Hello everyone,
I am Purnendu, a Ph.D. student at the ATLAS Institute, University of Colorado, Boulder.
I am here to present the work “Electriflow: Soft Electrohydraulic
Building Blocks for Prototyping Shape-changing Interfaces”.
This work is done in collaboration with my co-authors Sasha M Novack, Eric Acome,
Christoph Keplinger, Mirela Alistar, Mark D Gross, Carson Bruns, and Daniel Leithinger.
We propose a new prototyping technology for shape-changing interfaces.
Electrohydraulic mechanisms are ubiquitous in the biological world.
Nature prefers electrohydraulic phenomena to drive shape change.
For example, plants like Venus Flytrap catch their prey through leaf closure
employing electrohydraulic forces.
The drastic shape transformation in certain species
of octopus is a result of electrohydraulic phenomena.
A pufferfish threatens a predator by filling its elastic stomach with fluid
also under electrohydraulic effects .
Electrohydraulic processes drive shape change in plants and animals,
and augment their ability to communicate and interact.
In the field of Human-Computer Interaction, taking inspiration
from the natural world, Bio-inspired Shape-changing Interfaces have been proposed.
Traditionally they are constructed out of soft prototyping techniques
which generallyrely on pneumatics, humidity, or heat for actuation.
But they also suffer from limitations like being bulky in terms of the control system
and slow in shape transformation.
In this work, we present electrohydraulic actuators as building blocks
for prototyping shape-changing interfaces.
These compliant actuators generate an immediate hydraulic force
upon electrostatic activation without an external fluid supply source.
They are silent and fast in operation and can be fabricated with
commodity materials.
Here, we present the general design of these actuators.
It consists of
oil-filled flexible plastic pouches partially covered with
flexible electrodes on both sides as shown in Figure B(i).
When a DC voltage of the order of 8kV is applied across the pair of
flexible electrodes, they tend to zip together, shown in figure B(ii).
This zipping motion of the electrodes displaces the fluid between them
to the surrounding volume resulting in shape change, as in figure B (iii).
These pouches are further attached with strain limiting layers
to create sharp hinge-like bends.
A thin insulating layer between the electrodes and the strain limiting layer
is necessary for failure-free operation of the actuators, shown in Figure A.
These actuators can come in a variety of geometries.
We propose the design of
three such novel actuators: The Hinge Bending, the Crescent, and the Quarter Moon.
Here, we show the actuator geometries along with their shape transformations.
We also present a design tool to aid the design and fabrication of these actuators.
A user can load the predefined actuator geometry and adjust the parameters according to their
needs.
Afterward, the tool allows the user to visualize the shape change and export fabrication
files.
These actuators can be fabricated with commodity materials and easily available tools.
We begin by heat sealing two pieces of polymer sheet using a custom modified heat of a CNC
machine
to create the outer geometry of the pouch.
We leave a small input port for oil filling.
Afterward, we manually fill the pouch with silicone oil using syringes and seal the input
port.
We then paint the flexible electrodes using conductive carbon paint and eventually,
trim the excess polymer sheet.
Here, we show the DC power supply used to activate these actuators powered by a lithium
polymer battery
similar to the ones used in smartphones these days.
Though the activation voltage is of the order of kilovolts, this power supply ensures
very low current consumption making these actuators human safe.
Here, the bending angle is plotted against applied voltage for each of the actuator types.
A Crescent actuator can produce a smooth organic bend with a maximal bending angle of around
sixty (60) degrees
while the Quarter Moon actuator produces sharp bends with a bending angle of around forty
(40) degrees .
Butterflies are fascinating organisms given their ability to rapidly actuate their wings.
The typical butterfly wings can actuate at a frequency of around 10 Hz but for certain
species of moths,
it can go up to 26.1 Hz.
Electroflow actuators can be a great prototyping technology for the design of a bioinspired
butterfly soft robot
given their compact design and high frequency of actuation.
Here, we show an example prototype of a butterfly,
composed of two Crescent actuators embedded in the wings that can actuate up to a frequency
of 25 Hz.
The compact design of Crescent actuators ensures they can be embedded on thin-film sheets
for character animation . Here, each of the ears has an actuator underneath.
Crescent Actuators can be combined in a wide variety of numbers and configurations, depending
upon the need
of prototyping.
For example, a group of crescent actuators forms the basis of a flower that blooms
Flexible displays enable new opportunities for interaction with mobile devices.
To explore a thin form factor flexible display, we prototyped a shape-changing mockup with
an embedded
bending quarter moon actuator (see figure 15).
The quarter moon actuator ensures a sharp bend for the display,
without needing a strain limiting layer.
We hope in the future, Electriflow may act as the basis
for actuating such a flexible display.
These actuators can bend like a hinge and actuate light as well as heavy objects.
For the
Hinge-bending actuator the maximum weight lifted without reduction in bending angle
was 13 grams.
Here we show two example prototypes as an actuating box and an actuating origami bird.
To summarize, we presented Electriflow: a novel prototyping technology for shape changing
interfaces.
These actuators offer novel features like :
Compact Design, Rapid actuation, Silent Operation, and Easy Fabrication
The compactness, immediate actuation and silent operation of these mechanisms enrich
the library of prototyping technologies for shape changing interfaces
During the process of developing this work, we also realized a number of limitations
that open up possibilities for future work, like
We realize the need for the user evaluation of the prototypes
This work primarily focused on prototyping the output of shape-changing interfaces and
less on sensing user input.
Adding input sensing modalities such as embedded touch sensing would greatly increase the interactive
capabilities.
We also think this work opens up possibilities for other new kinds of soft electrohydraulic
actuator geometries
with novel functions
There is also a possibility of adding a simulation feature in the software tool as well as lowering
the voltage of activation by choosing better materials as well as insulating the electrodes.
Thank you so much for being here and listening to this work.
I will be happy to take questions