Professor Michel Maharbiz
is developing smart bandages that read
electrical fields to track wound healing.
Bandages to Track Wounds Through Healing
November 4, 2013
(Above: Printed sensor array on flexible
polymer substrate of a type to go under a bandage and track wound healing.
Courtesy Michel Maharbiz)
by Gordy Slack
Most scrapes and boo-boos heal quickly and completely with traditional,
over-the-counter bandages. However, for deeper cuts or surgical incisions,
something more is needed so that physicians can monitor the healing process
happening underneath the bandage. “Right now, if you have a bandaged wound, the
only way to tell its status is to remove the bandage and look,” says Michel Maharbiz,
Associate Professor of Electrical Engineering and Computer Sciences at UC
Berkeley. Neglecting to inspect wounds can allow infections and other serious
pathology to go undetected and untreated. But removing a bandage may expose a
wound to infections, disrupt the healing process, or structurally damage the
Maharbiz is working with colleagues to develop a bandage
that reads electrical fields naturally emitted by wounds to track the rate and
extent of healing. This new tool could potentially be applied to internal
surgical sites and sutures, tracking internal healing and then wirelessly
sending data out of the body to an external processor. Currently, there is no
good way for doctors to track progress of internal wounds so this bandage could
be used in numerous situations.
The project, called FRONTS (Flexible Resorbable
Organic Nanomaterial Therapeutic Systems) and sponsored by the NSF,
employs an interdisciplinary group of researchers from UC Berkeley and UCSF, to
develop the bandage device. Maharbiz focuses on the
project’s nanosensors, but the group also includes
specialists in printed electronics, biocompatible materials, surgical devices
and procedures, and the physiology of wound healing.
After an injury, epidermal cells replicate and
move into the area of a wound in order to close it up and start the healing
process. This causes ionic concentrations to shift, a change that generates
subtle but characteristic electrical fields. The fields are detectable by
sensor arrays that can be printed onto a flexible substrate that is part of the
bandage itself. UC Berkeley EECS Professors Vivek Subramanian
and Ana Claudia Arias head the electronic
printing efforts and can print circuits, sensors, and batteries on all kinds of
flexible materials, including biocompatible ones that are “thin, light,
flexible, and disposable,” Subramanian says.
“To get data out of the wounds we need a thin-film battery, we need electrodes
to do measurements, and, in the longer term, if we are going to put this inside
the body, we need electronics that will dissolve away,” notes Subramanian.
It has long been known that wounds, when healing, create signature electrical
fields. “But no one has done a good job of putting all of this information
together to build good models of wound healing, and make those models
tractable, make them useful in the clinic,” says Maharbiz.
The novel step embodied in the FRONTS project is the detection and precise
measurement of those fields over time, thereby non-invasively tracking the
healing process. Together with Maharbiz, Subramanian
is developing ways to automatically interpret and analyze the electrical
signals given off by wounds.
For simplicity’s sake, the first application for such bandages would be on
damaged tissue on the outside of the body. “For on-skin measurements,”
says Subramanian, “the materials do not have to dissolve; they are just
thin-film printed systems integrated into bandages.”
The on-skin concept is currently being tested on animals
models at the University of California in San Francisco. Shuvo Roy,
a UCSF professor in bioengineering, and Michael
Harrison, a pediatric surgeon and professor emeritus also at UCSF,
are preparing for clinical human trials if the animal models are successful.
“We already have a clinic and a practitioner in the plan so we can move quickly
to testing the bandages in the clinic,” says Maharbiz.
The group is developing a more complex and challenging version of the bandage
as well. It relies on the same principles, but this array of sensors would be
left inside the body after surgery in order to track the healing progress of
internal lesions created during surgery. In those cases, unless doctors reopen
the surgical site, it is impossible to track how fast and well a wound is healing.
The sensors themselves could be embedded deep in the abdominal cavity at the
site of the wound but have a thin tail-like antenna connecting them to a chip
near the skin that sends the data to a receiver outside the body.
The body tends to reject equipment left inside it for very long, though, so the
research group is experimenting with non-toxic materials that will biodegrade
and be absorbed by the body. Everything from the batteries to the circuit
boards must be biocompatible, non-toxic, and resorbable,
Beyond just tracking the progress of healing wounds, the group is hoping
eventually to influence that healing by the introduction and manipulation of
electrical fields. This part of the project is “still pretty speculative,” says
Maharbiz. However, there is strong evidence, he says,
that wounds not only produce electrical fields, but that whole communities of
cells—particularly epithelial cells—are also responsive to them. The electrical
disturbance to epithelial cells created by a wound is immediate and is thought
to trigger a process known as galvanotaxis in which
cells proliferate and migrate to the site of injury. By manipulating the
electrical fields around a wound, it may be possible to influence how it heals,
minimizing harmful scar tissue and maximizing the chances for full and robust
recovery, says Maharbiz. “It would help doctors gain
control over how the healing takes place, more than just making it go fast.”
Applying electrical fields is a much trickier engineering and clinical problem
than just reading them, says Maharbiz, because these
fields may cause unintended electro-chemical side effects (in addition to
tissue healing) that doctors would first have to understand and control for.
Roy is also investigating additional sensors that could be made part of a
bandage system to track more kinds of information emitted by wounds: pressure
and oxygen sensors, for example, could help detect the emergence of pressure
ulcers, a common problem for hospital patients who remain in one position for a
long time. With the population getting older and assistive care becoming ever
more prominent, a device that can assist with preventing ulcers in patients
would be very useful.