STAMP and 3D Printing Used to Create Artificial Muscles for Medicine and Robotics

Artificial skeletal muscles are particularly important for the development of in vitro models for disease research or for use in biohybrid robots. However, there are some difficulties in the traditional production of these muscles, as 2D muscle monolayers often peel off after a few days and are not suitable for long-term use or live cell imaging – a technique in which cells are examined in a living state under a microscope or other imaging technique. For this reason, scientists at the Massachusetts Institute of Technology (MIT) have now applied a new technique to artificial muscle tissue that contracts in multiple directions and mimics movements of natural muscles. In the study, they presented a microtopographic stamping method that precisely controls the alignment of muscle fibers, and additive manufacturing played a particularly important role in this. The muscles could potentially be used in regenerative medicine, muscle disease research and robotics.

The new process “Simple Templating of Actuators via Micro-Topographical Patterning” (STAMP) uses 3D-printed stamps to structure microscopic grooves directly in natural hydrogels. The 3D-printed stamp is used to incorporate structured grooves into a soft hydrogel. These grooves guide the muscle cells as they grow and ensure that they align into functional fibers that can contract in different directions.

Top left: CAD model of the micro stamp and holder; top right and bottom: resulting 3D-printed parts.

But how exactly does the procedure work? The first step is to produce the 3D-printed stamps. These fit into 24-well plates and have fine vertical grooves (12.5-125 μm). The stamps are then fixed in a holder with bubble release and a liquid consisting of fibrinogen and thrombin is poured into the wells. The whole process is incubated at 37 °C for about an hour so that the fibrin polymerizes to form a cross-linked hydrogel. After removing the plunger, the hydrogel shows a precise, regular groove structure and a smoother surface, which improves the conditions for cell culture. The stamps are sterilized before use and can be reused several times after cleaning.