Background:  Sacro-­‐iliac  (SI)  joint  fusion  is  a  rapidly  growing  market  in  spinal  orthopedics.  The  procedure  is  becoming  more  commonplace  as  clinicians  realize  that   they   have   been   misdiagnosing   SI   joint   pain   as  emanaAng  from  the  lumbar  spine.    

Design  Problem:  There  are   two  types  of   implants  that   surgeons   use   for   SI   Joint   Fusion:   Screws   and  Fusion  Rods.  Screws  and  used  to  fixate  and  compress  the  joint,  whereas  fusion  rods  are  used  to  fuse  bone  to   the   implant   to  help   increase  fixaAon  of   the   joint.  Surgeons   requested   Screws   that   allow   the   user   to  pack  bone  graJ  into  the  implant  to  allow  for  fixaAon  and  bone   fusion,   and   Fusion  Rod   implants   that   had  more  surface  area  for  greater  bony  fixaAon.  

Screw  Design  Highlights:  

The   SIJFuse   Screws   were   designed   with   a   large  enough   cannulaAon   to   allow   the   surgeon   to   pack  bone   graJ   through   the   implant.   Fusion   holes   allow  bone   graJ   to   contact   surrounding   bone   for   fusion.  Fusion  holes  are  paKerned  along  a  helix   for   greater  strength  in  bending.  

 

SIJFuse®  Implant  Designs    

Fusion  Rod  Design  Highlights:  

The  fusion  rods  were  designed  uAlizing  a  6-­‐point  star  shape  so  that  the  implant  has  50%  more  surface  area  than  compeAtor  implants  of  the  same  “diameter”  and  length.   Two   versions   of   the   implants   are   available:   a  fusion   rod   with   a   solid   core   and   porous   surface   to  allow  for  fusion  onto  the  surface,  and  an  implant  with  a  laScework  core  to  allow  for  bony  ingrowth  into  and  through   the   implant,   made   uAlizing   DMLS   addiAve  manufacturing.  

Implant  Expulsion  Resistance  

Design  Problem:  Surgeons  reported    few  instances  of   1st   generaAon   T-­‐LIFT   implants   backing   out   of   the  vertebral   disc   space   aJer   implantaAon.   Root   cause  analysis  lead  to  the  conclusion  that  the  tooth  design  of  the  implant  did  not  allow  for  proper  fixaAon  in  the  disc  space.  

The   direcAon   of   the   teeth   allowed   the   implant   to  resist  moAon  in  the  anterior-­‐posterior  direcAon,  but  the  implant  did  not  adequately  resist  pushout  forces  along  the  posterior-­‐oblique  window  through  which  it  was  inserted.  

Dorado  T-­‐LIFT®  Implant  Redesign    

The   first   iteraAon   of   the   new   T-­‐LIFT   featured   teeth  designed   to   resist   movement   in   the   direcAon   of  inserAon.   The   teeth  were  designed   conservaAvely   so  that   they   did   not   break   in   faAgue   tesAng   per   ASTM  F2077.   However,   the   pushout   resistance   of   the  implant   was   only   marginally   improved.   A   more  aggressive   design   was   needed   to   beKer   resist   the  pushout,   while   balancing   performance   in   faAgue  tesAng.  

1st  Itera4on  

InserAon  DirecAo

n  

Implant  Teeth  

2nd  Itera4on  

Dorado  T-­‐LIFT®  Implant  Redesign    

The   2nd   iteraAon   of   the   T-­‐LIFT   design   featured   teeth  that  are  far  more  aggressive  than  the  1st  iteraAon.    

The  teeth  were  designed  to  allow  for  ease  of  inserAon  while  sAll  resisAng  pushout.  Movement  of  the  implant  toward  the  paAent’s  anterior  was  not  deemed  a  risk,  as  surgeons  leave  the  anterior  annulus  fibrosis  in-­‐tact.      

Many   iteraAons  of   this  design  were  created,  working  to   achieve   balance   between   pushout   strength   and  compressive   faAgue   life.  Tooth  geometry  such  as   the  tooth   point   (flat   tooth   vs.   sharp   tooth),   tooth   angle,  and   tooth   spacing   were   the   parameters  modified   to  opAmize  the  implant  design.    

A   combinaAon   of   FEA   simulaAng   ASTM   tesAng   and  prototype   bench   tesAng   were   used   to   evaluate   the  strength  of  the  design.    

The   pictured   design   was   the   implant   that   best  balanced   pushout   strength   and   faAgue   life.   This  design  was  ulAmately  submiKed  to  the  FDA  for  510(k)  clearance,  and  has  been  used  in  clinical  pracAce  since  January  2012.  

Compression  Test  FEA  

Design   Task:   Design   a   product   that   demonstrates  the   ability   of   the   Connex   line   of   3D   printers   to   print  mulAple  materials  simultaneously.    

For  this  task,  I  chose  to  design  a  flashlight,  as  consumer  flashlights  contain  mulAple  materials,  ranging  from  hard  plasAcs  to  silicone  overmolds  of  differing  durometers.    

Design  Concepts:    The  main  area  of  focus  for  this  project  was   the   feel   of   the   flashlight   in-­‐hand.  My   research   of   available    products  revealed  many  soJ-­‐touch,  paKerned  silicone  overmolds  which  give  the  flashlight  a  secure  and  comfortable  grip.  

I  developed  several  grip  concepts,  but  ulAmately  chose  a  studded  grip  paKern  as  opposed  to  a  ribbed  or  diamond  knurl  paKern.  The  studs,  I  felt,  gave  the  grip  a  beKer  feel  in-­‐hand.    

           

Preliminary  Design  

Concept  Drawings  

Challenges:  The  problem  with  the  first  design  iteraAon  was   the   grip   feel.   The   grip   did   not   have   the   desired  “squishiness”,  due  to  the  thickness  of  the  overmold  and  the  differing  material  properAes  between  silicone  and  the  Objet  rubber  material.  The  funcAon  of  the  grip  design  also  proved  troublesome,   as   the   studs   on   the   overmold   were   easily  scraped  off  during  use  and  transport.  Since  the  product  was  intended   to   be   displayed   at   a   tradeshow   and   handled   by  many  people,  this  design  was  inadequate.  

Final  Design  For   the   final   iteraAon,   I   addressed   the   deficiencies   with   the   grip  design.  By  making  the  grip  studs  larger,  the  grip  had  a  springier  feel  and   felt  more   akin   to   silicone.   In   addiAon,   the   larger   studs   beKer  resisted   stripping   as   compared   to   the  first   iteraAon.   This   provided  beKer  longevity  for  the  show  piece.    

The   new   design   was   tested   for   durability   by   other   employees   of  Objet.   Employees   carried   the  flashlights   to   and   from  work   in   their  briefcases   and  work   bags,   and   handled   the   flashlights   periodically  throughout  the  work  day.  With  this  new  design,  the  flashlight  grips  lasted   for   several   weeks   on   average,   which   is   a   long   life-­‐cycle  considering   the   deficient   material   properAes   of   Objet   resin.   The  markeAng   team   was   pleased   with   the   product   and   sent   fully  funcAonal  flashlights  out  to  the  sales  team  for  use  in  meeAngs.    

Personal  Projects  

Background:   Sedentary   lifestyles   lead   to   a   host   of   health  problems,   including   cardiovascular   disease   and   obesity.   These  problems  are  exacerbated  by  the  fact  that  our  society  spends  a  majority  of   their  day  siSng  while  at  work.  Sit-­‐stand  desks  have  been   gaining   popularity   as   they   allow   employees   to   stand   at  their  desk  and  sit  when  a  rest  is  needed.  

While   these   desks   offer   great   health   benefits,   there   are  many  problems   with   current   desk   designs.   Inexpensive   desks   are  staAcally   in   the   standing   posiAon,   necessitaAng   use   of   an  uncomfortable  high  chair  to  sit  at  the  desk.  Desks  that  allow  the  user   to  move   between   a   siSng   and   standing   posiAon   are   very  expensive,  upwards  of  $1500  per  desk.  In  addiAon,  these  require  the   user   to  manually  move   the   desk   from   one   posiAon   to   the  other,  which  is  cumbersome  and  annoying  for  the  user.    

Design:  The  desk  I  designed  uses  linear  actuators  to  move  the  desk   surface   from  a   siSng  posiAon   to   a   standing  posiAon.   The  actuators   are   controlled   by   a   program   on   the   user’s   computer  that  moves  the  desktop  surface  from  a   low  siSng  posiAon  to  a    desired   standing   posiAon   (up   to   12   inches   of  movement).   The  frame   of   the   desk   is   created   from   stock   80/20   Aluminum  extrusion,   anodized   black.   The   desktop   is   a   stock   table   surface  from  IKEA.  

This   design   addressed   all   of   the   shortcomings   of   commercially  available   desks:   allow   the   user   to   quickly   and   easily   go   from   a  siSng   posiAon   to   a   standing   posiAon,   and   have   a   reasonable  price  point  of  $500.    

Automated  Sit-­‐Stand  Desk   Desk  Posi4ons  

“The  High  Voltage  Fish”  Custom  Bass  Guitar  

           

The  High  Voltage  Fish   is  a  collaboraAve  effort  between  myself  and  Dave  Cohen,  personal  friend  and  owner  of  Equilibrium  Guitars.    Equilibrium  Guitars  is  a  start-­‐up  company  that  hand-­‐builds  custom  guitars  for  musicians  who  seek  unique  designs  and  cuSng-­‐edge  sounds.  

The  High  Voltage  Fish  aims  to  shake  the  bones  of  its  listeners.  It  is  a  neck-­‐thru  style  bass,  which  increases  the  sustain  of  the  instrument.  The  neck  is  made  from  a  laminate  of  Bloodwood  and  Black  Walnut.    This  wood  combinaAon  captures  a  sharp  aKack  and  adds  a  full  midrange  frequency  spectrum  to  the  instrument  sound  for  that  “growliness”  of  70’s  rock  and  metal.  The  body  wings  are  made  from  Padauk,  which  adds  warmth  and  further  punch  to  the  sound.    

For   the  body  and  headstock  design,   I  wanted  a  modern  streamlined   look   that  also  captured  the  aggressive  nature  of   the  guitar  sound  and  was  consistent  with  the  design  vision  Dave  has  for  his  instruments.  This  is  the  look  that  I  tried  to  capture  in  my  iniAal  concept  sketches,  which  I  am  sAll  in  the  process  of  finalizing  with  Dave.      

           

Concepts  &  Inspira4on  Gluing  the  Neck  Blank   Finished  Blank  

8-­‐String  Guitar  Bridge  

           

The  bridge  of  a  guitar  is  an  integral  piece  of  the  instrument.  It  anchors  the  strings  to  the  body  of  the  guitar  and  transmits  the  vibraAons   of   the   strings   to   the   wooden   body   of   the   instrument.   The   8-­‐String   fanned   fret   guitars   that   Dave   Cohen   of  Equilibrium  Guitars  creates  are  problemaAc  to  manufacture  as  no  bridge  parts  exist   for   these  exoAc   instruments.  Fanned  fret   guitars   require   an   angled   bridge   to   account   for   the   highly   varied   string   length   on   the   guitars   and   ensure   proper  intonaAon  of  the  instrument.  

I  met  with  Dave  to  create  his  specificaAons  for  the  bridge  components,  which  I  turned  into  CAD  models  and  drawings.  He  decided   that   he   wanted   the   bridge   to   be   made   from   brass,   which   was   ideal   for   sustaining   string   vibraAon   (and   for  machining!).  Before  creaAng  the  bridge  plates,   I  created  the  plan  to  fabricate  the  parts:  cut  the  stock  material  on  a  band  saw,  mill  the  holes  and  slots  by  placing  the  stock  in  a  vise  with  parallels,  and  then  put  the  part  in  a  fixture  to  mill  the  final  profile.  The  holes  of  the  parts  were  then  hand-­‐tapped  to  allow  the  bridge  saddles  to  be  aKached.  AJer  tapping,  the  plates  were  powder  coated  black  to  match  the  instrument  aestheAcs  and  laser-­‐marked  with  a  white  EQ  Guitars  logo.  

 

Plate  AMer  1st  Milling  Opera4on   Final  Profiling   Finished  Plate  

Spec  Sketches