Zac Vawter for The Wall Street Journal

Zac Vawter has his bionic leg fitted with the help of Elizabeth Halsne, Certified Prosthetist, at the Rehabilitation Institute of Chicago on Tuesday, Sept. 24, 2013, in Chicago, Ill. Vawter has been successfully using the experimental thought-controlled bionic leg which allows him to walk, climb stairs, and move the leg while seated. Andrew A. Nelles for The Wall Street Journal

Zac Vawter walks down stairs with his bionic leg at the Rehabilitation Institute of Chicago on Tuesday, Sept. 24, 2013, in Chicago, Ill. Andrew A. Nelles for The Wall Street Journal

Zac Vawter walks up stairs with his bionic leg at the Rehabilitation Institute of Chicago on Tuesday, Sept. 24, 2013, in Chicago, Ill. Andrew A. Nelles for The Wall Street Journal

Zac Vawter walks down a ramp as Kim Ingraham, left, Research Engineer, and Dr. Levi Hargrove, center, observe at the Rehabilitation Institute of Chicago on Tuesday, Sept. 24, 2013, in Chicago, Ill. Andrew A. Nelles for The Wall Street Journal

Zac Vawter lifts his bionic leg as Dr. Levi Hargrove, right, observes at the Rehabilitation Institute of Chicago on Tuesday, Sept. 24, 2013, in Chicago, Ill. Andrew A. Nelles for The Wall Street Journal

Adjustments are made to Zac Vawter's bionic leg at the Rehabilitation Institute of Chicago on Tuesday, Sept. 24, 2013, in Chicago, Ill. Andrew A. Nelles for The Wall Street Journal

Zac Vawter walks down a hallway as Elizabeth Halsne, right, Certified Prosthetist, observes at the Rehabilitation Institute of Chicago on Tuesday, Sept. 24, 2013, in Chicago, Ill. Andrew A. Nelles for The Wall Street Journal

Dr. Levi Hargrove, right, speaks with Zac Vawter, left, while testing his bionic leg at the Rehabilitation Institute of Chicago on Tuesday, Sept. 24, 2013, in Chicago, Ill. Andrew A. Nelles for The Wall Street Journal

Dorothy Coyle for Crain's Chicago Business

Dorothy Coyle at Coyle & Herr in Chicago, Ill., on Tuesday, August 13, 2013. Dorothy Coyle was director of the Chicago Office of Tourism when Crain's named her a 40 Under 40 in 2006. Today, she's running Coyle & Herr furniture consignment center at the Bridgeport Arts Center. (Andrew A. Nelles for Crain's Chicago Business)

Sports for the Associated Press and Chicago Tribune

A fan talks on his cellphone as the Chicago White Sox play the Toronto Blue Jays in a baseball game on Monday, Sept. 23, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Toronto Blue Jays' J.P. Arencibia celebrates hitting a home run against the Chicago White Sox during the fifth inning of a baseball game on Monday, Sept. 23, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Toronto Blue Jays' J.P. Arencibia reacts to striking out against the Chicago White Sox during the seventh inning of a baseball game on Monday, Sept. 23, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Toronto Blue Jays shortstop Ryan Goins fields a ground ball hit by the Chicago White Sox's Paul Konerko during the fourth inning of a baseball game on Monday, Sept. 23, 2013, in Chicago. Konerko was out at first base. (AP Photo/Andrew A. Nelles)

Toronto Blue Jays center fielder Anthony Gose comes up short of a catch on a single hit by the Chicago White Sox's Alejandro De Aza during the second inning of a baseball game on Monday, Sept. 23, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Chicago White Sox's Dayan Viciedo, left, celebrates with Marcus Semien, right, after Viciedo scored on Semien's home run against the Toronto Blue Jays during the second inning of a baseball game on Monday, Sept. 23, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Chicago White Sox's Paul Konerko hits a single against the Toronto Blue Jays during the first inning of a baseball game on Monday, Sept. 23, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Atlanta Braves' B.J. Upton reacts to being called out at first base on a dropped third strike, ending their 3-1 loss to the Chicago Cubs in a baseball game on Saturday, Sept. 21, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Chicago Cubs catcher Dioner Navarro throws to first base after a dropped third strike for an out against the Atlanta Braves' B.J. Upton, ending the Cub's 3-1 victory in a baseball game on Saturday, Sept. 21, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Chicago Cubs' Anthony Rizzo celebrates with Nate Schierholtz after Rizzo scored on Schierholtz's sacrifice fly against the Atlanta Braves during the eighth inning of a baseball game on Saturday, Sept. 21, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Atlanta Braves' Kris Medlen bunts against the Chicago Cubs during the seventh inning of a baseball game on Saturday, Sept. 21, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Atlanta Braves' Chris Johnson watches as he hits a ball that was caught for an out in deep right field against the Chicago Cubs during the sixth inning of a baseball game on Saturday, Sept. 21, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Chicago Cubs' Luis Valbuena reacts to hitting a double against the Atlanta Braves during the third inning of a baseball game on Saturday, Sept. 21, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Chicago Cubs right fielder Nate Schierholtz catches a fly ball hit by the Atlanta Braves' Andrelton Simmons during the third inning of a baseball game on Saturday, Sept. 21, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Atlanta Braves' Gerald Laird reacts to striking out against the Chicago Cubs during the second inning of a baseball game on Saturday, Sept. 21, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Atlanta Braves starting pitcher Kris Medlen pitches against the Chicago Cubs during the first inning of a baseball game on Saturday, Sept. 21, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Dunbar's Demoria Harris (2) is taken down by Curie's Mike Goldsmith (16) during the fourth quarter at Lane Stadium in Chicago, Ill., on Friday, September 20, 2013. (Andrew A. Nelles/ For The Chicago Tribune)

Curie's Jerome Thomas (10) is taken down by Dunbar's Jason Dawson (10,) left, during the second quarter at Lane Stadium in Chicago, Ill., on Friday, September 20, 2013. (Andrew A. Nelles/ For The Chicago Tribune)

Dunbar's Jayton Dorsey (7) bolts past Curie's Andre Green (5) during the first quarter at Lane Stadium in Chicago, Ill., on Friday, September 20, 2013. (Andrew A. Nelles/ For The Chicago Tribune)

Curie's Allondre Pickens (1) prepares for a hit from Dunbar's Jayton Dorsey (7) during the first quarter at Lane Stadium in Chicago, Ill., on Friday, September 20, 2013. (Andrew A. Nelles/ For The Chicago Tribune)

Lots of baseball

Chicago White Sox right fielder Jordan Danks catches a fly ball hit by the Minnesota Twins' Trevor Plouffe during the fifth inning of a baseball game on Tuesday, Sept. 17, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Chicago White Sox's Dayan Viciedo reacts to swinging on a strike against the Detroit Tigers during the fourth inning of a baseball game on Tuesday, Sept. 10, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Chicago White Sox right fielder Avisail Garcia catches a fly ball hit by the Detroit Tigers' Don Kelly during the first inning of a baseball game on Tuesday, Sept. 10, 2013, in Chicago, Ill. (AP Photo/Andrew A. Nelles)

Detroit Tigers left fielder Andy Dirks catches a fly ball hit by the Chicago White Sox's Adam Dunn during the sixth inning of a baseball game on Tuesday, Sept. 10, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Detroit Tigers catcher Alex Avila and starting pitcher Rick Porcello hug after they defeated the Chicago White Sox 9-1 in a baseball game on Tuesday, Sept. 10, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Rain falls on U.S. Cellular Field as fans wait for the baseball game between the Cleveland Indians and the Chicago White Sox to begin on Sunday, Sept. 15, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Cleveland Indians second baseman Jose Ramirez fields the ball as the Chicago White Sox's Alexei Ramirez grounded out during the first inning of a baseball game on Sunday, Sept. 15, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Cleveland Indians' Jose Ramirez reacts as he strikes out swinging against the Chicago White Sox during the third inning of a baseball game on Sunday, Sept. 15, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Cleveland Indians' Asdrubal Cabrera, right, celebrates with teammate Carlos Santana after hitting a home run against the Chicago White Sox during the sixth inning of a baseball game on Sunday, Sept. 15, 2013, in Chicago. Santana scored on Cabrera's home run. (AP Photo/Andrew A. Nelles)

Chicago White Sox's Alexei Ramirez reacts after striking out swinging against the Cleveland Indians during the sixth inning of a baseball game on Sunday, Sept. 15, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Cleveland Indians center fielder Drew Stubbs loses a ball hit by the Chicago White Sox's Josh Phegley during the seventh inning of a baseball game on Sunday, Sept. 15, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Chicago White Sox second baseman Gordon Beckham forces out the Minnesota Twins' Darin Mastroianni during an unsuccessful double play during the third inning of a baseball game on Tuesday, Sept. 17, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Recent Work

Philadelphia Phillies catcher Carlos Ruiz loses a foul ball hit by the Chicago Cubs' Donnie Murphy to the crowd during the sixth inning of a baseball game on Saturday, Aug. 31, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Chicago Cubs' Darwin Barney safely steals second base under Philadelphia Phillies second baseman Chase Utley during the sixth inning of a baseball game on Saturday, Aug. 31, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Philadelphia Phillies' Jimmy Rollins reacts to striking out against the Chicago Cubs during the first inning of a baseball game on Saturday, Aug. 31, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Chicago Cubs' Cole Gillespie hits a single against the Philadelphia Phillies during the second inning of a baseball game on Saturday, Aug. 31, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Chicago Cubs starting pitcher Jake Arrieta pitches against the Philadelphia Phillies during the first inning of a baseball game on Sunday, Sept. 1, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Chicago Cubs' Ryan Sweeney hits a single against the Philadelphia Phillies during the first inning of a baseball game on Sunday, Sept. 1, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Philadelphia Phillies right fielder Darin Ruf misses the catch on a double hit by the Chicago Cubs' Anthony Rizzo during the third inning of a baseball game on Sunday, Sept. 1, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Chicago Cubs' Starlin Castro is hit by a pitch during the fourth inning of a baseball game against the Philadelphia Phillies on Sunday, Sept. 1, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Chicago Cubs' Welington Castillo safely reaches home as Philadelphia Phillies catcher Erik Kratz loses the ball during the fourth inning of a baseball game on Sunday, Sept. 1, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Philadelphia Phillies catcher Erik Kratz heads back to the plate after the Chicago Cubs' Welington Castillo scored during the fourth inning of a baseball game on Sunday, Sept. 1, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Philadelphia Phillies relief pitcher Jacob Diekman pitches against the Chicago Cubs during the seventh inning of a baseball game on Sunday, Sept. 1, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Chicago Cubs' Junior Lake rounds the bases after hitting a grand slam against the Milwaukee Brewers during the first inning of a baseball game on Friday, Sept. 6, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Milwaukee Brewers' Norichika Aoki hits a sacrifice fly against the Chicago Cubs allowing Jeff Bianchi to score during the second inning of a baseball game on Friday, Sept. 6, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Chicago Cubs relief pitcher Pedro Strop meets with catcher Welington Castillo after giving up three runs during the eighth inning of a baseball game on Friday, Sept. 6, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Milwaukee Brewers first baseman Sean Halton leaps for a catch as the Chicago Cubs' Welington Castillo safely reaches first on a single during the eighth inning of a baseball game on Friday, Sept. 6, 2013, in Chicago. (AP Photo/Andrew A. Nelles)

Illinois Fighting Illini fans during the first half of the NCAA football game against the Cincinnati Bearcats on Saturday, Sept. 7, 2013, in Champaign, Ill. (AP Photo/Andrew A. Nelles)

Illinois Fighting Illini quarterback Nathan Scheelhaase (2) hands off to running back Josh Ferguson (6) during the first half of their NCAA football game on Saturday, Sept. 7, 2013, in Champaign, Ill. (AP Photo/Andrew A. Nelles)

Illinois Fighting Illini running back Josh Ferguson (6) receives a pass before running in a touch down during the first half of their NCAA football game on Saturday, Sept. 7, 2013, in Champaign, Ill. (AP Photo/Andrew A. Nelles)

llinois Fighting Illini wide receiver Ryan Lankford (12) runs in a touchdown during the first half of their NCAA football game on Saturday, Sept. 7, 2013, in Champaign, Ill. (AP Photo/Andrew A. Nelles)

llinois Fighting Illini wide receiver Ryan Lankford (12) celebrates after scoring a touchdown during the first half of their NCAA football game on Saturday, Sept. 7, 2013, in Champaign, Ill. (AP Photo/Andrew A. Nelles)

Cincinnati Bearcats running back Ralph Abernathy (1) is tackled by Illinois Fighting Illini linebacker Jonathan Brown (45) during the first half of their NCAA football game on Saturday, Sept. 7, 2013, in Champaign, Ill. (AP Photo/Andrew A. Nelles)

Illinois wide receiver Steve Hull (9) scores a touchdown in front of Cincinnati safety Arryn Chenault (25) during the second half of their NCAA college football game on Saturday, Sept. 7, 2013, in Champaign, Ill. (AP Photo/Andrew A. Nelles)

Cincinnati quarterback Munchie Legaux (4) hands off to running back Ralph Abernathy (1) during the second half of their NCAA college football game against Illinois on Saturday, Sept. 7, 2013, in Champaign, Ill. (AP Photo/Andrew A. Nelles)

Cincinnati quarterback Munchie Legaux is tended to after being injured during the second half of an NCAA college football game against Illinois on Saturday, Sept. 7, 2013, in Champaign, Ill. (AP Photo/Andrew A. Nelles)

Illinois' players celebrate after their 45 to 17 victory over Cincinnati in a NCAA college football game on Saturday, Sept. 7, 2013, in Champaign, Ill. (AP Photo/Andrew A. Nelles)

Writer Mike Comerford works the carousel ride at the Puerto Rico Fest in Chicago on Sunday, June 16, 2013. Mike Comerford, a former newspaper journalist, has been working as a carnival ride operator and writing about the experience.  (Andrew A. Nelles / For The Chicago Tribune)