3D Printed Stamp Enables Synthetic Muscles for Soft Robotics

A team of MIT researchers recently created the first synthetic muscle actuator that can flex in multiple directions. This study opens the door for more capable soft robots and other advanced medical breakthroughs. Here's how the team utilized a new 3D printing method, alongside specially made stamps, to grow synthetic muscles in the lab that can replicate the real thing.

Understanding Muscle Architecture and Movement

To understand why you can't just make a motor that does what a muscle does, you first need to look at how your body operates. When you move your hand, there is a lot more going on than just your muscles pulling in a single direction. Many multidirectional skeletal muscle fibers form intricate patterns and are mounted at angles to produce the exact motions of the human body.

Nature is incredibly efficient, and over billions of years of evolution, it has had the time to correct most errors in form and operations. That’s why engineers often look to nature to find inspiration for their designs. Recently, scientists have delved into growing skeletal muscle fibers.

Biohybrid Muscle Actuators and Their Limitations

These fibers contract when an electrical charge is applied. When the charge is removed, the muscles relax, allowing for repeatable operations. These soft biohybrid actuators provide energy efficiency, adaptability, and can be set up to fit nearly any form factor. However, they aren’t ideal for several reasons.

Challenges with Existing Synthetic Muscle Fabrication Methods

The current design of synthetic muscle actuators has a limited range of motion. In most applications, the synthetic muscle is connected between two points. This arrangement only allows the muscle to pull or relax along the mounted points.

Additionally, it's incredibly expensive to grow synthetic actuators. The current process of creating microscale topographical features in extracellular matrix hydrogels requires specialty equipment. Also, it’s a multi-step process that demands companies hire experts in the field of microfabrication.

Introducing STAMP: A New Fabrication Method for Synthetic Muscle Actuators

MIT researchers wanted to demonstrate a better method of creating synthetic muscles via a new stamping method. The study “Leveraging microtopography to pattern multi-oriented muscle actuators“¹ was published in the journal Biomaterials Science.

It highlights how the team was able to successfully utilize advanced 3D printing to create a more efficient and affordable method to grow artificial tissues that replicate the architectural complexity of real tissues like your iris muscles.

STAMP Methodology and 3D Printing Approach

As part of their research, the scientists created the STAMP (simple templating of actuators via micro-topographical patterning) fabrication method to provide reliable fabrication. Notably, the stamp was designed to fit into standard available 24-well plates. The team then utilized the high-precision 3D printing facilities in MIT.nano to create vertically aligned (90°) microgrooves into hydrogel casts.

Hydrogel Mat

A purpose-built hydrogel mat designed to encourage cell growth was created. The hydrogel is a soft material, but it can be set up with grooves or other designs to alter the cell growth. Notably, the design of the hydrogel mat closely resembles the researcher's previous work in which a similar material was used to grow a synthetic muscle and strengthen it.

Source – MIT

Anti-Stick Coating

Like an experienced baker, the engineers applied a nonstick coating to their stamps. This coating was made of a protein that supported high-fidelity patterning of micro-topographical cues without tearing. Interestingly, the team sterilized the stamping pad using UV systems before soaking the stamps for an hour in a 1% bovine serum albumin solution as a mold prohibitor.

Computational Modeling of Multi-Oriented Muscle Actuators

At the core of the experimentation was the team’s specialty built computer simulation. The team created the model to enable them to enhance their testing and experimentation attempts. This advanced simulation allowed the team to investigate how micro-topographical patterning impacted muscle alignment efficiency.

They were also able to spend time researching key details like fiber morphology and contractile function in both mouse and human myoblasts. From there, the team explored how cell size and groove size influenced muscle alignment and overall design. Impressively, the test results matched the computer simulation results, highlighting its usefulness and accuracy.

Testing the Iris-Inspired Multi-Directional Muscle Actuator

To test their theory, the engineers decided to take inspiration from a complex muscle in your eye. Your iris muscles allow it to adjust in multiple directions to accept the right amount of light. These muscles can move concentrically and radially, depending on what you're focusing on and other environmental conditions.

The engineers designed a mold that leveraged concentrically arranged circular muscle fibers that sat on radially positioned fibers. In your eyes, this complex design allows fine focusing and adjustments on the fly.

Notably, in this experiment, the artificial iris is fabricated with voluntary skeletal muscle cells, which differ from involuntary smooth muscle cells found in our body. Interestingly, the engineers noted that both mouse and human myoblasts seeded Optogenetic skeletal muscle fibers grown on a STAMPed iris substrate began fusing into fibers within 24 hours.

Let There Be Light

The muscle fibers were able to fully mature into a suitable replica of the iris, demonstrating how the new process can create complex designs when required. Unlike previous biorobotic muscle actuators, this new version was genetically modified to adjust when exposed to light.

This setup allows engineers to pinpoint which muscle to actuate exactly using light beams.  The choice to utilize spatially segregated regions of concentric and radial muscle fibers allowed engineers to control pupil constriction in concentric regions separately as well.

Results: Multi-Directional Actuation and Validation

The engineers conducted several experiments to showcase their creation and how it encourages muscle cells to grow and fuse into fibers. The synthetic muscle contracted in multiple directions when stimulated by light sources. Notably, the testing allowed the team to succeed in being the first to demonstrate a skeletal muscle-powered robot that generates multi-directional force.

The test results showed that the team successfully replicated the iris layout and capabilities. These test results show how the STAMP method enables the designing, creating, and testing of multidirectional synthetic muscle soft actuators with more efficiency.

Advantages of the STAMP Method for Muscle Engineering

The benefits of the synthetic muscle study will be felt across multiple industries. For one, the new method is far more accessible than the previous micro-fabrication strategies. The engineers noted that anyone could utilize a commercially available tabletop 3D printer to achieve similar results.

One-Step Method

The enhanced fabrication method allowed engineers to pattern microtopography of various sizes and configurations on the surface of hydrogels in a single step. Additionally, the STAMP can be cleaned using ultrasonic baths and reused multiple times, adding to its cost-effectiveness.

Precision

The system enables engineers to grow mouse and human skeletal muscle fibers without negatively impacting their maturation or function. Notably, the team stated it could grow muscles in nearly any pattern to accomplish complex motions.

Sustainable

Another major benefit of this type of actuator is that it has the potential to be biodegradable, just like humans. This approach will help to ensure people avoid a cell phone situation where landfills of the future are filled with outdated early robots that became obsolete as the technology improved.

Research Team and Funding Support

MIT engineers, led by Ritu Raman, authored the study. The paper was co-authored by Tamara Rossy, Laura Schwendeman, Sonika Kohli, Maheera Bawa, and Pavankumar Umashankar. Additional support for the project was provided by Roi Habba, Oren Tchaicheeyan, and Ayelet.

Financial grants for the project came from the U.S. National Science Foundation, the U.S. Office of Naval Research, the U.S. Army Research Office, and the U.S. National Institutes of Health.

Applications and Future Outlook for STAMP-Based Actuators

There are many applications for bioengineered muscle actuators, ranging from medicine to robotics. The STAMP method reduces costs and opens the door for large-scale production. As such, you can expect to hear a lot more about synthetic muscle-powered robots in the coming months.

Soft Robotics

Soft robotics is an emerging field that has endless possibilities. These robots differ from their counterparts in that they don’t utilize rigid structures. As such, they are well-suited for tasks that require a non-conforming design and the ability to alter access to intricate and hard-to-reach spots. Already, engineers are looking to design a fish that operates similarly to its natural counterparts rather than using propellers for propulsion.

Medical Treatments

The medical field would benefit greatly from this technology. Engineers predict the technology will be used to grow other types of biological tissues, such as neurons and heart cells. These lab-grown alternatives could be used to treat those suffering from neuromuscular disorders and more.

Additionally, the technique could help improve the ability of researchers to replicate human tissue for testing and drug development. The current methods of growing cells for drug treatment testing are slow and require a lot of time. This approach allows for fast and low-cost fabrication.

Estimated Timeline for Adoption

You can expect to see this technology begin to emerge commercially in the next 5-10 years, depending on market conditions. Currently, there’s a strong push to make robots more capable and efficient. Synthetic muscles allow this task and can be designed to strengthen with repeated use, just like your muscles.

This latest breakthrough opens the door for engineers at top robotics firms to experiment with making lighter, more efficient designs. The technology could replace most actuators, providing a reliable alternative that can strengthen performance with more use.

Disruptive Robotics in Action: Public Companies to Watch

While the MIT team’s biohybrid actuator remains in the research phase, its potential implications ripple across industries — particularly soft robotics, autonomous systems, and biomedical engineering. Investors interested in capitalizing on advancements in robotic design and function may consider established companies innovating in adjacent spaces. One such player is Oceaneering International, Inc., a recognized leader in deep-sea and remote robotics.

Oceaneering International Inc

Oceaneering International, Inc. (OII +3.74%) entered the market in 1964, seeking to provide high-end deep-sea diving equipment and robots to commercial clientele. The company is based out of Houston, Texas, and is regarded as a leading provider of unmanned marine, space, and other environmental vehicles.

Since its launch, Oceaneering International, Inc. has seen massive growth. Today, the company provides a plethora of services covering drones, subsea hardware, oilfield equipment, deepwater systems, and much more. The company currently employs 10,400 people and is one of the most recognizable names in its sector.

Those seeking exposure to the robotics sector should do further research on Oceaneering International, Inc. Its stock, OII, continues to climb alongside the company's yearly revenue. The firm currently has a market cap of $2.25B, which analysts predict will expand as demand for deep-sea drones increases.

As synthetic muscle technologies mature, firms like Oceaneering could benefit from crossover innovations in actuator performance and miniaturization—making them a stock to watch in the broader robotics ecosystem.

Latest on Oceaneering International

Obstacles to Overcome for Adoption

There are many obstacles that the engineers will now need to focus on. They will seek to improve the manufacturing process and even set up templates to help other researchers get their projects off the ground faster.

There will also be regulatory slowdowns in regard to integrating the technology into the healthcare sector. These checks and tests will take more time than commercial robotic uses but are necessary to ensure the products are of top-notch safety.

Synthetic Muscles Could Power Tomorrow’s E-Bikes and Beyond

When you examine the capabilities of synthetic muscles, it's easy to see a future where these actuators become more popular than their mechanically based counterparts. They use less energy, can be made easier, and are lighter. As such, the MIT engineers deserve a salute for their efforts that could revolutionize robotics moving forward.

Learn about other cool robotics projects now.

Studies Referenced:

^{1. Rossy, T., Schwendeman, L., Kohli, S., Bawa, M., Umashankar, P., Habba, R., Tchaicheeyan, O., Lesman, A., & Raman, R. (2025). Leveraging microtopography to pattern multi-oriented muscle actuators. Biomaterials Science. https://doi.org/10.1039/d4bm01017e}