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Mikro- und Nanosysteme Prof. Dr. Christofer Hierold

http://www.micro.mavt.ethz.ch

Masters  Thesis  /  Semester  project  

Biomimetic  microhairs  for  zero-­‐power  MEMS  actuators    

Motivation  Micro-­‐Electro-­‐Mechanical-­‐Systems   (MEMS)  use   actuators   for   a   multitude   of   tasks   like  moving,   gripping,   switching,   lifting  and   tilting  of   objects.   Applications   can   be   found   in  bioMEMS,   micro-­‐optics,   microelectronics,  microfluidics  and  many  other  fields.    Actuators  need  some  sort  of  energy   to  oper-­‐ate   and   typically   this   energy   is   supplied   in  form  of  electric  power.  An  electric  current  can  for  example  be  used  to  deform  a  piezoelectric  material   or   to   deform   a   bimetallic   structure  by  resistive  heating.    In   emerging   energy   harvesting   applications  for   the   Internet-­‐of-­‐Things   (IOT)   energy   is   a  very   limited   resource.     As   a   result,   systems  need   to   be   as   efficient   as   possible   to   work  with  the  very  small  available  energy  budget.  In   this   project,   a   zero-­‐power   actuator   is   de-­‐veloped  that  mimics  the  behavior  of  mammal  hair  when  exposed  to  temperature  changes.      

   Figure 1: Bimetallic microhairs that rise and fall with ambient temperature changes      

Approach  Nature  uses  tiny  muscles  (arrector  pili)  at  the  base   of   each   hair   to   erect   it   when   the   envi-­‐ronmental  temperature  falls.  We  will  replicate  this   effect   by   using   artificial   bimorph   micro-­‐hairs   that   can   bend   up   or   downwards   with  changing  temperature.  Hairs  are  fabricated  in  the  cleanroom  from  two  connected  polymers  with   a   large   difference   in   CTE   (coefficient   of  thermal   expansion).  Mechanical   stress   in   the  material  will  cause  a  deformation  of  the  hairs  as   function   of   the   temperature   according   to  the  bimetallic  effect.  Depending  on  the  design  of  the  structures,  they  can  be  used  for  a  varie-­‐ty  of  actuator  applications.    Task  description  Design   of   MEMS   photolithography   masks,  cleanroom   fabrication   of  microhairs   in   BRNC  (IBM,  Rüschlikon)  and  FIRST  (CLA,  ETHZ).  Tes-­‐ting   and   evaluation   of   the   fabricated   actua-­‐tors  for  different  applications.    Learning  opportunities  You  will  learn  how:  1. To  design  photolithography  masks  2. Work  in  the  cleanroom  3. Operate  cleanroom  equipment  4. To   use   experimental   tools   and   charac-­‐

terization  techniques  5. Work  independently  and  systematically  6. Write  a  good  scientific  report.  

 Contact:  Moritz  Thielen  Micro  and  Nanosystems,  CLA  G11.2  Email:  thielen@ethz.ch  Phone:  +41  44  632  2522  

2 mm