Prodromou’s Weblog

Just another weblog

TFS: Tablet Fingertip Syndrome

Tablet Fingertip Syndrome


Tablet computers have become very popular with the iPad and Androids from a dozen or more manufacturers. These devices center on a graphical user interface with the user’s fingertip gestures providing the commands and navigation.


The primary user interactions are the ‘tap’ and ‘slide’ or ‘swipe’ gestures. These are almost exclusively applied to the top surface of the tablet which senses the user commands through a capacitive glass sensor that is mounted atop the display. Tablet computer displays and capacitive sensors range in size from 6 to 10 inches (diagonal measurement).


The same touch gestures and input device configurations are used in hundreds of millions of smartphones, including the iPhone series, Motorola’s Droids and dozens of other Android-based mobile phones from numerous manufacturers. The display size on these devices ranges from approximately 3.5 inches to 5 inches.


I am an early adopter and have been using a Samsung Android Tablet for over 6 months now. I have noticed that after using the tablet for extended periods of time (two hours or more) my index fingertip becomes sensitive – not sore or exceedingly painful, but definitely sensitive. So much so that I begin to swipe the tablet with the side of my fingertip to avoid aggravating the sensitive tip. Tapping appears to be far less injurious to the fingertip than sliding or swiping.


Why should this happen? ‘As smooth as glass’ is an oft used expression in our everyday language. Yet, excessive swiping of the same fingertip over a very smooth glass surface can cause discomfort to the user.


Glass is indeed smooth on a macroscopic scale, but not so smooth on a microscopic scale, as can be seen in the Atomic Force Microscope image below (Figure 1).



Figure 1: Atomic Force Micrograph of a 20×20 micron glass surface (from Wikipedia article on Atomic Force Microscopy


The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, made of about 75% silica (SiO2) plus Na2O, CaO, and several minor additives. Glass is quite hard, measuring 5.5 on the Mohs scale, the same as a knife blade. (The Mohs scale ranges from 1.0 for talc to 10 for diamond). The abrupt sharp silicate edges in the glass are like shards of glass that one finds when a drinking glass is shattered on concrete. A large array of such shards on the surface of a smooth glass tablet display have similar cutting properties to sandpaper.


Sandpaper is graded by a grit factor, based on the size of the silica particles on the surface of the paper. So-called “superfine” sandpaper (rated 500 grit) uses particles averaging 20 microns in diameter. Ultra Fine sandpaper (1000 grit) uses particles approximately 10 microns in diameter. As can be seen from the Figure 1, smooth glass has ridges and edges of with feature sizes of approximately 0.1 micron. If we were to think of “smooth” glass as Super-Ultra Fine sandpaper, it would equate to 100,000 Grit, with average silicate particles of 0.1 microns in feature size.


So much for the hardness and sandpaper roughness of smooth glass. But surely the amount of sliding and swiping of a fingertip across its surface is pretty minimal, one is tempted to think. The range of a typical swipe across a tablet computer or smartphone screen is only an inch or two. This motion is repeated hundreds or thousands of times per hour of use. That can add up.


How far does a fingertip travel across the glass sensor surface of a smartphone or tablet? It depends on the activity and the display size of the device. For example, reading e-mails or searching through tabular lists frequently involves a sliding motion up and down the display page as each segment of the document is read by the user. For a typical use-case of reading, say, 20 e-mails, with an average of four displays per e-mail document, the user’s fingertip may slide across 320 inches of glass on a 4” smartphone or 800 inches on a 10” tablet. This task may typically be done in less than 30 minutes. In another use case, a game of Angry Birds requires about 4-5 slingshot slides, of about 1-2 inches plus 3-5 full-screen screen swipes per level. For a typical game of 30 levels in 30 minutes (including level replays) the finger might slide across 660 inches on a 4-inch smartphone screen or 1080 inches on a 10-inch tablet screen.


Let’s make the assumption that these 2 activities represent a typical daily usage, then the user’s forefinger will rub across 80+ feet of glass on a 4” smartphone or 150+ feet on a 10” tablet! You could therefore swipe a mile or more of 100,000 Grit sandpaper on your tablet of smartphone every month. That can certainly explain the onset of what I am calling “Tablet Fingertip Syndrome” or TFS.


It is not likely that tablet computers or smartphones will disappear in the near future. After all, keyboards did not go away when we recognized their uncomfortable or painful effects on users’ wrists (carpal tunnel syndrome). But can anything be done to head off or alleviate a potential TFS epidemic?


Here are a few possibilities:


  1. Manufacturers can specify glass that has fewer or smaller microscopic variations/edges.
  2. Manufacturers can coat the touch surface with a softer material or a lubricant to reduce the sandpaper effect on the users fingertip.
  3. Manufacturers can incorporate other types of user interface devices such as trackballs for use with most common navigation functions. The first Android smartphone, the G1 by HTC included a mini-trackball.
  4. New sensor technologies can be developed that do not require actual touching. For example, optical sensing can determine the location, tapping or “pressure” of the user’s fingertip without the need to actually touch the glass surface.
  5. Software developers can define alternative gestures for navigation that require less (or no) fingertip travel across the glass surface. Perhaps joystick style taps or ‘page up” and “page down” buttons that eliminate the need for full page swipes.
  6. Fingertip protection that can be worn without impeding the utility of the tablet or smartphone.

This paper has been written to expose the potential for more widespread user injuries as tablets and smartphones become more prevalent. Now is the time for manufacturers and developers to devise better user interfaces and experiences.

June 16, 2011



June 16, 2011 Posted by | Uncategorized | 1 Comment

Spanakopita (Greek Spinach Pie)

Yaya’s Spanakopita (Greek Spinach Pie)

Prep Time: 45 Min
Cook Time: 30-40 min
Ready In: 1 Hr 15+ Min
Yield 12 servings, 3×3 inches each

Required Utensils
9×12 inch baking pan
Large (12 in.) skillet
Medium (4 qt.) mixing bowl
Small (8 oz.) bowl


3 tablespoons olive oil
1 large onion, chopped (about 1/4 in.)
6 stalks green onions, chopped
3 cloves garlic, minced
2 10-oz packages frozen cooked/chopped spinach (thawed, drained)
1/2 cup chopped fresh parsley
2 eggs, lightly beaten
1/2 cup ricotta cheese (or Greek yoghurt)
1 cup crumbled Greek feta cheese
12 sheets 9×12 phyllo dough
1/3 cup pine nuts
1/2 tsp Allspice
1 tsp salt
1/4 cup olive oil (for brusing pan & phyllo dough)


1.  Preheat oven to 350 degrees F.
2.  Heat 3 tablespoons olive oil in a large skillet over medium heat. Saute chopped onion, green onions and garlic, until the onions are soft and lightly browned.
3.  Stir in spinach and parsley for about 2 minutes. Remove from heat and set aside to cool.
4.  In a medium bowl, mix together eggs, ricotta or yoghurt, and feta. Sprinkle salt and allspice over the mixture, then stir in pine nuts and cooled spinach/onion mixture. Fold until ingredients are well mixed.
5. Lightly oil a 9×12 inch baking pan. Lay 1 sheet of phyllo dough in the baking pan, and brush lightly with olive oil. Lay another sheet of phyllo dough on top, brush with olive oil, and repeat process with two more sheets of phyllo (4 sheets total).
6. Spread half of the spinach and cheese mixture into pan.
7. Layer 4 more sheets of phyllo dough, brushing each with olive oil. Then evenly spread remainder of spinach and cheese mixture.
8. Layer the last 4 sheets of phyllo dough, brushing each with oil. Tuck overhanging dough into pan to seal filling.
9. Bake in the preheated oven for 30 to 40 minutes, until light golden brown. Cut into 3-inch squares and serve while hot.

Pappou’s alternative preparation:

Beginning in step 5, lightly oil 2 flat cookie sheets. Then fill and fold phyllo dough into 12 triangle-shaped individual spinach “pockets”. Brush top of each triangle with olive oil. Place on cookie sheets and bake for 30 minutes.

To form each triangle “pocket”, first fold the phyllo sheet in half (to 6×9 inches) and brush the top side with olive oil. Place about 4 Tbsp of spinach/cheese mixture in the middle of the folded sheet. Bring top left corner down on 45 degree angle to bottom center and repeat with top right corner. Now fold bottom 1-inch flap up to seal the pocket, brushing again with olive oil. Place on cookie sheet with folded side down. Brush the top with olive oil.

June 13, 2011 Posted by | Uncategorized | Leave a comment

My first Amazon review: Beethoven’s 5 Piano Concerti by Claudio Arrau

FrontThis 3-CD set includes all 5 piano concerti of Ludwig Van Beethoven, a singularly distinguished composer during the transition from the Classical to the Romantic eras. Deservedly, he is acknowledged as one of the most influential composers of all time in Western classical music.

The piano concerti are an important component of his orchestral portfolio.

The tracks in this set include:
Piano Concerto No. 1 in C major, op. 15:
I. Allegro con brio
II. Largo
III. Rondo. Allegro scherzando
Piano Concerto N°2 in B Flat major, Op 19:
I. Allegro con brio
II. Adagio
III. Rondo. Molto allegro
Piano Concerto No. 3 in C minor, Op. 37
I. Allegro con brio
II. Largo
III. Rondo. Allegro
Piano Concerto No. 4 in G major, op. 58
I. Allegro moderato (G major)
II. Andante con moto (E minor)
III. Rondo (Vivace) (G major)
Piano Concerto No. 5 in E-flat major, Op. 73 “The Emperor Concerto”
I. Allegro (E flat major)
II. Adagio un poco mosso (B major)
III. Rondo: Allegro ma non troppo (E flat major)

Claudio Arrau León (1903-91) a Chilean pianist, universally deemed as one of the greatest pianists of the 20th century, is particularly recognized for his interpretations of Beethoven’s music. His style is often characterized by the rich, weighty tone that graces these interpretations in a distinctive & well-rounded voice In these performances, Mr. Arrau is accompanied by the Sächsische Staatskapelle Dresden under the direction of Sir Colin Davis.

September 28, 2009 Posted by | Uncategorized | 1 Comment

My World Famous Hummus Recipe

I have been requested to pass on my world-famous hummus recipe and I am happy to oblige. However, I should warn you that this recipe makes a huge batch of hummus (serves at least 18 people) and it doesn’t scale well because of the tahini. I should also tell you that this recipe only works well if you use a Cuisinart (not a blender). Finally, the process and order is important.

World Famous Hummus

6 15 oz. cans of chick peas (garbanzo beans)
1 15 oz can of Tahini (I have found the Joyva brand to taste the best)
1 cup lemon juice (if you want to squeeze fresh lemons, you can. Squeeze until you get 1 cup of juice)
1 tablespoon of ground cumin (you can go up to 2T if you like it spicier/smokier in flavor)
8-12 cloves of garlic, whole, peeled
2 tablespoons of salt
1/2-1 tsp paprika
1/4 cup extra virgin olive oil
Parsley, cucumber, tomato, green pepper (optional)

When you open the cans of garbanzo beans, drain 3 of them completely and leave the other 3 in their juice (this will get the right consistency). I always reserve the juice from one can to adjust the thickness of the puree mixture. Use the cans in pairs, one drained and one not. Clean the cloves of garlic of their skin and cut off the dried hard ends. Pour the first pair of cans of garbanzo beans in the cuisinart, and add the lemon juice, cumin, salt and cloves of garlic. Puree in the cusinart until silky smooth (the smoother, the better). The process that seems to work best is to pulse the cuisinart on and off in the beginning until the mixture flows smoothly, then let the cuisinart run for several minutes and observe the smoothness of the chick pea puree. Remove the pureed mixture into a large (8 quart ?) stainless steel mixing bowl. Be sure to clean it out well because the lemon juice hardens the tahini in the next step. Next, pour another pair of garbanzo bean cans in the cuisinart, and add the entire can of tahini. I find it works best to open the bottom of the tahini can, because the sesame paste settles to the bottom and it is hard to scrape it all out if you open the top end. If you use a partial can of tahini, you can’t be sure your got the right ratio of sesame oil to sesame paste. Again, use the pulse-then-let-run process until it is very smooth. If you find the puree mixture is too thick and is balling up, add some of the reserved garbanzo juice through the top of the cuisinart until it flows smoothly. Once again, empty all of the contents of the cuisinart into the mixing bowl. The third pair of cans is pureed without adding anything else, and this helps clean out the cuisinart of all the tahini, spices, etc from the earlier steps. Add the last of the pureed chick peas to the mixing bowl when it is very smooth.

Now fold and mix your hummus in the mixing bowl until it is homogeneous. Transfer everything into your serving dish. Smooth the top surface and sprinkle it with the paprika. Float the olive oil on top of everything. Garnish with finely chopped parsley and/or cut up cucumbers, tomatoes or green peppers. Serve with cut-up pita bread or vegetable crudite.

This hummus will freeze well if you want to save some for future use. Preferably, do not add the olive oil to the portions you freeze until you thaw it out and are ready to serve it.

The secret to this recipe is to puree it until it is VERY smooth. “Gritty hummus does not taste as good as smooth hummus“. This is a life lesson. Print it up in an old English font, on parchment paper, and hang it in a picture frame in your kitchen.

November 26, 2008 Posted by | Recipes | | 2 Comments