Hi, I'm Katherine Song.
This is a presentation of our paper, "Vim: Customizable, Decomposable Electrical Energy Storage."
The word vim means vigour, energy, or 'go.'
This is the name that we give to the electrical energy storage elements that we have developed
and will describe in this talk.
Our motivations for Vims are two-fold.
First, providing electrical power is essential for nearly all interactive technologies, yet
it often remains an afterthought in the design and prototyping processes.
Power conventionally comes in the form of rigid batteries, which come in set sizes and
geometries.
When integrating batteries into small, low-power, and temporary electronics designs, it is not
uncommon to find that the design must physically expand to account for and enclose batteries
that outsize the rest of the system, both in terms of physical footprint and electronic
capabilities.
With Vims, we propose that instead of leaving power as an exercise for later, we elevate
it to be a first-class design element that can be developed alongside and iterated upon
with the rest of the components of an interactive system.
Secondly, conventional batteries present a serious sustainability problem and are some
of the most environmentally hazardous components of electronic interactive systems.
They rely on toxic metals, such as cadmium, lead, or lithium, that are extracted through
resource-intensive processes and must be carefully contained at end of life.
Lithium ion batteries that are improperly disposed of in regular landfills can cause
fires, endangering nearby communities.
The lack of sustainable energy storage alternatives is a substantial obstacle in the path of the
collective efforts among the HCI community of makers to create eco-friendly interactive
systems.
There are several noteworthy approaches that we draw inspiration from in thinking about
how to reduce electronic waste and design more sustainable energy storage solutions.
For example, researchers have created self-sustaining and battery-free systems that can be powered
wirelessly through inductive chargers, NFC, ultrasound, and even ambient backscatter from
electromagnetic energy from TV signals, WiFi, Bluetooth, and radio, for example.
Vims add yet another approach to this increasingly rich pool of techniques and are especially
attractive for temporary applications that cannot be powered from ambient energy harvested
from the environment.
Now I will discuss how we designed Vims.
Vims are, in essence, supercapacitor structures that can be made from a variety of household-safe and
even edible materials.
A supercapacitor can be made using just 3 different types of materials: first, a very conductive
current collector, second, a conductive but porous electrode, and finally, an electrolyte with mobile
ions.
For our exemplar Vims, we use graphite as a current collector, activated charcoal bound
with CMC and water as an electrode, and table salt, glycerin, and CMC as an electrolyte.
The fabrication of Vims takes minutes and is done with entirely DIY-friendly methods
and safe materials.
First, an electrode ink is mixed by combining activated charcoal, CMC, and water.
Next, an electrolyte composed of glycerin, salt, and CMC is mixed.
The electrode ink is then screen-printed onto a conductive current collector, such as graphite
foil.
After drying, the electrolyte is bar-coated onto the electrode and then dried again.
Vims are completed by then cutting the prepared pieces and pressing them into a sandwich.
Vims may be shaped, reshaped, and cut into different geometries, and by using different
materials, such as edible gold leaf instead of graphite, we can also achieve different
aesthetics that can be customized to the application.
Under a constant-voltage charging scheme, Vims can be charged to 2 Volts within 5 minutes.
Vims may be more quickly charged by using a constant-current charging scheme with higher
current.
Under a charging current of 100milliAmps, a Vim reaches 2Volts in just 5 seconds.
Thanks to their flexibility to charge under varying current, Vims can also directly be
connected to solar panels or other energy harvesters without the need for a charge regulator.
A single Vim can readily power small electronic components like LEDs.
By chaining 4 Vims in series, we can create storage elements that can be charged to 10 Volts
in 3 minutes and can power a 3.3 Volt device for over 24 hours.
Vims can double as decorative elements and a power source, powering some electronics,
like this clock, for an entire day.
After fabrication, Vims may be bent, rolled, cut, or reshaped.
Their electrical characteristics are virtually unchanged during and after bending to 90 degrees.
Vims made with our exemplar recipe do not dry out or warp over time.
Thus, Vims are stable for months when stored under ambient indoor conditions.
We charged and discharged Vims over 100 cycles across 3 months with no noticeable change
in performance, which is in line with what we would expect from supercapacitors.
Vims can be combined with other novel, degradable electronics to create systems that are decomposable
in backyard conditions in their entirety.
Fashion is a domain that is fitting for fully decomposable interactive interfaces.
Notably, some accessories are only appropriate to don in certain occasional situations.
With this in mind, we developed a very low-power, 100% decomposable on-skin display.
Operationally, the system is a 2-state electrochromic display whose transformation is triggered
by the application of a lotion, cream, or other electrolytic gel.
The display comprises a paper tape substrate with a single layer of PEDOT:PSS, a common
conductive polymer that is non-cytotoxic and becomes biodegradable in the presence of hydrogen
peroxide, which is widely available and environmentally friendly.
The PEDOT ink is highly conductive and electrochromic, serving as both an electrode and an active
electrochromic layer.
When lotion is applied, free ions migrate towards the electrodes and cause redox reactions.
PEDOT:PSS becomes noticeably darker under reduction, leading to color changes in the
design that saturate in a couple of seconds.
The on-skin display is quasi-bistable and can hold its color-changed state for over
10 minutes or until the lotion is wiped off or absorbed by the skin.
A chain of 4 Vims, which can be mounted onto the skin as a bracelet, holds more than enough
charge to power this wearable over the course of a whole day with multiple lotion applications.
Vims may also be used in future edible experiences.
By definition, eating is an experience that is ephemeral and thus potentially another
domain for which Vims are ideal.
Our exemplar Vim design may be made fully edible by replacing the graphite current collectors
with edible gold foil, enabling new, sustainable interactions during the experience of eating.
This is a plot of the current of an edible Vim when shorted through a 47kΩ resistor,
which approximates the resistance of a human tongue.
Based on characterizations from existing research, the delivered amount of current may be perceived
as mild salty or sour.
Edible Vims may be disguised as decorative gold fakes on food to deliver a tantalizing
surprise to the eater.
We might imagine yet other applications, such as augmenting or restoring eating experiences
for people with taste dysfunction, powering digestible electronics for internal health
monitoring, and allowing for programmable flavors to supplement VR experiences.
Finally, at end of life, Vims easily degrade under backyard, non-industrial conditions
in just a few months.
Over the course of 60 days, a Vim we buried in a garden visibly degraded.
Only 30% of the Vim’s mass remained after 60 days.
Plants near the burial site appeared to remain healthy.
This is unsurprising, since we intentionally selected components that are known to be decomposable.
In fact, our exemplar Vims may be beneficial additions for garden soil health.
Many ingredients in our system, including activated charcoal, graphite, and glycerin,
are known soil conditioners.
Especially with the DIY-friendly nature of our methods, we hope that more makers and
designers can prototype with Vims and discover more recipes, aesthetic possibilities, and
applications for Vims.
Thank you for watching, and please reach out to us if you have any questions.