hello my name is Craig Shultz and I'm presenting flat panel haptics
embedded Electroosmotic pumps for scalable shape displays this work was done during
my post talk with Chris Harrison at the future interfaces group at Carnegie Mellon
reprogrammable shape-shifting computer interfaces have captured our Collective
imagination for decades here's a clip from the original X-Men movie showing a general
purpose two and a half d shaped display it's made up of hundreds or even thousands
of programmable pixels which spring to life and animate Our Heroes master plan
this Vision has not just been limited to the movies however as there's also
a long history of researchers building various shape-shifting and fingertip display interfaces
on the surface these approaches are great even with only tens of actuators you can start to see
a glimmer of an ultimate haptic display or as one researcher called it the holy Braille of haptics
but there's one major problem with the previous approaches
they simply don't scale if you want to build high resolution general purpose displays
these Technologies need to be miniaturized so that they can scale up this is where our work comes in
our main contribution is to provide a vision and demonstration of miniaturizable scalable
shape displays at the outset we asked ourselves if current shape displays are sort of like a CRT
monitor which are effective but overall expensive complicated and bulky could we envision and build
a flat panel haptic shape display something that's more like a modern LCD cheaper simpler and slimmer
what I came up with is a new approach and what I call a flat panel haptic display
here's a video of one of our systems shown in real time rows of bumps are emerging from the
surface Under Computer control note that the whole stack up here is under five millimeters thick
I fabricated this device from scratch after quite a long process of iteration it's got a
stretchy elasma surface that's actuated by an array of individually controlled pumps what's
causing the shape change here is pressurized fluid inflating and deflating each output pixel
the hydraulic system is entirely self-contained powered and controlled only by an electrical cable
it's lightweight in this case under 40 grams
enabling this small of a form factor is a new actuation technique I call
embedded Electro osmotic pumps or eeops
here's the schematic of how these work each pump
pulls fluid from a common Reservoir and pressurizes the output elastomer layer
on the right you're seeing this process happen repeatedly with the Prototype note that the
pump active layer is only about a quarter of a millimeter thick it's actually embedded in the
device itself I'm going to put an error on it just to point out how small it really is
if you take a cross section of just the pump this is what it looks like under a microscope I can
apply an input voltage across the two electrodes and almost like magic fluid flows in the system
going back to the idea of coming up with a flat panel haptic display it should be noted that
this configuration is in fact very similar to the principle Liquid Crystal displays or LCDs that is
liquid Crystal layer either blocks or allows light from a backlight to pass through depending on the
applied voltage this type of approach of embedding the active element directly into a surface is
how you get the thinness and large numbers of elements you need for really large pixel densities
so how does this work please read our paper for more information but here's our quick primer
these pumps use an electric connected effect known as electrosmotic flow and
fluid at rest charged species of ions are uniformly distributed as seen here
but when you bring a solid into the liquid a non-uniform surface charge
builds up to the interface this is called the electrical double layer
so now you have an accumulated charge density in the fluid just outside the solid surface and
is free to move in the liquid so how do you get charged to move well you put an electric field
so if I take some external electrodes and apply a voltage to them the charges will begin to slide
the mobile charges then viscously couple to the rest of the fluid and what was originally is
just a surface flow becomes a bulk flow voila you have direct voltage to flow transduction
I'll briefly mention the pump's main construction components as this is another key aspect of this
approach I used all off the shelf easily attainable materials silicone glass fiber
pet common sheet adhesives and in the middle there's a PCB this PCB is critical to the
mentorization process as the modern Precision of commodity PCB lithography and CNC drilling enables
complex electric patterning and practical system routing at almost negligible cost
all of these wooden materials were ordered or processed in house and then assembled in
layers the entire Stack Up was designed with the idea of scalability in mind
whether you're building one actuator 50 or 100 the process is really not all that different
it characterize the pump's performance with a series of physical tests
I built pumps of various sizes ranging from two millimeters to 10 millimeters in diameter
as seen here these pumps in two conditions a block pressure condition and an open Flow condition this
is similar to the stall torque and no load velocity characterization of electric motor
here's an example plot of open Flow you can see how flow is directly proportional
to the applied electric field note that the float also goes both positive and negative
as this effect is sensitive to voltage polarity and is completely bi-directional
results from tests across all different pump sizes for a range of different voltages
you can see that both flow and pressure are relatively linear can increase with voltage flow
is proportional to pump area while pressure is independent of public area as predicted by Theory
if I plot one of our eeops here in red against a wide variety of other micro
pumps you can see that we have achieved one of the smallest pump volumes and highest
volume normalized flow rates ever shown in the literature this means that these pumps
are an incredibly small and can move large amounts of fluid for their size
pump displacement by pushing up against the Piston connected to a displacement measurement device you
can see the displacement scales with pump diameter and rapidly increases before reaching a maximum
using the same piston I applied different weight loads and measure the force capability
an average output layer can push up against at least
100 grams of force about the typical interaction Force coming from a user
I also tested some of these devices directly with users
using four millimeter and eight millimeter diameter actuators I applied pulsing waveforms at
three different time scales a quarter of a Hertz one Hertz and 10 Hertz and users rested their
finger on top of each device and reported whether they could feel or not feel a certain stimuli
results from this absolute detection threshold experiment showed that all
the users could feel the stimuli at Peak voltages below 200 volts
a few example applications that showcase the potential of flat panel haptic displays
general purpose shape displays can take on a variety of surface
patterns like these textures numbers icons or even UI elements or emojis
you need a control panel which can offer Dynamic tactile portices and more complex
shaped geometries so I was able to take an off-the-shelf flexible OLED the kind that
are in today's holding smartphones and actuate it from Below what result is now a deformable
visual display with icons like this setting button which can animate to show notification
button which slowly breathes in and out until I click it to dismiss it
this technique can also give us back the tactile keyboards that we lost
when you made the transition to touch screens here's a keyboard popping up under my finger
I'm also showing it with the screen off here for better clarity
include in this work I introduced my vision for flat panel haptic shape displays
I built and characterized device stack UPS based on embedded Electro osmotic pumps or eeops
these devices are under five millimeters in thickness with a quarter millimeter
thick active layer yet they can still generate plus or minus 50 kilopascals of
pressure and this can be used to inflate hydraulic actuators in under one second
these initial prototypes were detectable by users with under 200 volts applied
finally I showcase three different sample applications a general purpose display
a pop-up interface and a flexible OLED touchscreen please see our paper for more details