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Applications and methods of robotic 3D printing

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Robotic 3D printing uses techniques such as embedded printing, rotational multimaterial extrusion, vision-controlled jetting, and printable hydraulics to fabricate robots with integrated actuation, sensing, and structural components. These methods produce functional systems including soft grippers, crawling hexapods, shock-absorbing skins, and biomimetic actuators for surgical, assistive, and environmental applications.

Fabrication techniques in robotic 3D printing

Multimaterial jetting and printable hydraulics

Printable hydraulics utilizes an inkjet printer to deposit droplets of material measuring 20 to 30 microns in diameter, which is less than half the width of a human hair [1]. The fabrication process proceeds layer by layer from the bottom up, depositing distinct materials across separate regions and exposing each layer to high-intensity ultraviolet light to solidify all components except the liquid phases [2]. By configuring eight print heads to deposit diverse materials adjacent to one another simultaneously, the printing system achieves fine control over material placement and prints pre-filled fluidic channels directly [3].

Another jetting method is the programmable viscoelastic material technique, which enables engineers to program exact levels of stiffness and elasticity for every section of a printed object [4]. Using standard additive hardware, solid materials, liquids, and flexible rubber-like TangoBlack+ are combined in a single print operation to fabricate both structural bodies and protective skins [5].

Contactless vision-controlled jetting

Vision-controlled jetting provides an automated fabrication technique that monitors the print surface without relying on mechanical scrapers or rollers [6]. The system incorporates four high-frame-rate cameras and two lasers that rapidly and continuously scan the printing area [6]. An integrated computer vision pipeline converts scan data into a high-resolution depth map in less than a second, compares the depth map to the computer-aided design model of the part, and adjusts the resin output of individual nozzles to keep the part on target [7].

Because this process operates without mechanical contact, it successfully prints slow-curing thiol-based materials that would otherwise be smeared by physical smoothing components [8]. To form internal cavities and fluid networks, the platform deposits wax below structural elements as a support medium, which is subsequently melted and drained through heating to leave open channels throughout the object [9].

Rotational multimaterial printing and embedded sensing

Rotational multimaterial printing employs a dual-material nozzle that prints filaments featuring a flexible outer shell surrounding a removable inner gel [10]. Filaments are produced with a polyurethane outer shell and an inner channel composed of poloxamer, a polymer commonly found in hair gels [11]. Once the outer shell solidifies, the inner poloxamer gel is washed away to yield hollow tubular channels that bend in programmed directions upon pneumatic pressurization [12].

To integrate sensory functions directly into soft systems, embedded printing techniques deposit organic ionic liquid conductive inks within elastomeric matrices [13]. For multi-property actuators, voxel-level computational workflows break designs into millions of three-dimensional voxels that can each receive different materials [14]. Ray-tracing computer graphics simulations evaluate light interaction across voxel arrangements [15]. Drop-on-demand printers then fire 30-micron droplets from print heads with hundreds of individually controlled nozzles [16][17], depositing near-transparent rigid materials, flexible hinge polymers, and magnetic nanoparticle polymers into exact voxel coordinates [18].

Applications of 3D-printed robotic systems

Soft grippers and assistive devices

Embedded printing produces multifunctional soft grippers composed of three soft fingers capable of measuring inflation pressure, curvature, light and deep contact touch, and temperature [19]. Vision-controlled jetting has produced functional, tendon-driven robotic hands featuring 19 independently actuatable tendons, soft fingers with sensor pads, and rigid load-bearing bones [20].

Rotational multimaterial printing has demonstrated complex robotic components, including continuous flower-patterned actuators and five-digit handles equipped with bending knuckles [21]. Accessible printable robotics platforms have generated specialized designs such as the origami-inspired SEG Segway robot and pinching mechanisms designed to assist individuals using crutches or wheelchairs [22]. Multimaterial inkjet processes have also produced fluid-actuated rubber hands that mount onto existing commercial research robots [23].

Autonomous locomotion and high-resilience robotics

Simultaneous multi-material printing allows dynamic crawling robots to be produced in a single step with minimal post-print assembly [23]. Six-legged crawling hexapods have been fabricated with 12 hydraulic pumps embedded within their bodies [23], propelled by internal bellows that translate fluid pressure into mechanical force [24]. Vision-controlled jetting has fabricated six-legged walking robots that sense and grasp objects by integrating airtight interfaces between soft and rigid materials alongside internal channel systems [25].

For impact resistance, bouncing cube robots outfitted with programmable viscoelastic skins absorb substantial mechanical energy, transferring only 1/250 of ground collision energy [26]. These shock-absorbing skins improve landing precision nearly fourfold, offering potential lifespan extensions for delivery drones [27]. Furthermore, printable hydraulic robots can be rapidly fabricated with fewer electronic components, offering functional solutions for disaster relief operations in radioactive nuclear sites that disable conventional electronics [28].

Biomimetic actuators and shape-morphing mechanisms

Voxel-optimized printing enables magnetic biomimetic actuators, including artificial floating water lilies whose petals and hinges fold in response to magnetic fields transmitted through conductive fluids [29]. In marine applications, actuator arrays can be deployed across underwater robot skins to mimic shark skin denticles, deforming collectively to reduce hydrodynamic drag for faster and quieter swimming [30].

Key facts

  • Printable hydraulics uses an inkjet printer to deposit 20-to-30-micron droplets across eight print heads, using ultraviolet light to solidify photopolymers while leaving liquids uncured [1][2][3].
  • Vision-controlled jetting uses four high-frame-rate cameras and two lasers to generate depth maps in under a second and adjust resin delivery across 16,000 nozzles [6][7].
  • Contactless vision jetting processes slow-curing thiol-based polymers and uses sacrificial wax support to fabricate airtight walking robots with internal channels [8][9][25].
  • Rotational multimaterial printing extrudes filaments with polyurethane shells and removable poloxamer gel cores that wash away to leave hollow pneumatic channels [10][11][12].
  • Embedded 3D printing deposits organic ionic liquid inks inside elastomer matrices to measure inflation pressure, curvature, contact, and temperature in soft grippers [13][19].
  • Programmable viscoelastic materials allow regional programming of elasticity and stiffness, producing skins that absorb 249/250 of collision energy and improve landing precision fourfold [4][26][27].
  • Voxel optimization uses ray-tracing and drop-on-demand printing of 30-micron droplets to arrange rigid, flexible, and magnetically responsive polymers [14][15][16][17][18].
  • Demonstrated systems include 19-tendon hands [20], 12-pump crawling hexapods [23], assistive gripping tools [22], nuclear disaster-relief crawlers [28], and shark-inspired drag-reducing skins [30].

Sources

  • First-ever 3-D printed robots made of both solids and liquids news.mit.edu

    • [1]

      With “printable hydraulics,” an inkjet printer deposits individual droplets of material that are each 20 to 30 microns in diameter, or less than half the width of a human hair.

    • [2]

      For each layer, the printer deposits different materials in different parts, and then uses high-intensity UV light to solidify all of the materials (minus, of course, the liquids).

    • [3]

      Inkjet printing lets us have eight different print-heads deposit different materials adjacent to one another, all at the same time

    • [23]

      To demonstrate the concept, researchers 3-D printed a tiny six-legged robot that can crawl via 12 hydraulic pumps embedded within its body. They also 3-D printed robotic parts that can be used on existing platforms, such as a soft rubber hand for the Baxter research robot.

    • [24]

      Among the robot’s key parts are several set of “bellows” that are 3-D printed directly into its body. To propel the robot, the bellows uses fluid pressure that is then translated into a mechanical force.

    • [28]

      MacCurdy envisions many potential applications, including disaster relief in dangerous environments. Many nuclear sites, for example, need to be remediated to reduce their radiation levels.

  • 3-D-printed robots with shock-absorbing skins news.mit.edu

    • [4]

      The team’s “programmable viscoelastic material” (PVM) technique allows users to program every single part of a 3D-printed object to the exact levels of stiffness and elasticity they want, depending on the task they need for it.

    • [5]

      Using a standard 3-D printer, the team used a solid, a liquid, and a flexible rubber-like material called TangoBlack+ to print both the cube and its skins.

    • [26]

      For example, after 3-D printing a cube robot that moves by bouncing, the researchers outfitted it with shock-absorbing “skins” that use only 1/250 the amount of energy it transfers to the ground.

    • [27]

      The skins also allow the robot to land nearly four times more precisely, suggesting that similar shock absorbers could be used to help extend the lifespan of delivery drones like the ones being developed by Amazon and Google.

  • This 3D printer can watch itself fabricate objects | MIT CSAIL www.csail.mit.edu

    • [6]

      They developed a technique, known as vision-controlled jetting, which utilizes four high-frame-rate cameras and two lasers that rapidly and continuously scan the print surface.

    • [7]

      The computer vision system converts the image into a high-resolution depth map, a computation that takes less than a second to perform. It compares the depth map to the CAD (computer-aided design) model of the part being fabricated, and adjusts the amount of resin being deposited

    • [8]

      The researchers used the system to print with thiol-based materials, which are slower-curing than the traditional acrylic materials used in 3D printing.

    • [9]

      wax, which is used as a support material to create cavities or intricate networks of channels inside an object. The wax is printed below the structure as the device is fabricated. After it is complete, the object is heated so the wax melts and drains out, leaving open channels throughout the object.

    • [20]

      For one, they produced a functional, tendon-driven robotic hand that has 19 independently actuatable tendons, soft fingers with sensor pads, and rigid, load-bearing bones.

    • [25]

      “We also produced a six-legged walking robot that can sense objects and grasp them, which was possible due to the system’s ability to create airtight interfaces of soft and rigid materials, as well as complex channels inside the structure,” says Buchner.

  • 3D Printing Soft Robots seas.harvard.edu

    • [10]

      The technique employs rotational multimaterial 3D printing, in which a dual-material nozzle prints filaments with a flexible outer shell and removable inner gel.

    • [11]

      Using this general approach, the researchers created filaments made out of a polyurethane outer shell, and an inner channel made out of a polymer commonly found in hair gels, called a poloxamer.

    • [12]

      Once the outer shell solidified, the researchers then washed away the hair gel-like inner channel.

    • [21]

      They demonstrated their new technique by spiral-printing a flower pattern in one continuous, mazelike path. They also printed a five-digit handle complete with “knuckles” that bend.

  • Novel 3D printing method embeds sensing capabilities within robotic actuators seas.harvard.edu

    • [13]

      To address this challenge, the researchers developed an organic ionic liquid-based conductive ink that can be 3D printed within the soft elastomer matrices that comprise most soft robots.

    • [19]

      To test the sensors, the team printed a soft robotic gripper comprised of three soft fingers or actuators. The researchers tested the gripper’s ability to sense inflation pressure, curvature, contact, and temperature.

  • Automated system generates robotic parts for novel tasks | MIT CSAIL www.csail.mit.edu

    • [14]

      Software first breaks down the actuator design into millions of three-dimensional pixels, or “voxels,” that can each be filled with any of the materials.

    • [15]

      To compute the actuator’s appearances at each iteration, the researchers adopted a computer graphics technique called “ray-tracing,” which simulates the path of light interacting with objects.

    • [16]

      To fabricate the actuators, the researchers built a custom 3-D printer that uses a technique called “drop-on-demand.” Tubs of the three materials are connected to print heads with hundreds of nozzles that can be individually controlled.

    • [17]

      The printer fires a 30-micron-sized droplet of the designated material into its respective voxel location. Once the droplet lands on the substrate, it’s solidified.

    • [18]

      In the end, they produced a near-transparent rigid material, an opaque flexible material used as a hinge, and a brown nanoparticle material that responds to a magnetic signal.

    • [29]

      The researchers also 3-D printed floating water lilies with petals equipped with arrays of actuators and hinges that fold up in response to magnetic fields run through conductive fluids.

    • [30]

      For instance, other researchers are designing underwater robotic skins with actuator arrays meant to mimic denticles on shark skin. Denticles collectively deform to decrease drag for faster, quieter swimming.

  • Printable Robots Featured on Science Nation | MIT CSAIL www.csail.mit.edu

    • [22]

      The team has already produced several printable robots, including SEG, an origami-inspired Segway robot, and a small robot that can pinch and grasp objects, which might prove useful to a person on crutches or someone in a wheelchair.