Today, the methods used to monitor patients in the hospital are cumbersome, expensive, and often inconvenient, both to patients and providers. Each device tends to come with its own bundle of wires and electrodes, tethering the patient to equipment at the bedside and preventing them from moving around easily. As walking around has been shown to shorten recovery time, this is counterproductive. Disconnections caused by patients getting up or tossing and turning in bed also may be a cause of alarm in clinicians, who end up disturbing their patients or worrying over minor technical issues.
We felt there had to be a better way, something that didn't tether a patient to the bed, and was comfortable enough that they wouldn't mind wearing it.
What it does
A temporary tattoo is placed on a patient's arm. The tattoo is composed of a special carbon-based conductive ink that can function in lieu of medical electrodes. This allows us to accurately measure a patient's EMG signals (muscle activity) through the use of a differential voltage amplifier. The mini Bluetooth Low-Energy (BLE) micro-controller directly next to the tattoo sends this EMG signal information over to an Android Things NXP i.mx7d single-board computer, which hosts a BLE server so that the micro-controller can send this data over wirelessly to the NXP board.
How we built it
There are two distinct parts to the Tattoo Care health solution - the NXP board enclosure, designed and manufactured to be situated on a patient's bed stand, the actual tattoo, and the accompanying electronics parts designed for the patient to wear. To build the NXP board enclosure, we first designed and modeled an ergonomic, efficient container using the Solidworks software. This model was based on the precise measurements of the touch screen display and NXP board's dimensions. Using the University of Pennsylvania's machining facility, we laser-cut the enclosure out of acrylic, forming a container for the base station. The NXP board was then loaded with the Android Things OS and had the sample Bluetooth GANTT server code heavily modified to accept data sent by the Arduino micro-controller.
The tattoo was created using a combination of conductive paint, tattoo paper, and a stencil tool.
Challenges we ran into
Bluetooth Low Energy (BLE) is extremely difficult to implement, especially in the course of a weekend.
Finding a bluetooth microcontroller that would work and was relatively small.
Learning Android - also not easy in the course of a weekend.
It took many trials and iterations before we came up with an application process for the conductive material that would allow the tattoo to retain both physical and electrical integrity (as well as not irritating the skin).
Having to downscale from our original scope, as a result of other complications.
Accomplishments that we're proud of
- Getting BLE to work
- Creating the container
- Rigging up the tattoo
What we learned
We learned how to use an oscilloscope, how to solder, how to use Android Things, how to circuit everything, what is an EMG, possible ways of monitoring patients,
What's next for TattooCare
We'd like to explore topics such as piezoelectric energy harvesting to allow for a solution that can operate without the need for any power input. We'd also like to explore the use of nanomaterials for something that applies more cleanly to the skin and is longer lasting.