Scientists
at University of Colorado, Boulder had developed a first and fully re-healable
and recyclable electronic material. This novel technology functions like
properties of human skin, capable of measuring pressure, temperature and
vibration. Technically, it’s a self-healing Robot - For instance if robots are
wrapped in an electronic material that mimics as human skin; theoretically it
can also sense objects that is too hot or too cold or if more or less pressure
needs to be exerted on an object. If this material is beyond repair, then it
can be soaked in a solution that separates out the silver nanoparticles then be
fully recycled into new usable material [1] (Figure 1).
Figure 1: Illustrates self-healing material developed at University of
Colorado, Boulder. Image Credit: Quartz [1].
Self-Healing Robots Breakthrough
Many
of natural organisms have the capability to heal themselves. Now, manmade
machines will be able to imitate this phenomenon. In the research Carnegie
Mellon University created a self-healing material that spontaneously heals
itself even under extreme mechanical damage. The soft composite material is
consisting of liquid metal droplets suspended in a soft elastomer. When it is
broken, the droplets rupture to form a new arrangement with adjacent droplets
and redirect electrical signals without any disruption. Circuits which are
created with conductive traces of such kind of material remain entirely and
continuously functioning when punctured, severed or material removed.
Applications for this kind of novel technology includes bio-inspired robotics,
wearable, computing human and machine interaction. Because material also
exhibits high electrical conductivity; it does not change when starched,
theoretically, it is ideal for use in power and data transmission.
“If
we have to build machines that are more compatible with the human body and
natural atmosphere, then we have to begin with new material types” was
confirmed by the author of the study [2,3] (Figure 2).
Figure 2: Illustrates a digital clock continues to run as damaged circuits
instantaneously heal themselves, rerouting electrical signals without
interruption. Image Credit: Nature Materials [3].
Delicate, Soft and Self-Healing Robot
A
new class of delicate and soft, electrically activated robots are capable of
imitating the expansion and contraction of natural muscles. These robots which
can be designed from a wide range of low-cost materials and are able to
self-sense and self-heal from electrical damage, representing a major advance
in soft robotics. A challenge in the field of “soft robotics” that can imitate
the versatility and performance. Nevertheless, Keplinger Research Group in the
College of Engineering and Applied Science has created a novel method of a new
class of soft robotics. This novel method of hydraulically intensified
self-healing electrostatic actuators abjure bulky, rigid pistons and motors of
conventional robots for soft structures that respond to applied voltage with
comprehensive range of motions. These soft robots can accomplish a variety of
jobs including holding subtle objects for instance, raspberry and a raw egg as
well as lifting heavy objects. These new tech robots actuators exceed the
strength, speed and efficiency of biological muscle and their flexibility. In
addition to assisting as hydraulic fluid which supports flexible movements, the
use of liquid insulating layer enables robots’ actuators to self-heal from
electrical damage. Another soft actuator that are controlled by high voltage,
also known as dielectric elastomer actuators; it utilizes a solid insulating
layer that fails catastrophically from electrical damage [4-6] (Figure 3).
Figure 3: Illustrates actuators can be designed as soft grippers to handle
and manipulate delicate objects, like this raspberry. Image Credit: Keplinger
Lab / University of Colorado Boulder [6].
Graphene for Artificial Skin in Self-Healing
Robots
Graphene
is a sheet of pure carbon atoms and it is known as world’s strongest material;
it is one million times thinner than paper. It is so thin that it can be viewed
as two dimensional. Although, it’s hefty price, graphene has become most
favorable nanomaterials due to its unique and multipurpose applications. One of
the organs in the human body; skin is known for its fascinating self-healing
properties. Imitating this phenomenon has proved too much of work as manmade
materials lack this technology. Due to stretching or bending and incidental
scratches, artificial skin used in robots are too much susceptible to ruptures
and fissures. In this study a novel solution where a sub-nano sensor uses
graphene to sense a crack as soon as it starts nucleation even after the crack
has spread a certain distance. Scientist subjected a single layer graphene
comprising various issues like pre-existing vacancies and inversely oriented
pre-existing cracks to uniaxial tensile loading till fracture. Once it is
completed, graphene started to heal and the self-healing continued irrespective
of the nature of pre-existing issues in the graphene sheet. Not to mention,
whatever the length of crack, they were all healed; provided the critical crack
opening distance are within 0.3 to 0.5nm for pristine sheet and sheet with
pre-existing defects [7,8].
Wolverine Inspired Material for Self-Healing
Robot
Researchers
at University of California, Riverside designed a novel method of an ionic
conductor, that means material that ions can flow through and it is
mechanically stretchable, transparent and self-healing. These materials have
wide variety of applications in extensive range of fields. It can give robots
to self-heal after mechanical failure. It also extends the lifetime of lithium
ion batteries used in electronics and electric cars; and improve biosensors
that are used in medical and environmental fields. This material was inspired
by wound healing in nature, self-healing materials repair the damage caused by
wear and extend the lifetime and in turn lowering the cost of the device. Ionic
conductors are a class of materials with vital roles in energy storage,
sensors, solar energy conversion and electronic devices.
The
vital problem is the identification of bonds that are stable and reversible
under electrochemical conditions. Traditionally, selfregenerative polymers
utilize non-covalent bonds which makes it difficult because these bonds are
affected by electrochemical reactions that decreases the performance of the
materials. Wang solved that critical problem by utilizing a novel mechanism
that is known as ion-dipole interactions; the forces between charged ions and
polar molecules that are highly stable under electrochemical conditions. In
this method, he joined a stretchable polymer with mobile and high ionic
strength salt to create material with the properties that scientist was
searching. It is a low cost and can be easily produce soft rubber like material
that can stretch 50 times its original length. If it has been cut, it can
completely heal in 24 hours at room temperature. As a matter of fact, after
only five minutes of healing the material can be stretched two times its
original length [9,10] (Figure 4).
Figure 4: Illustrates showing self-healing via ion-dipole interaction.
Image Credit: University of Colorado, Boulder [10].
Robots That Can Morph Metal Shapes
Researchers
created a novel hybrid material that is stiff metal, soft and porous rubber
foam that integrates the best properties of stiffness and as well as elasticity
when a change of shape is necessary. This material also has the capability of
self-heal if damaged. This material integrates with the soft alloy called
Field’s metal with a porous silicone foam and the rigidity and load bearing
capability of humans with the capability to drastically alter shape, like an
octopus. In addition to this, its melting point is 144 degrees Fahrenheit, the
major reason Field’s metal was taken because it has no lead in it. The
elastomer foam is immersed into a molten metal then it is placed in a vacuum so
that the air in the foam’s pores are removed and interchanged by the alloy. The
foam had pore sizes of around 2 millimeters that can be adjusted to make a
stiffer or more flexible material. In testing of its strength and elasticity
the material ability was deformed when heated above 144 degrees, then it
regained rigidity when cooled; then it returned to its original shape and
strength when reheated [11,12] (Figure 5).
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