Potentials - July/August 2016 - 11

0.5 cm

Boundary

Underformed State

0.5 cm

Stretched

Compressed

(a)

(b)

(c)

Fig2 a series of optical images of a demonstration platform for skin-like wearable electronics (a) attached on the skin, (b) compressed,
and (c) stretched. (images reprinted with permission from aaaS/Science.)

bands, socks, or adhesive patches.
These devices have many important
capabilities for applications in athome health-care systems, but a key
challenge remains in the discomfort
of unsuitable sizes, weights, and
shapes for practical applications
during prolonged use.
Recent advances in materials,
mechanics, and manufacturing technologies have led to ultrathin, lightweight, and stretchable "skin-like"
wearable electronics that can conformably laminate onto the surface
of the skin and are mechanically
invisible to the user. A representative example device appears in Fig. 2,
in which the device platform is
equipped with a broad collection
of electronic sensors for temperature, strain, pH, and electrophysiological signals to monitor electrical,
chemical, and mechanical activities
through the skin. Here, the printed
arrays of semiconductor nanomaterials (i.e., silicon nanomembranes) that are configured with
serpentine (stretchable) interconnectors ser ve as active sensing
components. The stretchable design configurations that typically
comprise device islands connected by serpentine interconnects
allow the entire device structure
to accommodate large deformations without fracture, yielding
high levels of stretchability. These
strateg ies aim to isolate the mechanical deformations to the elastomers, thereby significantly reducing principal strains in the rather
brittle device materials.

The design configurations can
also combine multilayer neutral mechanical plane layouts to offset the
induced tensile/compressive strains
in the device materials under bending. Clinical utility of these types of
devices exists for skin-mountable
biomedical applications that need to
run in a rapid, mechanically flexible,
and noninvasive manner. Examples
include those for real-time monitoring of temperature, pressure, stiffness, and vascular blood flow rate
through the skin.
The products are equipped with
various electronic modules, such
as accelerometers, gyroscopes, and

physiological sensors, allowing to
wirelessly provide first-hand data to
medical researchers. The technology
is expected to play an important role
in future monitoring systems for motion disorders such as Parkinson's
disease or neurodegenerative disorders, as a representative example.

soft core/shell packages
Many clinical applications involve
the mounting of such electronic
systems on the surface of the skin,
which requires an efficient packaging system to protect the devices
from environments as well as to
minimize the interfacial stresses

Shell
Core

Electronics

1 cm

Fig3 an optical image of a core/shell packaging structure applied on the wrist during
dumbbell lifting. the inset shows a cross-sectional illustration of the representative layers in a core/shell structure with embedded stretchable electronics. (images reprinted
with permission from wiley-Vch.)

IEEE PotEntIals

Jul y/August 201 6

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Table of Contents for the Digital Edition of Potentials - July/August 2016