(8.33 × 10−4 + 1.36 × 10−5)/200 = 4.24 × 10−6 kg

As can be seen from Table 6-7, the type of user interface and the type of data selected can have a dramatic impact on the energy consumption and consequent weight of the system. For example, a 10-second color video clip without compression would require 37.5 g of battery weight. Table 6-7 shows that the user interface design can affect energy consumption and battery weight by four orders of magnitude.


Society has historically evolved its tools and products into more portable, mobile, and wearable form factors. Wearable implies the use of the human body as a support environment for the object. Clocks, radios, and telephones are examples of this trend. Computers are undergoing a similar evolution. Simply shrinking computing tools from the desktop paradigm to a more portable scale does not take advantage of a whole new context of use. While it is possible to miniaturize keyboards, human evolution has not kept pace by shrinking our fingers. There are minimal footprints beyond which objects become difficult to manipulate. The human anatomy introduces minimal and maximal dimensions that define the shape of wearable objects. The mobile context also defines dynamic interactions. Attempting to position a pointer on an icon while moving can be tedious and frustrating.

Wearability is defined as the interaction between the human body and the wearable object. Dynamic wearability includes the human body in motion. Design for wearability considers the physical shape of objects and their active relationship with the human form. Gemperle et al. (1998) explored history and cultures, including topics such as clothing, costumes, protective wearables, and carried devices. They studied physiology and biomechanics, movements of modern dancers and athletes. Also drawing upon their experience with over two dozen generations of wearable computers representing over a 100 person years of research, the results were codified into guidelines for designing wearable systems. These results are summarized in Table 6-8, which could be used to guide system designers of future warrior systems.

TABLE 6-8 Design-for-Wearability Attributes for Computers

Attribute Relating to:



Identify where the computer should be placed on the body. Issues include identifying areas of similar size across a population, areas of low movement/flexibility, and large surface areas.

Humanistic form language

The form of the object should work with the dynamic human form to ensure a comfortable fit. Principles include inside surface being concave to fit body, outside surface being convex to deflect objects, tapering sides to stabilize form on body, and radiusing edges and corners to provide soft form.

Human movement

Many elements make up a single human movement: mechanics of joints, shifting of flesh, and flexing and extending of muscles and tendons beneath the skin. Allowing for freedom of movement can be accomplished in one of two ways: by designing around the more active areas of the joints or by creating spaces on the wearable form into which the body can move.

Human perception of size

The brain perceives an aura around the body. Forms should stay within the wearer’s intimate space, so that perceptually they become a part of the body. (The intimate space is between 0 and 5 inches off the body and varies with position on the body.)

Size variations

Wearables must be designed to fit many types of users. Allowing for size variations is achieved in two ways: (1) use of static anthropometric data, which detail point-to-point distances on different-sized bodies, and (2) consideration of human muscle and fat growth in three dimensions using solid rigid areas coupled with flexible areas.


Comfortable attachment of a form can be created by wrapping the form around the body, rather than using single-point fastening systems such as clips or shoulder straps.


The system must have sufficient volume to house electronics, batteries, and so on, which in turn constrains the outer form.


The weight of a wearable should not hinder the body’s movement or balance. The bulk of the wearable object weight should be close to the center of gravity of the human body, minimizing the weight that spreads to the extremities.


Before purchasing a wearable system, one should walk and move with the wearable object to test its comfort and accessibility.


Passive and active sensory interaction with the wearable should be simple and intuitive.


The body needs to breathe and is very sensitive to products that create, focus, or trap heat.


Culture and context will dictate shapes, materials, textures, and colors that perceptually fit users and their environment.


SOURCES: Gemperle et al., 1998; and Siewiorek, 2002.

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