Medical Design Briefs - July 2021 - 32

a
2 cm
300
Plaque Psoriasis
c
2 cm
300
Plaque Psoriasis
Lower Back
e
2 cm
250
Guttate Psoriasis
Lesion Normal
Fig. 1 - The team applies the device on the skin lesions associated with psoriasis on the arm (a),
hand (c), lower back (e) and the unaffected skin. Figure b, d and f show the results of stiffness variations
between unaffected skin and lesion regions. (Credit: Song, E., Xie, Z., Bai, W. et al./DOI number:
10.1038/s41551-021-00723-y)
PDMS, 200 µm
Copper Coil, 200 µm
PDMS Ring, 2.4 mm
Magnet, 1.5 mm
Polyimide Disk, 75 µm
Ti/SiO2
, 100 nm
Modulus Sensor, ~2 µm
PDMS Encap., ~30 µm
1 cm
Biological Tissue
Flexible Subs.
50 µm
Human Back
Back
5 cm
Fig. 2 - Schematic illustration of the mechanical actuators and sensors for quantitatively measuring the stiffness of biological surfaces. The lower-left
inset shows the device is more or less the size of a U.S. nickel. The other two pictures illustrate the sensing device arrays that support spatial mapping
of tissue stiffness. (Credit: Song, E., Xie, Z., Bai, W. et al./DOI number: 10.1038/s41551-021-00723-y)
32
Intro
Cov
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ToC
+
-
A
Medical Design Briefs, July 2021
µ
Actuator
VA
Coil
Actuator Array, 2.4 mm
Gauge
IS
VS
Tissue
Sensor Array,
2 µm
2 cm
Lesion Normal
f 500
Lower Back
∼110 kPa
Hand
d600
Hand
∼110 kPa
Lesion Normal
Arm
b
600
Arm
∼120 kPa
at tissue surface (typically micronscale), "
explains Dr. Yu. He pointed
out that cancer tissue is typically stiffer
or softer than normal tissue, and such
difference can be used as diagnostic
biomarker for a range of skin conditions,
like skin cancer or tumors under
the skin.
■ A Simple Structure
The electromechanical device's
thickness is only about 2.5 mm, and the
contacting area is about 2 cm². It operated
well on both hair-bearing and hairless
areas of the skin. Its working mechanism
is adapted from the basis of a
skin-integrated haptic interface for virtual/augmented
reality developed by
Dr Yu and the collaborators from
Northwestern University before.
The device works like this: after applying
an alternating current through the
copper coil, the magnet vibrates and
creates pressures onto the bottom surface
of the sensor (see Figure 2). This
would direct deformations that extend
to millimeter-scale depths of tissue,
which leads to periodic variations in
electrical resistance. Analyses of these
responses by simultaneously measuring
the voltage allow quantitative determination
of the stiffness of the tissues.
Each measurement could be done within
one minute.
The team then conducted clinical
studies on patients with skin disorders
with their newly invented electromechanical
device. The results indicated
a potential for accurate targeting of
lesions associated with psoriasis, showing
the practical medical utility of the
device. " The data produced can assist
in diagnosis, treatment tracking and
disease monitoring particularly for skin
Modulus (kPa)
Modulus (kPa)
Modulus (kPa)
È

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Medical Design Briefs - July 2021

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