Design of Diaphragm Micro-Devices. (Due date: Nov 2, 2017)

Transcription

1 Design f Diphrgm Micr-Devices (Due de: Nv, 017) 1. Bckgrund A number f micr-devices depend upn diphrgm fr heir perin. Such devices re vlve, pump, nd pressure sensr. The generlized mdel f hese devices is shwn in Fig. 1 Fig. 1 where rdius f diphrgm hickness f diphrgm y displcemen f cener f diphrgm P pressure due fluid in flw re d pr dimeer r rdius f hlf-rund duc nminl spcing f cpcir ples r rdius f cpcir ples V elecrsic vlge P elecrsic pressure Displcemen nd Sress (ny unis): Fr micr-sized devices, he diphrgm usully is very hin cmpred he displcemen. Cnsequenly, he membrne sress is pprecible. Fr his resn, he frmule fr displcemen nd fr sress include bh flexurl nd membrne sresses. The displcemen is given by P E Y +.6 Y ν 1 ν (1)

2 where ν Pissn's ri E Yung's mdulus And sress is given by S Y Y E 1 ν () The sress S develped in he diphrgm mus be less hn he yield sress f he merils. Diphrgm Aspec Ris In rder fr he diphrgm deflec prperly, bh he hickness nd he displcemen shuld be very much smll hn he diphrgm rdius 100 (3) 100 Y (4) Flw Ares Fr design f flw res, hrugh he vlve pr, d A p p (5) hrugh he hlf rund duc 1 Ad π r (6) hrugh he pened vlve (ne h his re is pprximely cylinder bnded by diphrgm nd he subsre) A v πdy (7) In rder h ll hree res be equl (fr efficien fluid flw hrugh he enire device), eque Eqs (5)-(7) nd simplify d 4Y (8) nd d r (9) Sensrs nd Acurs The diphrgm device cn be used s eiher pressure sensr he mesure he fluidic pressure r n cur cnrl he vlve (pen r clse). Oupu sensrs Three upu sensrs my be used in he diphrgm device: piezresisive elemen (such s srin guge), piezelecric elemen, nd cpciive device. A srin guge is resisnce device whse resisnce chnges wih srin. A piezelecric elemen develps vlge due srin. A prllel ple cpcir is ne whse cpcince chnges wih spcing f he ples. Fr srin guge nd piezelecric sensrs, he upu is n liner nd usully is clibred empiriclly. The generl relinships my be given respecively by R R( x) (10) V V ( x) (11) Fr cpcir, he cpcince fr prllel ple is

3 C εa (1) Where A πr (13) Fr he upu sensrs, In rder prduce he lrges upu pssible, he designer is emped mke he cpcir ples s lrge s pssible. Hwever, here is rde-ff: Only he chnge in cpcince prduces n upu. This suggess he use f nly he cener f he diphrgm. As fir cmprmise, le 4 (fr sensr) r (14) In rder minimize he influence f displcemen n he cpciive effecs, le 10 Y (15) Sic Acur Fr udi frequencies ( Hz) piezelecric elemen is effecive. Fr smll size nd lw vlge, i prduces cmprbly lrge frce. Fr cpciive cur, i is recmmended h he enire surfce f he diphrgm be used. This is n verindulgence, bu mens re he diphrgm like membrne. Since he diphrgm will ms likely be very hin, unifrm pressure ver is enire surfce is preferble ld cncenred in smll re. In his cse, le r (fr cur) (16) The enire surfce ws used becuse f he membrne nure f he diphrgm. Hwever, cre mus be exercised in selecing he nminl gp. T ge he ms cin frm he elecrsic cur, he ple dimeer r shuld be bu 0 imes he gp. This gp is ls gd fr he prper cpcir perin. Then le r 0 (17) 0 The elecrsic frce fr cpciive cur is given s V εa F (18) Slve fr he vlge V, F F V (19) επr r επ T vid crn, rcing nd her elecricl prblems, i is necessry check h he vlge grdien γ des n exceed he llwed vlue. The grdien is V γ (0) The llwble grdien γ llw is funcin f medium (dielecric) beween he ples nd n he ples hemselves. Fr exmple, eher hs dielecric permiiviy ε40x10-1 F/m, nd n llwble vlge grdien γ 5x10 6 V/m. Since he elecrsic frce is unifrmly disribued ver he enire surfce f he diphrgm, i my be cnsidered n elecrsic pressure P, where

4 V ε ε V F P (1) A Apply he llwble vlge F ε P ( ) γ llw () A Vibrr cur Since he displcemen f hin diphrgm is nnliner, here will be sme difficuly in cmpuing he nurl frequency. Hence, nly rugh pprximin will be ffered. (The cul vlue shuld be deermined empiriclly.) ω n ( rd / s) (3) The dvnge f using vibrr cur is h, resnnce, he dynmic frce F d required prduce displcemen Y is less hn he sic frce F s, Fs F d (4) R Where R r is given by r 1 1 ς 1 ς R r (5) Where ζ is he dmping ri. This is he l f dmping surces, such s srucurl dmping, fluid resisnce, elecrsic dmping, nd s n. The dmped resnnce frequency is given s ω r ω n 1 ς (6). Design f diphrgm pressure sensr: Using diphrgm, pressure cn be mesured. The diphrgm is defleced by he pressure, nd his pressure, in urn, is mesured by srin guge r by cpcir. The fbricin prcess mkes use f scked chips, where n precisin lignmen is required. Ech chip is ced wih film f glss s h under high emperure nd pressure he chips becme self-bnding (Fig). Fig.

5 Design silicn diphrgm pressure sensr [see Fig.()] fr pressure equl 367 N/m. The Yung s mdulus nd yield srengh fr silicn re 1.9x10 11 N/m, nd 4.x10 8 N/m, respecively. The mximum dimeer f he diphrgm yu my chse is 1000µm. Als deermine he sensiiviy f yur sensr, C/C. 3. Design f diphrgm cnrl vlve The vlve uses diphrgm prvide min. Frm srucure pin f view, he diphrgm is reed s disk wih clmped edge (Fig.3) Fig.3 The vlve shwn in Fig. 3() is nrmlly pen. Air pressure cing gins he diphrgm clses he vlve. Ne h he ir supply des n mix wih he fluid h vlve is hndling. The vlve shwn in Fig. 3(b) is nrmlly clse. The vlve is pened by elecrsic frces n he elecrde ple ched he diphrgm. The diphrgm is bnded he bse hus des n llw he w fluids mix. Since he elecrnics culd be inegred in he p ple, i is unnecessry ech hle in he p wfer. Design silicn micr-cnrl vlve [see Fig.3(b)]. Assume h he chmber is filled wih eher. Als ssume h fluid pressure P f 133 N/m. The mximum dimeer f he diphrgm yu my chse is 1000µm.