer to PVDF crystals. Earlier hypotheses in the literature had suggested that PLA could act as a stress concentrator, boosting beta formation through cavitation and heterogeneous deformation. This study’s data call that idea sharply into question: the beta fraction in the stretched blend was no better than in neat PVDF, and in some conditions worse.

Then came the electrical measurements, and the results were even more striking. After poling at 100 volts per micrometer for one hour in dielectric oil, the stretched 95/05 blend showed a piezoelectric coefficient d33 that was 34 to 45 percent lower than pure PVDF stretched under equivalent conditions, despite having a nearly identical beta-phase fraction. The culprit, the researchers showed, is dielectric mismatch. PVDF has a relative permittivity of about 10.8, while PLA’s is only 2.7. During poling, electric field lines preferentially route through the low-permittivity PLA inclusions and through the air-filled cavities left by stretching-induced voids, starving the surrounding PVDF matrix of the field it needs to rotate its dipoles. Finite element simulations in COMSOL Multiphysics, built on a representative volume element containing a PLA inclusion surrounded by an air ellipse, reproduced exactly this field concentration. When the team measured the piezoelectric response of pure PVDF poled at the reduced effective field of roughly 65 volts per micrometer, they obtained a d33 of about 6 piconewtons per coulomb, in close agreement with the blend’s measured value. The physics, in other words, checks out.

The co-continuous 60/40 blend, being overwhelmingly alpha phase, registered no measurable piezoelectric response at all, a d33 of zero. But the electrospinning results added their own twist. Pure electrospun PVDF membranes outperformed their stretched-film counterparts, delivering a d33 roughly 30 percent higher, thanks to about 29 percent greater overall beta-phase content and the superior chain alignment imparted by the enormous elongational forces inside the spinning jet. Interestingly, electrospinning also introduced a significant gamma-phase fraction, an intermediate polar conformation rarely seen in the stretched films, which the authors attribute to the rapid solvent evaporation and extreme deformation rates preserving the initially beta-nucleated chains only partially, letting them relax toward the gamma conformation rather than all the way to alpha.

Yet even electrospinning could not rescue the blend. The electrospun PVDF/PLA 95/05 membranes, despite achieving an electroactive phase fraction of about 86 percent, essentially identical to neat electrospun PVDF, showed a d33 of exactly zero after poling. The team points to a convergence of factors: the finely dispersed, highly elongated PLA domains formed during fiber formation disrupt the local electric field and hinder chain and lamellar orientation; the vastly increased interfacial area places PLA, which is stiffer than amorphous PVDF at the poling temperature, immediately adjacent to the crystal-amorphous interfaces where dipole switching initiates; and interfacial interactions locally stiffen the material, impeding the conformational kinks that must propagate through PVDF chains during poling. Raising the poling temperature triggered electrical breakdown, and lowering the field produced no effective dipole alignment, leaving the membranes piezoelectrically mute.

The study also challenges another widespread assumption. None of the electrospun membranes in this work showed measurable piezoelectric activity before an external poling step, even though the poling field used was nearly twice that of most previous studies reporting self-poled electrospun PVDF. The through-thickness dipole orientation required for a d33 response, the authors note, evidently does not emerge from the electrospinning process alone under these conditions, contradicting a body of literature that has treated self-poling as an intrinsic benefit of the technique.

The broader takeaway is a warning against a seductive shortcut. In the drive toward sustainable, flexible sensors and energy harvesters, blending PVDF with biobased PLA seems like an obvious win: PLA is renewable, biodegradable, stiff, and easy to process. But this work demonstrates that a high beta-phase fraction alone does not guarantee functional piezoelectricity. Electric field distribution, interfacial cavitation, domain size, chain mobility, and processing route all conspire to determine whether a material that looks piezoelectric under an infrared spectrometer actually produces a measurable voltage under stress. For engineers designing the next generation of self-powered wearables and structural health monitors, the message is clear: composition, morphology, and processing must be engineered together, and the role of PLA in enhancing the beta phase of PVDF, once considered promising, is now very much in doubt.

Subject of Research: Piezoelectric performance of PVDF/PLA polymer blends prepared by melt processing and electrospinning

Article Title: Piezoelectric properties of PVDF/PLA blends prepared by melt processing and electrospinning

Article References: Melin, C., Capsal, J.-F., Zednik, R., Pommella, A., Demarquette, N., & Chenal, J.-M. (2026). Piezoelectric properties of PVDF/PLA blends prepared by melt processing and electrospinning. Journal of Materials Science: Polymers, 1(1), Article 13. https://doi.org/10.1007/s44493-026-00010-9

Image Credits: AI Generated

DOI: 10.1007/s44493-026-00010-9

Keywords: PVDF, PLA, piezoelectricity, polymer blends, electrospinning, melt processing, beta phase, energy harvesting, flexible sensors, poling, crystallinity, dielectric permittivity