Project Objectives:

grubo is a set of soft pneumatic actuators compatible with the Lego Technic system. The kit consists of expandable silicone air chambers, Lego-compatible connector pieces, and tubing and syringes to inflate the air chambers. Using the grubo pieces, builders can expand the functionality of their Lego creations with soft pneumatic actuation.

Creative Design Opportunities:

We imagine that the findings from our project can be implemented in various contexts, they are:

Within an educational institution: We imagine this set to be useful in providing a low barrier of entry for students in elementary schools to introduce students to pneumatic actuation through a method of creative play with which they are already familiar. Students may be given kits with Lego and grubo components, as well as instructions to guide students through projects that take advantage of the pneumatic actuation. This could also be implemented within other educational facilities like children’s museums, where interaction and collaborative play is encouraged.

A Lego Technic Set Add-on: A second potential avenue is to productize the kit. This concept is similar to existing Lego expansion kits that can add, for example, motorized functionality to already existing kits as well as new creations. In addition to being included in add-on kits, grubo components could also be incorporated into novel Lego sets, using the soft actuators to meet a specific designed end. We imagine this could interest established Lego fans.

grubo in Sculpture: The movement of the silicone components could also be used for biomimetic, sculptural ends . We named this project, somewhat facetiously, as grubo: a portmanteau of the words “grub” and “Lego,” because of the parts’ movement evoking images of larvae. Artists could employ these more complex versions of these connectors in artistic works to create dynamic, lifelike movements.

Outcomes:

Over the course of this project we developed a proof of concept for a kit of soft, inflatable, Lego-compatible components. While we only produced one one type of inflatable (one that bends when inflated) and one type of Lego connector (a 5-unit long male-male connector), we created parts that lay a clear groundwork for a whole line of similar pieces. The novel components also add new functionality to a Lego kit of parts, adding flexible, pneumatic actuation Technic-style builds.

We also developed a method for producing silicone inflatables with geometrically complex inner cavities. By making paraffin wax internal negatives and then melting them out of the cured silicone parts, we were able to produce monolithic silicone parts with internal cavities too large to remove rigid negatives from.

While we regard this project as an overall success, we have left notable room for improvement. By using a single, round connection point, the silicone parts can rotate around the air nozzles without much user control. Given the non-rotationally-symmetric nature of the silicone parts, this results in Lego builds that could be challenging to keep in a consistent state. Furthermore, the bistable connector nozzle is significantly narrower than the mouth of the plastic nozzles, a design choice that increases stability of the connection, but makes it challenging to easily mount the silicone pieces onto the plastic nozzles. This would likely prove a particular challenge for children, a target demographic of these toys. Additionally, we put not thought into how the syringes interact with the Lego system, so the syringes feel very unintegrated into the wider kit. Lastly, given the narrow range of parts we developed, the system lacks flexibility. Future iterations of this project would benefit from prioritizing solutions to these issues.

Citations:

While we looked at a lot of resources developing this project, we took primary inspiration from the following three:

1. Chao Zhang, Pingan Zhu, Yangqiao Lin, Zhongdong Jiao, Jun Zou. “Modular Soft Robotics: Modular Units, Connection Mechanisms, and Applications.” Advanced Intelligent Systems, Volume 2, Issue 6, page 1900166. 2020. doi: 10.1002/aisy.201900166.
   This paper presents a number of methods for creating modular soft robots. We found the high-level design specifications of our bistable connector from this paper.
2. Jun-Young Lee, Jaemin Eom, Woo-Young Choi, Kyu-Jin Cho. “Soft LEGO: Bottom-Up Design Platform for Soft Robotics.” 2018 IEEE/RSJ International Conference on Intelligent Robotics and Systems, Madrid, Spain, pages 7513-7520. 2018. doi: 10.1109/IROS.2018.8593546.
   A primary conceptual inspiration for our project. This paper presents another Lego-compatible inflatable soft actuator. These parts are compatible with the bricks rather than the Technic elements, and we through there was room to do more with the concept than was being done in this paper.
3. Golan Levin, Shawn Sims. Free Universal Construction Toy. 2012. url: http://fffff.at/free-universal-construction-kit/.
   The Free Universal Construction kit was another conceptual inspiration for our project. Similar to the previous citation, this work presents a kit of parts that can expand the functionality of the Lego (and other branded) building systems.
4. X. Lu, W. Xu, X. Li. “A Soft Robotic Tongue–Mechatronic Design and Surface Reconstruction.” IEEE/ASME Transactions on Mechatronics, Volume 22, Issue 5, Pages 2102-2110. October 2017. doi: 10.1109/TMECH.2017.2748606.
   The Soft Robotic Tongue provided a primary inspiration for the inflatable component we produced. This paper presents inflatable actuators as part of the tongue that, when inflated, provide a bending motion along one plane. While the actuators in the cited paper are more complex than what we produced, the basic design was adapted for the purposes of our project.

Technical Documentation:

A folder containing zips of our CAD files can be found here.

Contributions:

Sebastian: I focused primarily on developing the inflatable components. I designed the 3D-printed molds. I also figured out how to make the meltable wax internal components, and poured most of the casts.

Elena: I designed the hard plastic piece, focusing on the rigid bistable nozzles and adjusting tolerances for Lego compatibility. I also experimented with the bistable connection necks to find the diameters that worked the best.

Together: Both of us worked together to develop the concept for the project and to carry out early balloon and silicone experiments. Towards the end, we both worked together to make edits/fill in gaps left by the other with regards to part manufacturing and documentation.

ABS Lego parts: Trial One

Our printed Lego parts are very close to working. The tolerances are almost correct, but are just barely too tight. We are considering changing our CAD tolerances slightly, but we are also considering moving forward with SLA printing rather than FDM in order to achieve a more consistent tolerance to match with the tight tolerances of Lego parts.

Bistable Connection Progress

We’re currently trying to make progress on the bistable connection mechanism for our silicone parts. We’ve designed a preliminary mold design for our prototype connection, but Sebastian’s printer broke again, so we are currently waiting on a print from the Ideate printers to cast and evaluate the functionality of this design.

The Lego/tube/silicone connector progress:

We have modeled three parts (to accommodate for the FDM printers we will be using in the early iterations) and sent the parts to print on Sebastian’s printer. The printer couldn’t handle the thin tubes well, so we will send it to the Stratasys in the hopes of getting better prints. We see this part being SLA printed for the more final parts.

The Silicone/Air Chamber Part Progress

We tried to cast a silicone mold of one of the air chamber concepts from our last post. The silicone cast successfully, and we were able to avoid the leaking that we encountered last time, but we encountered a new problem: an inability to pull the central bit out of the mold.

In order to address this issue and some issues unnecessary excess material, we updated the design of our molds.

We attempted to make a negative of the center piece and cast it in a soy wax that could be melted out after the silicone cured. This initial attempt at casting wax failed, as the wax seemed to adhere better to the mold than to itself, breaking in half when we tried to split the mold in half.

We are going to continue trying to work with the wax. A couple things we are intending to try: adding draft angles where they do not currently exist, checking for and patching all holes in the 3D print (some wax leaked into the inside of the 3d print), breaking the mold into more parts to decrease the contact surface area of any given mold piece to the wax. Another potential avenue to improve this casting might be to switch from soy wax to a harder beeswax or even a paraffin wax. The increased rigidity might make it easier to separate from the mold in one piece.

We also adapted our previous bending block to be at a smaller scale and are testing it out on Sebastian’s newly-fixed printer.

We now have the Moldstar 30 silicone, and we’re working on manufacturing the molds to produce these two inflatables. We’re trying to debug the issues with Sebastian’s printer to so we can use that for the project, but in the meantime, we’d also like to try printing at least one of these prototypes through the Ideate printer to get a sense for what the logistic overhead for that process would be.

We also attempted to create a mold by hand from plasticine and cardboard. All of the molds seemed to have issues with holes, the plasticine mold due to shoddy assembly and the printed molds because the prints partially failed and we missed some holes while attempting to patch them. We were able to remove the silicone cast from the plasticine mold, although we ended up with just a large block of silicone that had collected in the cup we put the plasticine mold in. The silicone in the printed molds made its way into the gaps between the layers and we were completely unable to remove these casts from their molds as a result.

Next Steps

1. Print the second model we have at a smaller scale in more parts. This could use either the School of Design’s printers or use ideate printers, while we wait for more PLA, which could solve this printer’s issues, to arrive for Sebastians printer.
2. Work on the silcone to lego connector

Our project explores the possibility of integrating a pneumatic system of parts to an existing framework of toys, in this case: Legos. This new system, presents the potential to teach those who may be unfamiliar with soft robotics with a lower barrier of entry to the field. The compatibility of the soft pneumatic parts to a game system like Legos, gives the opportunity to build new knowledge off of an existing foundation. The pneumatic parts themselves explore different silicone air chamber configurations, which can present an assortment of bending paths, thus teaching something about air flow and how rate of airflow changes the created form. Our users are those unfamiliar with the field of soft robotics and has the desire to create with Legos.

Experiment Steps:

Our experiment remains roughly the same as last class. We plan on utilizing the materials given to us by Garth to explore what next steps we can take. As of right now, our experiment involves using a syringe, using a connector to connect to plastic tubing, and then using a plastic barbed fitting to connect a balloon. This is primarily to test the connection and the ability to pass air effectively through the parts. From there we can then test whether the barbed fitting can serve as a driving constraint for future silicone/inflatable explorations. After inflation, we also plan to look into how we can utilize the inflation/deflation to create some interesting forms with the balloons or some other inflatable material.

Bill of Materials:

Relevant Technical Papers:

We found a literature review focusing specifically on modular soft robotics (1). A section of the paper surveys different approaches to connecting modular soft actuators, and we think this section will be valuable as we do our research. It outlines different forms of connections, notably a wide range of both soft and rigid mechanical connections, capable of holding actuated parts together while letting air or another fluid pass through without escaping.

Of these connectors presented, the bistable connector, which consists of a lip that flips inside-out when engaged with a rigid connector, seems particularly promising and possible to implement. This might be a strong contender for a mechanism to experiment with once this first experiment is completed and we can move on to more custom components for the soft actuators.

Works Cited:
1. Chao Zhang, Pingan Zhu, Yangqiao Lin, Zhongdong Jiao, Jun Zou. “Modular Soft Robotics: Modular Units, Connection Mechanisms, and Applications.” Advanced Intelligent Systems, Volume 2, Issue 6, page 1900166. 2020. doi: 10.1002/aisy.201900166.

As we previously mentioned, we are planning to work with a system of manual pumps and soft actuated parts connected through tubes to make the parts move. Before testing the viability of the modularity, we wanted to make sure the base of the system is viable. This will be through testing how effective the flexible hose and inflatable object connection is. For the first experiment, we will use the four parts listed out below (with a larger syringe) and connect the fourth part’s threaded end to a balloon. From this, we will evaluate performance primarily on how efficiently it allows inflation, and whether the threaded end can serve as a driving constraint for future silicone/inflatable explorations.

https://courses.ideate.cmu.edu/16-376/s2021/ref/text/resources/kit-visual-guide.html#pneumatics

From this link, we have determined four parts to be included in our bill of materials:

Based off of the reading, I have assigned the following changes to my initial proposal.

1. The incorporation of sensing and input to produce a physical change, this could be controlled through an air pump provided in the kit.
2. Compression with non-elastic bags could be used in the kit, they can behave like biceps to bend not only paper but even thin sheets of wood. There can be some exploration with plastic welding patterns using longer plastic strips. Another approach can be providing different airbag sizes that children can then be attached to strips of paper.

Lining Yao, Ryuma Niiyama, Jifei Ou, Sean Follmer, Clark Della Silva, and Hiroshi Ishii. PneUI: pneumatically actuated soft composite materials for shape changing interfaces. In Proceedings of the 26th annual ACM symposium on User interface software and technology, UIST ’13, 13–22. Association for Computing Machinery, 2013. doi:10.1145/2501988.2502037.

Earlier explorations of soft lego research and pneumatic interfaces within soft robotics literary search as well as design searches of how electronics/tech is taught to kids brought me to this concept.

I present the idea of a kit that introduces various types of inflatable textures that can be pneumatically actuated or activated through a hand pump. Through research done in class, it seems like the variance of the form of various inflatable soft robotics is dependent on folding patterns and air pressure. The kit can then include various methods of folding the material to get a different kind of movement and interaction. The kit’s contents can potentially be connected to a series of air-tubes that the user can then assemble/disassemble to explore different configurations for the kit’s contents. This can serve as an introduction through a subsection (inflatable/pneumatic) of soft robotics.

Sources:

Robotics:

J. Lee, J. Eom, W. Choi and K. Cho, “Soft LEGO: Bottom-Up Design Platform for Soft Robotics,” 2018 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), Madrid, Spain, 2018, pp. 7513-7520, doi: 10.1109/IROS.2018.8593546.

https://tangible.media.mit.edu/project/pneui/

Design:

https://www.dezeen.com/2017/06/06/stem-learning-kits-kids-combine-technology-play-dough-universe-tech-will-save-us-design/

https://www.dezeen.com/2018/07/18/saki-maruyamas-knotty-childrens-toy-royal-college-arts-graduate/

https://www.dezeen.com/2018/07/30/feeling-robot-cornell-university-texture-changing-skin-technology/

SplashDisplay is an interactive art piece on temporary display at Kawasaki City Museum. Created by a team of researchers and artists and headed by Yasushi Matoba, a Ph.D. candidiate for HCI at the University of Electro-Communicatuions, Japan.

This project utilizes projectile beads on the table to create a real time volumetric display system. When pressured air hits from the bottom of the table the balls fly up and are illuminated, the result is a three-dimensional light display combining the physical and digital interfaces.

The entire experience is quite technologically dependent. Under the table is a xy table attached to a speaker to push up the tiny balls. To detect movement, the setup is equipped with an IR camera, IR light, and projector to display light screens. When an object interacts with the display it is detected by the IR light and the display responds accordingly.

An avenue of interest to explore could be how currently the balls are confined to the area of the table because of the xy speaker area. The incorporation of the speaker could incorporate other means of interaction that may not necessitate the motor and movement system underneath, thus freeing the project up to a larger field of engagement and interaction.