Choosing a topic

The most common science demonstrations are easy, quick, and visually interesting (15, 16). We wanted to create a novel outreach activity that had these attributes but was also tailored specifically to the interests of local children. In addition, we wanted a display that went beyond simple cool science to ideas that had everyday applications for nonscientists. We also wanted a theme that channeled the knowledge of the creators. In our case, the authors have research interests in muscle diseases, so we decided early in the design process that our displays should incorporate muscle or neuronal biochemistry. In considering this topic, the engineering students were struck by how similar descriptions of the action potential and actin and myosin crossbridge formation were to processes they were learning in electrical and mechanical engineering classes. This inspired us to design the project around the similarities between neuromuscular biochemistry and robotics. Scientifically, we aimed to explain how your nervous system conducts electricity through neuron depolarization and then how muscle cells respond to this electrical impulse through actin and myosin crossbridge formation. We reasoned that this topic is relatable to everyone: all children think about how they move or how strong they are, and all parents bear witness to the kids' increasing coordination and strength.

Design criteria

In following both the engineering and the pedagogic backward design process, we spent significant time defining requirements that would be critical for successful fair displays:

• (a) The display must have a hook, a way to gain initial attraction to visit the display booth, which extended beyond the science. In addition, this hook must have wide appeal to children and be fair glitzy; we are, after all, competing with rides on the midway and funnel cakes.

• (b) The science presented must be obviously relevant to everyday life.

• (c) The science involved must map to specific state-dictated STEM learning objectives from K to grade 8 (or higher). This allows these exhibitions to serve as school outreach displays during other times of the year. At the beginning of the design process, we defined specific learning objectives for each age level, and these objectives guided the display design.

• (d) The display must be interactive across a wide age range.

• (e) The display must be rugged enough to survive a fair, with the potential of being in an outdoor booth with rain, mud, animal poop, or indoors with crowded conditions and kids' sticky cotton candy fingers.

• (f) The display must be able to be left alone overnight without significant safety or security issues.

• (g) The display must be transportable in a normal-sized truck and movable over rough surfaces.

• (h) The display must be able to be easily assembled, disassembled, and fixed by volunteers who did not initially design or make the display.

• (i) Each display's story must be completed quickly, preferably under 2 min.

• (j) The display must be large enough to see from at least 10 ft away.

• (k) The entire ensemble of displays must fit in a fair booth space (10 × 10 ft was standard for our fair).

Criteria (c), (h), (i), and (j) are common for STEM outreach activities. In contrast, criteria (a) and (b) are not normally strongly considered when designing outreach activities, and criteria (d) to (f) preclude the use of most instrumentation, chemicals, and specimens that are normally found in science outreach activities.

Specifics in addressing the criteria

Design criterion (a) requires the most preplanning and must be considered before the other criteria because it dictates what the eventual outreach activity will entail. This step took several months to develop. To best connect with rural families, we first considered a farm-specific display. Specifically, we explored a booth theme on how genetic alterations could increase crop yield and animal dressing percentage. This idea was abandoned for 2 main reasons; we suspected that although this would be interesting to the parents, it would not hold the interest of children and thus violate criterion (a). Also, genetically modified organisms have become political, which could undermine our goal to forge connections with the community (17).

We next considered topics that addressed health concerns of rural families. Rural communities tend to have higher rates of chronic health problems, including cardiovascular disease (18). We designed experiments to visualize how both electricity and chemicals stimulate normal (and abnormal) muscle contraction by reanimating chicken feet or pig hearts with a battery or potassium chloride. Although this would certainly be interesting and educational, we could not devise a viable strategy to satisfy criteria (f) and (j). Exploring this theme further, we considered topics that would allow us to talk about both engineering and muscle biology; the idea of a living machine. Such a display does not have to involve (often small) biologic material, which is a positive. In addition, this concept is prevalent in pop culture, especially in science fiction and comic books. To gauge interest, we surveyed over 500 local elementary school children (K to grade 5) in 5 local schools about half-machine and half-human fictional characters. In 2020, students liked Ironman the most, although all the characters we listed (Characters in the movie Inside Out, Winter Soldier, Baymax, and Luke Skywalker) were almost equally popular (Supplemental Fig S1). Luke Skywalker and Ironman had almost universal name recognition among our survey participants.

Using superheroes to engage with students is not unique; others have successfully melded science and superheroes to engage a wide variety of students from grade school through college (19–23). This theme seems to transcend demographic and socioeconomic barriers particularly effectively (24). Of note, the Marvel franchise is quite popular with rural student's parents, helping attract families to our booth (24). The drawback of using pop culture, and perhaps one reason it is not used even more often in outreach activities, is the potentially short shelf life of a given character.

One initial concern with using a commercial character was copyright laws. In consultation with members of our arts and media department, we found that the US government's fair use policy exempts displays such as this from most name and likeness copyright rules (25). Our exhibition did not sell anything, was adapted for a specific educational purpose, and used modified images that were pertinent to educational goals. We suggest checking with either institutional lawyers or media experts at this stage of idea development just in case. Being easily recognized and enticing to children (and parents) was especially important in the high-distraction environment of the fair. Despite the necessity of an additional precautionary legal step, we recommend using pop culture icons in this type of display.

Because our work was conducted in Virginia, criterion (c) dictates that we align our lessons to the Virginia Standards of Learning for grades 3 to 6 (Supplemental Table S1). Taking the time to consider what children already know, what they are learning about, and where they are developmentally was an important prerequisite for all volunteers. This helped calibrate the story to an appropriate educational level. Our approach of integrating state assessment tools into our display differs from traditional backward design; in our case, most of the assessment tools are preexisting. We defined the larger learning objectives and then developed signature activities that meet those objectives with guidance from the state-sponsored assessment for a variety of grade levels. A table outlining this pedagogic method and age-specific outcomes was distributed to local teachers who interacted with our booth, and this made it easier for us to integrate these displays with local schools and conduct additional outreach events during the school year (Supplemental Table S1). In short, the process of mapping STEM topics to various education levels drastically increased the versatility of our displays and expanded our stakeholder base to local schools.

We found that criterion (d), creating an interactive display, was one of the more difficult benchmarks to achieve effectively. Much of science and most science demonstrations involve observation, but children often learn better when they touch and manipulate the objects they are studying (26). Interactive displays help maintain kids' interests and also allow them to physically become part of the learning process (27). In exploring this design necessity, it became clear that many options are not viable due to safety issues, space concerns, or other restrictions. Thus, our displays used mainly push buttons, cranks, and picking up golf balls, so this particular project had no specific safety precautions. However, even these safe options presented unforeseen challenges for inclusive involvement. For instance, buttons needed to be placed at a reasonable height to accommodate both kindergarteners and middle schoolers. Discovering these hidden impediments to a broad audience necessitated that we test our displays with many children of different sizes during the design phase. This testing also alerted us to just how unpredictable children can be; students would sometimes push, hit, or otherwise abuse the displays. Although the displays were designed to withstand this kind of environment (criterion [e]), it, nonetheless, underscored the need that children have adult supervision while interacting with and visiting our displays.

Additional considerations

In total, our fair booth had 4 displays. This required a minimum of 2 volunteers, and 3 were preferable. At any given time, 1 volunteer is talking to a group of children, and the other is resetting the displays. We only staffed our booth from 3 to 9 PM, during the busiest times of the fair. The displays were unplugged and draped with cloths when we were not present. Because manning this booth requires significant time and effort, we tried to pay students with help from the university outreach office. We also contacted our local academic fraternities, such as Alpha Chi Sigma, Beta Beta Beta, and Theta Tau, to help man the booth because students in these clubs need a certain number of outreach hours, and the fair provided an excellent way to accumulate these hours quickly.

Lesson 1: neural connections

The first display, and the main attraction to our booth, is a printed poster of an 8-ft tall Ironman mounted onto plywood (Fig 2A). Four buttons, one for each limb, when pressed send a ping-pong ball through visible tubes from Ironman's brain to a specific hand or foot, where a light turns on to simulate Ironman's suit thrusters. The display functions by connecting Vex motors (Vex Robotics, Greenville, Texas) to the buttons. When a button is pressed, the motor turns a paddle wheel, releasing one ball stored in the hopper through the acrylic tubing, and also activates another motor group that opens and closes various ducts to guide the ball to the correct location (Fig 2B). Each hand and foot light up, and this is synchronized to activate once the ball reaches its designated location. This represents nerve impulses traveling from the brain through the spinal cord to the extremities. In practice, this display appeals most to younger kids (pre-K to grade 4). Our explanation of this phenomenon includes active participation such as asking the child to make a muscle themselves or kicking an imaginary soccer ball, as well as the built-in interactive visual cues on the display that describe how information travels from your brain to your extremities. Both examples of engagement connect this science lesson to everyday life. Older children (and adults) are more drawn in by the electrical and mechanical components of the display, which are readily visible. Specifically, people can see the electrical wiring, the tube network that includes several 3-dimensional (3D) printed pieces, and the small motors that control the ball path. This kind of open design, thus, provides multiple avenues of initial engagement, from biochemistry to engineering.

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Our learning objective for this display was for participants to explore how the brain communicates with the body. In subsequent displays, this was expanded to include a variety of different scales, from subcellular through system biology. Using storytelling and call and response, we addressed multiple levels of Bloom's taxonomy (Supplemental Fig S2): name the structures involved in these signaling events (remember); recall and explain what is happening at each stage (understand); connect the different stages together (apply); and at the end of all the lessons, explain how the brain can control a myoelectric prosthetic (analyze).

Lesson 2: membrane depolarization

The second display connects the macromolecular concept of neurons relaying signals to the biochemical concept of membrane depolarization. Because biochemical gradients are both ubiquitous and often hard to understand, we aimed for a simplistic yet accurate display that only involves a single ion pump and a single ion pore (Fig 3A). When describing this process, we use gravitational potential energy as a proxy for a concentration gradient. Golf balls, which here represent ions, start on a retractable shelf at the top of a large hollow box with an acrylic sheet over top. This shows the high concentration of ions at the beginning of the biologic process. A button on the side of the board retracts a solenoid that was holding the shelf in place, thus releasing the shelf from its upright position (Fig 3B). The ions then fall (in a manner that resembles Brownian motion) through several ion channels that are built into the board into the collection basket below. To reestablish the concentration gradient, children must actively transport the balls from the bottom basket back up to the top shelf, in a similar energy-requiring mechanism to that of an ion pump. We point out that the hard part in creating this system is establishing the gradient and that the activation signal is relatively minor. We relate this to Ironman by pointing out that this biologic system, like an electrical wire, moves electrical charges. Because both neurons and electrical wires move charges through a system to relay information, our bodies act very similarly to an electric machine.

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Our learning objective for this lesson is for participants to understand how electricity can enter a cell in the form of ion flux. Again, through storytelling and call and response, we ask participants to name the stages of membrane depolarization (remember), recall what happened at each stage (understand), and connect the neural signal (ping-pong ball) from lesson 1 to the membrane depolarization in this lesson (apply).

Lesson 3: muscle contraction

The third display aims to teach participants about actin and myosin crossbridge formation. Rotating gears, powered by a child turning a crank, move a series of paddles, resulting in the pushing of a ladder over a track installed on the top of the gears (Fig 4A). The gears and paddles represent myosin, and the ladder represents actin. As the 2 symmetric cranks are turned, the myosin paddles drive the 2 halves of the actin ladders closer to the center of the sarcomere. These cranks can only be turned if a lever that controls a mechanical wedge and exit pallet is first disengaged. This lever represents calcium and teaches children that there are 2 requirements to initiate muscle contraction: calcium and energy. The gears in this display were printed 3 dimensionally, and the frame was constructed from aluminum extrusion piping. The actin ladder was created from a polyvinyl chloride pipe, and the myosin heads were made of aluminum piping. The gears were designed to have holes that could fit metal bearings, which held the myosin heads. This allows the heads to oscillate in a rowing motion when the gear rotates. As the gears are turned, each head will come into contact with the actin ladder in a sequential pattern and push this ladder closer to the center. When describing this lesson, we repeat the action from lesson 1, such as making a muscle, and this time talk about the physical muscle movement. To link this to Ironman, we point out that muscles look similar to small machines in your body. We assess participant learning by asking them to recall how the brain sends signals (remember) and how cells receive signal via electricity (remember). We then ask participants to explain to us how muscle cells convert this electrical energy into mechanical energy (apply).

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Lesson 4: practical application

To tie each lesson to our central theme and to show why these lessons are practical in the real world, our fourth display is a mechanical arm connected to one of our student helpers with an electrical lead (Fig 4). The mechanical arm is controlled by the electrical impulses in the person's arm measured through a muscle sensor and is activated by a bicep curl, thus providing direct proof that we have electrical signals controlling our muscles. To create a small and inexpensive display of what the biologic electrical signal looks like, we programmed a Raspberry Pi system (Cambridge, UK) to visually display the electric readout on a small liquid crystal display screen (3 × 4 in). This electric readout also interfaces with a custom MATLAB, version R2023a (The MathWorks, Natick, MA) code to control the mechanical movement in the 3D printed arm (Supplemental Material). If the readout is below a certain threshold, the arm remains down, and if the readout is above the threshold, the arm moves upward, mimicking the motion of the person connected doing a bicep curl. Depending on the inclination of the children, this might lead to conversations about how “we are just like Ironman” or how this technology underlies modern prostheses, or how this technology could be useful on the battlefield. The tendency of participants to use these basic science concepts as a jumping-off place for other ideas was both common and encouraged. Our primary learning objective for this lesson was to understand how engineers use the body's own processes to create myoelectric prosthetics (analyze).