Mechanics/Fabrication Issues

I am in the early stages of creating a prototype of the PMC.

Initial objectives:

1. Effective sensor placement for useful breathing data.
2. Comfortable design for lengthy performances, easy on/off.
3. Minimize noise, maximize accurate data.
4. If possible, create haptic response system for performer.
5. Aesthetically pleasing and efficient design.



1. Effective sensor placement for useful breathing data.

The current design's sensor placement is based both on book-study of the respiratory system and on self-observation of breath-related body movements. As you inhale, the ribcage expands to the sides; since the right lung is slightly larger than the left lung due to the location of the heart, and is divided into three rather than two lobes, the right side of the torso is equipped with two sensors, and the left with only one. The diaphragm moves involuntarily with the breath, and a sensor is placed to capture this movement. While many technical studies of breath suggest that shoulders should not move, in observation of casual breathing it was clear that shoulders regularly move in breath patterns. Therefore, a sensor is placed to capture this vertical motion. Finally, the expansion across the upper back seemed worth capturing, so a sensor is placed between the shoulder blades.



2. Comfortable design for lengthy performances, easy on/off.

The challenge in the comfort of the design is that in order to enable the stretch sensors to gather accurate breath-movement data, at least one layer of the shirt must be skin tight. This has potential comfort-ramifications in both the physical and psychological realms, depending on the performer's comfort or lack thereof with wearing exposing clothing. In my design for the PMC, the issue of psychological comfort is addressed by creating a multi-layer design in which the top-layer is not form-fitting. The issue of physical comfort is addressed in a somewhat less satisfactory manner. The shirt has 4 layers, and will therefore be not only tight, but hot. This makes the ideal performance space somewhere that is cold, or at least cool. I will attempt to address these issues better in future revisions. Putting the shirt on, or taking it off, is not quite as easy as would be ideal, but it could be worse. I achieved a somewhat easier on/off by sewing together lots of key places in the layering of the shirts.

3. Minimize noise, maximize accurate data.

Minimizing noise is actually relatively simple in the PMC design, because both the changes in resistance provided by the stretch sensors, and the movement of the body during inhalation and exhalation, is relatively subtle. Therefore, the nature of the instrument inherently minimizes noise. Maximizing accurate data is more of an issue, due to the subtle nature of the instrument. Because of this, three of six stretch sensors (those placed on the side-body, at various places on the rib-cage), have been doubled-over in the shirt design, to double the changes in resistance with each movement. Two of the remaining three are placed in locations where it is easy for the body to exaggerate movements as necessary (the shoulder and between the shoulder blades). The remaining stretch sensor is placed on the front-body, between the bottom right and left ribcage. This stretch sensor will likely register the least amount of changes in resistance, but this is by design--this means that it can be used to trigger things only as desired, and with an exaggerated effort by the performer.

4. If possible, create haptic response system for performer.

This particular element will not be explored in this iteration of the project. Because a person can feel their own breathing, if they focus their attention, this seemed less important, and possibly redundant. The concept will be revisited in future versions, and a final decision will be made as to its usefulness and importance.

5. Aesthetically pleasing and efficient design.

The design that is visible to the audience is relatively efficient. While I find it aesthetically pleasing as well, some feedback has indicated that it may have more sci-fi/fantasy connotations than I desired. The placement of the stretch sensors made it very difficult to create an efficient path for all of the various strands of conductive thread, and therefore I settled for simply an *accurate* design. Layering helped keep the accuracy, and ended up being the most efficient course of action that I could determine.

Other Issues:

For the physical controller, I imagined that the trickiest element would be incorporating stretch sensors into the textile so that they moved; if each end of the sensors was not properly anchored, the data-change from the sensors would be limited or absent.

My initial sketches followed the following logic:

Knit fabrics are stretchy and will move with the sensor; this material should be placed underneath each stretch sensor. Woven fabrics, on the other hand, do not stretch, and make good anchors for the ends of the sensors. The woven fabrics need to also be anchored around the body, so that they do not simply move with the rest of the fabric.

In my first attempt to resolve this issue I designed a dual-layer shirt which incorporates knit fabric as the base, with a vest-like woven fabric anchoring top-layer. The hope is that the material will be firm enough, if wrapped around the entire torso, to provide the necessary anchor for the sensors.

I subsequently discovered that the anchoring was not as much of an issue as I had envisioned, and was able to use a knit tank-top as the base on which I sewed all of the stretch sensors.

Regarding the stethoscope-microphone, I was able to appropriate a cloth belt, on which I affixed the stethoscope, and in this manner I can attach the mic around the neck of the performer.