Tag Archives: capacitive touch sensing

Paper: Pre-Touch Sensing for Mobile Interaction

I have to admit it: I feel as if I’m looking at the sunrise of what may be a whole new way of interacting with mobile devices.

When I think about it, the possibilities bathe my eyes in a golden glow, and the warmth drums against my skin.

And in particular, my latest research peers out across this vivid horizon, to where I see touch — and mobile interaction with touchscreens in particular — evolving in the near future.

As a seasoned researcher, my job (which in reality is some strange admixture of interaction design, innovator, and futurist) is not necessarily to predict the future, but rather to invent it via extrapolation from a sort of visionary present which occupies my waking dreams.

I see things not as they are, but as they could be, through the lens afforded by a (usually optimistic) extrapolation from extant technologies, or those I know are likely to soon become more widely available.

With regards to interaction with touchscreens in particular, it has been clear to me for some time that the ability to sense the fingers as they approach the device — well before contact with the screen itself — is destined to become commonplace on commodity devices.

This is interesting for a number of reasons.

And no, the ability to do goofy gestures above the screen, waving at it frantically (as if it were a fancy-pants towel dispenser in a public restroom) in some dim hope of receiving an affirmative response, is not one of them.

In terms of human capabilities, one obviously cannot touch the screen of a mobile device without approaching it first.

But what often goes unrecognized is that one also must hold the device, typically in the non-preferred hand, as a precursor to touch. Hence, how you hold the device — the pattern of your grip and which hand you hold it in — are additional details of context that are more-or-less wholly ignored by current mobile devices.

So in this new work, my colleagues and I collectively refer to these two precursors of touch — approach and the need to grip the device — as pre-touch.

And it is my staunch belief that the ability to sense such pre-touch information could radically transform the mobile ‘touch’ interfaces that we all have come to take for granted.

You can get a sense of these possibilities, all implemented on a fully functional mobile phone with pre-touch sensing capability, in our demo reel below:

The project received a lot of attention, and coverage from many of the major tech blogs and other media outlets, for example:

  • The Verge (“Microsoft’s hover gestures for Windows phones are magnificent”)
  • SlashGear (“Smartphones next big thing: ‘Pre-Touch’”)
  • Business Insider (“Apple should definitely copy Microsoft’s incredible finger-sensing smartphone technology”)
  • And Fast Company Design (and again in “8 Incredible Prototypes That Show The Future Of Human-Computer Interaction.”)

But I rather liked the take that Silicon Angle offered, which took my concluding statement from the video above:

Taken as a whole, our exploration of pre-touch hints that the evolution of mobile touch may still be in its infancy – with many possibilities, unbounded by the flatland of the touchscreen, yet to explore.

 And then responded as follows:

This is the moon-landing-esque conclusion Microsoft comes to after demonstrating its rather cool pre-touch mobile technology, i.e., a mobile phone that senses what your fingers are about to do.

While this evolution of touch has been coming in the research literature for at least a decade now, what exactly to do with above- and around-screen sensing (especially in a mobile setting) has been far from obvious. And that’s where I think our work on pre-touch sensing techniques for mobile interaction distinguishes itself, and in so doing identifies some very interesting use cases that have never been realized before.

The very best of these new techniques possess a quality that I love, namely that they have a certain surprising obviousness to them:

The techniques seem obvious — but only in retrospect.

And only after you’ve been surprised by the new idea or insight that lurks behind them.

If such an effort is indeed the first hint of a moonshot for touch, well, that’s a legacy for this project that I can live with.

UPDATE: The talk I gave at the CHI 2016 conference on this project is now available. Have a gander if you are so inclined.


Thumb sensed as it hovers over pre-touch mobile phoneKen Hinckley, Seongkook Heo, Michel Pahud, Christian Holz, Hrvoje Benko, Abigail Sellen, Richard Banks, Kenton O’Hara, Gavin Smyth, William Buxton. 2016. Pre-Touch Sensing for Mobile Interaction. In Proceedings of the 2016 CHI Conference on Human Factors in Computing Systems (CHI ’16). ACM, New York, NY, USA, p. 2869-2881. San Jose, CA, May 7-12, 2016. http://dx.doi.org/10.1145/2858036.2858095

[PDF] [Talk slides PPTX] [video – MP4] [30 second preview – MP4] [Watch on YouTube]

Watch Pre-Touch Sensing for Mobile Interaction video on YouTube


Paper: Sensing Tablet Grasp + Micro-mobility for Active Reading

Lately I have been thinking about touch:

In the tablet-computer sense of the word.

To most people, this means the touchscreen. The intentional pokes and swipes and pinching gestures we would use to interact with a display.

But not to me.

Touch goes far beyond that.

Look at people’s natural behavior. When they refer to a book, or pass a document to a collaborator, there are two interesting behaviors that characterize the activity.

What I call the seen but unnoticed:

Simple habits and social cues, there all the time, but which fall below our conscious attention — if they are even noticed at all.

By way of example, let’s say we’re observing someone handle a magazine.

First, the person has to grasp the magazine. Seems obvious, but easy to overlook — and perhaps vital to understand. Although grasp typically doesn’t involve contact of the fingers with the touchscreen, this is a form of ‘touch’ nonetheless, even if it is one that traditionally hasn’t been sensed by computers.

Grasp reveals a lot about the intended use, whether the person might be preparing to pick up the magazine or pass it off, or perhaps settling down for a deep and immersive engagement with the material.

Second, as an inevitable consequence of grasping the magazine, it must move. Again, at first blush this seems obvious. But these movements may be overt, or they may be quite subtle. And to a keen eye — or an astute sensing system — they are a natural consequence of grasp, and indeed are what give grasp its meaning.

In this way, sensing grasp informs the detection of movements.

And, coming full circle, the movements thus detected enrich what we can glean from grasp as well.

Yet, this interplay of grasp and movement has rarely been recognized, much less actively sensed and used to enrich and inform interaction with tablet computers.

And this feeds back into a larger point that I have often found myself trying to make lately, namely that touch is about far more than interaction with the touch-screen alone.

If we want to really understand touch (as well as its future as a technology) then we need to deeply understand these other modalities — grasp and movement, and perhaps many more — and thereby draw out the full naturalness and expressivity of interaction with tablets (and mobile phones, and e-readers, and wearables, and many dreamed-of form-factors perhaps yet to come).

My latest publication looks into all of these questions, particularly as they pertain to reading electronic documents on tablets.

We constructed a tablet (albeit a green metallic beast of one at present) that can detect natural grips along its edges and on the entire back surface of the device. And with a full complement of inertial motion sensors, as well. This image shows the grip-sensing (back) side of our technological monstrosity:

Grip Sensing Tablet Hardware

But this set-up allowed us to explore ways of combining grip and subtle motion (what has sometimes been termed micro-mobility in the literature), resulting in the following techniques (among a number of others):

A Single User ENGAGING with a Single Device

Some of these techniques address the experience of an individual engaging with their own reading material.

For example, you can hold a bookmark with your thumb (much as you can keep your finger on a page in physical book) and then tip the device. This flips back to the page that you’re holding:


This ‘Tip-to-Flip’ interaction  involves both the grip and the movement of the device and results in a fairly natural interaction that builds on a familiar habit from everyday experience with physical documents.

Another one we experimented with was a very subtle interaction that mimics holding a document and angling it up to inspect it more closely. When we sense this, the tablet zooms in slightly on the page, while removing all peripheral distractions such as menu-bars and icons:

Immersive Reading mode through grip sensing

This immerses the reader in the content, rather than the iconographic gewgaws which typically border the screen of an application as if to announce, “This is a computer!”

Multiple Users Collaborating around a Single Device

Another set of techniques we explored looked at how people pass devices to one another.

In everyday experience, passing a paper document to a collaborator is a very natural — and different — form of “sharing,” as compared to the oft-frustrating electronic equivalents we have at our disposal.

Likewise, computers should be able to sense and recognize such gestures in the real world, and use them to bring some of the socially and situationally appropriate sharing that they afford to the world of electronic documents.

We explored one such technique that automatically sets up a guest profile when you hand a tablet (displaying a specific document) to another user:


The other user can then read and mark-up that document, but he is not the beneficiary of a permanent electronic copy of it (as would be the case if you emailed him an attachment), nor is he permitted to navigate to other areas or look at other files on your tablet.

You’ve physically passed him the electronic document, and all he can do is look at it and mark it up with a pen.

Not unlike the semantics — long absent and sorely missed in computing — of a simple a piece of paper.

A Single User Working With Multiple Devices

A final area we looked at considers what happens when people work across multiple tablets.

We already live in a world where people own and use multiple devices, often side-by-side, yet our devices typically have little or no awareness of one another.

But contrast this to the messy state of people’s physical desks, with documents strewn all over. People often place documents side-by-side as a lightweight and informal way of organization, and might dexterously pick one up or hold it at the ready for quick reference when engaged in an intellectually demanding task.

Again, missing from the world of the tablet computer.

But by sensing which tablets you hold, or pick up, our system allows people to quickly refer to and cross-reference content across federations of such devices.

While the “Internet of Things” may be all the rage these days among the avant-garde of computing, such federations remain uncommon and in our view represent the future of a ‘Society of Devices’ that can recognize and interact with one another, all while respecting social mores, not the least of which are the subtle “seen but unnoticed” social cues afforded by grasping, moving, and orienting our devices.


Closing ThoughtS:

An ExpanDED Perspective OF ‘TOUCH’

The examples above represent just a few simple steps. Much more can, and should, be done to fully explore and vet these directions.

But by viewing touch as far more than simple contact of the fingers with a grubby touchscreen — and expanding our view to consider grasp, movement of the device, and perhaps other qualities of the interaction that could be sensed in the future as well — our work hints at a far wider perspective.

A perspective teeming with the possibilities that would be raised by a society of mobile appliances with rich sensing capabilities, potentially leading us to far more natural, more expressive, and more creative ways of engaging in the knowledge work of the future.



Sensing-Tablet-Grasp-Micro-Mobility-UIST-2015-thumbDongwook Yoon, Ken Hinckley, Hrvoje Benko, François Guimbretière, Pourang Irani, Michel Pahud, and Marcel Gavriliu. 2015. Sensing Tablet Grasp + Micro-mobility for Active Reading. In Proceedings of the 28th Annual ACM Symposium on User Interface Software & Technology (UIST ’15). ACM, New York, NY, USA, 477-487. Charlotte, NC, Nov. 8-11, 2015. http://dx.doi.org/10.1145/2807442.2807510
[PDF] [Talk slides PPTX] [video – MP4] [30 second preview – MP4] [Watch on YouTube]

Watch Sensing Tablet Grasp + Micro-mobility for Active Reading video on YouTube

Paper: Sensing Techniques for Tablet+Stylus Interaction (Best Paper Award)

It’s been a busy year, so I’ve been more than a little remiss in posting my Best Paper Award recipient from last year’s User Interface Software & Technology (UIST) symposium.

UIST is a great venue, particularly renowned for publishing cutting-edge innovations in devices, sensors, and hardware.

And software that makes clever uses thereof.

Title slide - sensing techniques for stylus + tablet interaction

Title slide from my talk on this project. We had a lot of help, fortunately. The picture illustrates a typical scenario in pen & tablet interaction — where the user interacts with touch, but the pen is still at the ready, in this case palmed in the user’s fist.

The paper takes two long-standing research themes for me — pen (plus touch) interaction, and interesting new ways to use sensors — and smashes them together to produce the ultimate Frankenstein child of tablet computing:

Stylus prototype augmented with sensors

Microsoft Research’s sensor pen. It’s covered in groovy orange shrink-wrap, too. What could be better than that? (The shrink wrap proved necessary to protect some delicate connections between our grip sensor and the embedded circuitry).

And if you were to unpack this orange-gauntleted beast, here’s what you’d find:

Sensor components inside the pen

Components of the sensor pen, including inertial sensors, a AAAA battery, a Wacom mini pen, and a flexible capacitive substrate that wraps around the barrel of the pen.

But although the end-goal of the project is to explore the new possibilities afforded by sensor technology, in many ways, this paper kneads a well-worn old worry bead for me.

It’s all about the hand.

With little risk of exaggeration you could say that I’ve spent decades studying nothing but the hand. And how the hand is the window to your mind.

Or shall I say hands. How people coordinate their action. How people manipulate objects. How people hold things. How we engage with the world through the haptic sense, how we learn to articulate astoundingly skilled motions through our fingers without even being consciously aware that we’re doing anything at all.

I’ve constantly been staring at hands for over 20 years.

And yet I’m still constantly surprised.

People exhibit all sorts of manual behaviors, tics, and mannerisms, hiding in plain sight, that seemingly inhabit a strange shadow-world — the realm of the seen but unnoticed — because these behaviors are completely obvious yet somehow they still lurk just beneath conscious perception.

Nobody even notices them until some acute observer takes the trouble to point them out.

For example:

Take a behavior as simple as holding a pen in your hand.

You hold the pen to write, of course, but most people also tuck the pen between their fingers to momentarily stow it for later use. Other people do this in a different way, and instead palm the pen, in more of a power grip reminiscent of how you would grab a suitcase handle. Some people even interleave the two behaviors, based on what they are currently doing and whether or not they expect to use the pen again soon:

Tuck and Palm Grips for temporarily stowing a pen

Illustration of tuck grip (left) vs. palm grip (right) methods of stowing the pen when it is temporarily not in use.

This seems very simple and obvious, at least in retrospect. But such behaviors have gone almost completely unnoticed in the literature, much less actively sensed by the tablets and pens that we use — or even leveraged to produce more natural user interfaces that can adapt to exactly how the user is currently handing and using their devices.

If we look deeper into these writing and tucking behaviors alone, a whole set of grips and postures of the hand emerge:

Core Pen Grips

A simple design space of common pen grips and poses (postures of the hand) in pen and touch computing with tablets.

Looking even more deeply, once we have tablets that support a pen as well as full multi-touch, users naturally want to used their bare fingers on the screen in combination with the pen, so we see another range of manual behaviors that we call extension grips based on placing one (or more) fingers on the screen while holding the pen:

Single Finger Extension Grips for Touch Gestures with Pen-in-hand

Much richness in “extension” grips, where touch is used while the pen is still being held, can also be observed. Here we see various single-finger extension grips for the tuck vs. the palm style of stowing the pen.

People also exhibited more ways of using multiple fingers on the touchscreen that I expected:

Multiple Finger Extension Grips for Touch Gestures with Pen-in-hand

Likewise, people extend multiple fingers while holding the pen to pinch or otherwise interact with the touchscreen.

So, it began to dawn on us that there was all this untapped richness in terms of how people hold, manipulate, write on, and extend fingers when using pen and touch on tablets.

And that sensing this could enable some very interesting new possibilities for the user interfaces for stylus + tablet computing.

This is where our custom hardware came in.

On our pen, for example, we can sense subtle motions — using full 3D inertial sensors including accelerometer, gyroscope, and magnetometer — as well as sense how the user grips the pen — this time using a flexible capacitive substrate wrapped around the entire barrel of the pen.

These capabilities then give rise to sensor signals such as the following:

Grip and motion sensors on the stylus
Sensor signals for the pen’s capacitive grip sensor with the writing grip (left) vs. the tuck grip (middle). Exemplar motion signals are shown on the right.

This makes various pen grips and motions stand out quite distinctly, states that we can identify using some simple gesture recognition techniques.

Armed with these capabilities, we explored presenting a number of context-appropriate tools.

As the very simplest example, we can detect when you’re holding the pen in a grip (and posture) that indicates that you’re about to write. Why does this matter? Well, if the touchscreen responds when you plant your meaty palm on it, it causes no end of mischief in a touch-driven user interface. You’ll hit things by accident. Fire off gestures by mistake. Leave little “ink turds” (as we affectionately call them) on the screen if the application responds to touch by leaving an ink trace. But once we can sense it’s your palm, we can go a long ways towards solving these problems with pen-and-touch interaction.

To pull the next little rabbit out of my hat, if you tap the screen with the pen in hand, the pen tools (what else?) pop up:

Pen tools appear

Tools specific to the pen appear when the user taps on the screen with the pen stowed in hand.

But we can take this even further, such as to distinguish bare-handed touches — to support the standard panning and zooming behaviors —  versus a pinch articulated with the pen-in-hand, which in this example brings up a magnifying glass particularly suited to detail work using the pen:

Pen Grip + Motion example: Full canvas zoom vs. Magnifier tool

A pinch multi-touch gesture with the left hand pans and zooms. But a pinch articulated with the pen-in-hand brings up a magnifier tool for doing fine editing work.

Another really fun way to use the sensors — since we can sense the 3D orientation of the pen even when it is away from the screen — is to turn it into a digital airbrush:

Airbrush tool using the sensors

Airbrushing with a pen. Note that the conic section of the resulting “spray” depends on the 3D orientation of the pen — just as it would with a real airbrush.

At any rate, it was a really fun project that garnered a best paper award,  and a fair bit of press coverage (Gizmodo, Engadget, & named FastCo Design’s #2 User Interface innovation of 2014, among other coverage). It’s pretty hard to top that.

Unless maybe we do a lot more with all kinds of cool sensors on the tablet as well.


You might just want to stay tuned here. There’s all kinds of great stuff in the works, as always (grin).

Sensing Pen & Tablet Grip+Motion thumbnailHinckley, K., Pahud, M., Benko, H., Irani, P., Guimbretiere, F., Gavriliu, M., Chen, X., Matulic, F., Buxton, B., Wilson, A., Sensing Techniques for Tablet+Stylus Interaction.  In the 27th ACM Symposium on User Interface Software and Technology (UIST’14)  Honolulu, Hawaii, Oct 5-8, 2014, pp. 605-614. http://dx.doi.org/10.1145/2642918.2647379

Watch Context Sensing Techniques for Tablet+Stylus Interaction video on YouTube

Paper: Writing Handwritten Messages on a Small Touchscreen

Here’s the final of our three papers at the MobileHCI 2013 conference. This was a particularly fun project, spearheaded by my colleague Wolf Kienzle, looking at a clever way to do handwriting input on a touchscreen using just your finger.

In general I’m a fan of using an actual stylus for handwriting, but in the context of mobile there are many “micro” note-taking tasks, akin to scrawling a note to yourself on a post-it, that wouldn’t justify unsheathing a pen even if your device had one.

The very cool thing about this approach is that it allows you to enter overlapping multi-stroke characters using the whole screen, and without resorting to something like Palm’s old Graffiti writing or full-on handwriting recognition.


The interface also incorporates some nice fluid gestures for entering spaces between words, backspacing to delete previous strokes, or transitioning to a freeform drawing mode for inserting little sketches or smiley-faces into your instant messages, as seen above.

This paper also had the distinction of receiving an Honorable Mention Award for best paper at MobileHCI 2013. We’re glad the review committee liked our paper and saw its contributions as noteworthy, as it were (pun definitely intended).

Writing-Small-Touchscreen-thumbKienzle, W., Hinckley, K., Writing Handwritten Messages on a Small Touchscreen. In ACM 15th International Conference on Human-Computer Interaction with Mobile Devices and Services, (MobileHCI 2013), Munich, Germany, Aug. 27-30, 2013, pp. 179-182. Honorable Mention Award (Awarded to top 5% of all papers). [PDF] [video MP4] [Watch on YouTube – coming soon.]

Paper: A Tap and Gesture Hybrid Method for Authenticating Smartphone Users

Tap-Gesture-Authentication-thumbArif, A., Pahud, M., Hinckley, K., Buxton, W., A Tap and Gesture Hybrid Method for Authenticating Smartphone Users (Poster). In ACM 15th International Conference on Human-Computer Interaction with Mobile Devices and Services(MobileHCI 2013), Munich, Germany, Aug. 27-30, 2013, pp. 486-491. [Paper PDF] [Poster Presentation PDF] [Video .WMV] [Video .MP4]

Paper: Motion and Context Sensing Techniques for Pen Computing

I continue to believe that stylus input — annotations, sketches, mark-up, and gestures — will be an important aspect of interaction with slate computers in the future, particularly when used effectively and convincingly with multi-modal pen+touch input. It also seems that every couple of years I stumble across an interesting new use or set of techniques for motion sensors, and this year proved to be no exception.

Thus, it should come as no surprise that my latest project has continued to push in this direction, exploring the possibilities for pen interaction when the physical stylus itself is augmented with inertial sensors including three-axis accelerometers, gyros, and magnetometers.


In recent years such sensors have become integrated with all manner of gadgets, including smart phones and tablets, and it is increasingly common for microprocessors to include such sensors directly on the die. Hence in my view of the world, we are just at the cusp of sensor-rich stylus devices becoming  commercially feasible, so it is only natural to consider how such sensors afford new interactions, gestures, or context-sensing techniques when integrated directly with an active (powered) stylus on pen-operated devices.

In collaboration with Xiang ‘Anthony’ Chen and Hrvoje Benko I recently published a paper exploring motion-sensing capabilities for electronic styluses, which takes a first look at some techniques for such a device. With some timely help from Tom Blank’s brilliant devices team at Microsoft Research, we built a custom stylus — fully wireless and powered by an AAAA battery — that integrates these sensors.

These range from very simple but clever things such as reminding the user if they have left behind the pen — a common problem that users encounter with pen-based devices — to fun new techniques that emulate physical media, such as the gesture of striking a loaded brush on one’s finger in water media.


Check out the video below for an overview of these and some of the other techniques we have come up with so far, or read more about it in the technical paper linked below.

We are continuing to work in this area, and have lots more ideas that go beyond what we were able to accomplish in this first stage of the project, so stay tuned for future developments along these lines.

Motion-Context-Pen-thumbHinckley, K., Chen, X., and Benko, H., Motion and Context Sensing Techniques for Pen
In Proc. Graphics Interface 2013 (GI’13).  Canadian Information Processing Society, Toronto, Ont., CanadaRegina, Saskatchewan, Canada, May 29-31, 2013. [PDF] [video – MP4].

Watch Motion and Context Sensing Techniques for Pen Computing video on YouTube

Paper: Enhancing Naturalness of Pen-and-Tablet Drawing through Context Sensing

Context-Sensing Pen with multi-touch and orientation sensorsSun, M. Cao, X., Song, H., Izadi, S., Benko, H., Guimbretiere, F., Ren, X., and Hinckley, K. Enhancing Naturalness of Pen-and-Tablet Drawing through Context Sensing.  In Proc. ACM International Conference on Interactive Tabletops and Surfaces (ITS ’11). ACM, New York, NY, USA,  Kobe, Japan, November 13-16, 2011, pp. 212-221. [PDF] [video – WMV].

Watch Enhancing Naturalness of Pen through Context Sensing video on YouTube