Tangible digitization – Part 2

On the trail of the accessible tactile experience, the Mediasphere For Nature team continues with the development of an upscaled tactile model of a dor beetle. This article shows current project developments and provides an outlook on the final project stage. 

As reported in the first blog post, after the test phase with an early prototype, the fine-tuning of the digital model took place in the first half of 2022 (Figure 1).

Work on the original beetle at the museum  

After some initial fine-tuning work on the museum’s digital 3D model was completed at werk5, such as closing existing holes, the next step was to match the image of the model with that of the original beetle. To enable this, some high-resolution photographs of the animal were taken with the help of the museum’s digitization experts. These photographs help to recognize even the most delicate parts of the body and to adjust them accordingly on the 3D model (figures 2-3).

The result of the capturing process (figure 4) enables the modelling team to perform the one-to-one comparison of the original beetle with the 3D model in order to recreate the digital twin of the beetle as lifelike as possible.

Further research for the project was also carried out in the museum’s beetle collection. Among other things, it is planned to place audio trigger points at those spots on the beetle model where the mechanical sound production of the animal takes place. Enclosed is a sample recording of a dor beetle from the museum’s animal sound archive:

This form of sound production is called stridulation and is achieved by rubbing two body parts together: the so-called “pars stridens” and the “plectrum”. In the process, the toothed pars stridens brushes over the plectrum (see figure 6 below: pars stridens shown green, plectrum shown red). To ensure that the parts can be marked correctly for the model makers, an expert from the beetle collection closely examined the animal with the aid of a binocular microscope. Shown below is a display board that illustrates the principle of sound production through stridulation in a simplified way using the example of a grasshopper. 

Design of model and tactile station

Based on the experience gained with the first prototype, the design of the beetle model and the entire tactile station was continued. To enable easy mobile use of the model both inside and outside the museum, the unit was designed to be as compact as possible. The complete electronics are housed in the small base directly under the beetle model.

The layout and labelling of the touch station were designed in cooperation with the accessibility expert Ellen Schweizer. The station is divided into a horizontal surface where the headphones and the corresponding holder are attached. Below is the slightly angled text field, which will later on be provided with Braille and black print as well as individual sensory points.

In order to make the model more attractive for sighted users as well, a color was chosen that is as close as possible to the original beetle. While we used a neutral color for an earlier crocodile tactile model, the beetle will appear in a natural black tone (figures 9-10).

After various tests, we decided on a material mix for the model construction, whereby the largest part of the beetle body will be made of a robust mineral-organic composite material. This part of the model is made with a special large milling machine.

After milling the individual layers, they are pressed together until a stable structure is formed (figures 11-12). Here, the main body of the beetle is divided into an upper and lower shell. Both are joined together in a later process.

The finishing work on the shell halves is then carried out with the huge automated milling machine. Prior to the milling process, all presettings are entered in the associated complex control program. 

Delicate parts of the beetle model’s body are not created using a milling machine, but in a 3D printing process. The material used for this is a tough, long-chain plastic whose feel is somewhat reminiscent of cable tie material. The material is robust, but at the same time slightly flexible, which is primarily intended to reduce the risk of breakage in thinner areas such as the legs or antennae. Especially at the clawed foot ends of the beetle, the material still felt too fragile and unpleasantly spiky after the first test print, despite the considerable upscaling. In order to exclude the risk of injury when touching, the areas were marginally thickened. At these areas, therefore, the proportions now differ slightly from the original beetle. Attached (figure 15) you can see some test prints of the legs. After completion, the material will be painted black to match the color of the milled main part of the model.

Text work and outlook

After narrowing down the topics for the audio texts, suggestions for changes and adaptations from the user test group were incorporated. Among other things, the entire intro section was revised and two new topics were added. The texts are being tested among others by the museum’s education department and beetle department as well as by the model construction team and the accessibility expert. An Egyptologist has also reviewed some of the text sections – explanation to come at a later stage!

In the next blog post, we will report on the finalization of the beetle model and the entire touch station, including the installation of the sensors. In another workshop with the user test group, the installed sensors and the current status of the audio texts will be tested.