Ƙarfin da ke aiki a kan layi a kan fuskar ruwa

Ana auna shi a cikin newton a kan mita (N/m) ko dyne a kan santimita (dyn/cm). Idan ka yi tunanin wani firam mai gefen da ke motsi wanda ke hulɗa da fim ɗin ruwa, tashin hankalin sama shine ƙarfin da ke jan wannan gefen an raba shi da tsayinsa. Wannan shine ma'anar inji.

Tsari: γ = F/L inda F = ƙarfi, L = tsayin gefe

Misali: Ruwa @ 20°C = 72.8 mN/m yana nufin ƙarfin 0.0728 N a kan kowane mita na gefe

Makamashin da ake buƙata don ƙirƙirar sabon fagen sama

Ana auna shi a cikin joule a kan murabba'in mita (J/m²) ko erg a kan murabba'in santimita (erg/cm²). Ƙirƙirar sabon fagen sama yana buƙatar aiki akan ƙarfin tsakanin kwayoyin halitta. A lissafi yana daidai da tashin hankalin sama amma yana wakiltar hangen nesa na makamashi maimakon hangen nesa na ƙarfi.

Tsari: γ = E/A inda E = makamashi, A = ƙaruwar fagen sama

Misali: Ruwa @ 20°C = 72.8 mJ/m² = 72.8 mN/m (lamba ɗaya, fassara biyu)

Ƙarfin tsakanin kwayoyin halitta yana ƙayyade halayen sama

Haɗin kai: jan hankali tsakanin kwayoyin halitta iri ɗaya (ruwa-ruwa). Mannewa: jan hankali tsakanin kwayoyin halitta daban-daban (ruwa-abu mai ƙarfi). Babban haɗin kai → babban tashin hankalin sama → ɗigon ruwa yana dunƙulewa. Babban mannewa → ruwa yana yaɗuwa (jike). Daidaituwa yana ƙayyade kusurwar hulɗa da aikin gashi.

Kusurwar hulɗa θ: cos θ = (γ_SV - γ_SL) / γ_LV (tsarin Young)

Misali: Ruwa a kan gilashi yana da ƙaramin θ (mannewa > haɗin kai) → yana yaɗuwa. Mercury a kan gilashi yana da babban θ (haɗin kai >> mannewa) → yana dunƙulewa.

Gwaje-gwajen farko na yawan tashin hankalin sama

Masani a fannin ilimin lissafi dan kasar Jamus Segner ya yi nazarin allurai masu iyo kuma ya lura cewa saman ruwa na nuna hali kamar fatun roba masu shimfiɗa. Ya lissafa karfin amma bai da ka'idar kwayar halitta don bayyana abin da ke faruwa.

Tsarin Young don kusurwar hulɗa

Masani a fannoni da yawa dan kasar Biritaniya Young ya samo alakar da ke tsakanin tashin hankalin sama, kusurwar hulɗa, da jike: cos θ = (γ_SV - γ_SL)/γ_LV. Har yanzu ana amfani da wannan muhimmin tsarin a yau a kimiyyar kayan aiki da microfluidics.

Tsarin Young-Laplace don matsi

Laplace ya samo ΔP = γ(1/R₁ + 1/R₂), yana nuna cewa saman da ke lanƙwasa na da bambancin matsi. Yana bayyana dalilin da yasa ƙananan kumfa ke da matsi mafi girma a ciki fiye da manya—wanda ke da mahimmanci don fahimtar ilimin halittar huhu da kwanciyar hankalin emulsion.

Ka'idar kwayar halitta ta tashin hankalin sama

Masani a fannin ilimin lissafi dan kasar Holland van der Waals ya bayyana tashin hankalin sama ta amfani da karfin tsakanin kwayoyin halitta. Aikinsa kan jan hankalin kwayar halitta ya ba shi lambar yabo ta Nobel a 1910 kuma ya kafa harsashin fahimtar capillary, mannewa, da mahimmin matsayi.

Monolayers da ilimin sunadarai na sama

Langmuir ya yi nazarin fina-finan kwayar halitta a saman ruwa, inda ya kirkiri fannin ilimin sunadarai na sama. Aikinsa kan abubuwan da ke aiki a sama, adsorption, da tsarin kwayar halitta ya ba shi lambar yabo ta Nobel a 1932. Ana kiran fina-finan Langmuir-Blodgett da sunansa.

Tashin hankalin sama yana ƙayyade jike, yaɗuwa, da mannewa:

• Tsarin fenti: Daidaita γ zuwa 25-35 mN/m don mafi kyawun yaɗuwa a kan saman abu
• Buga na inkjet: Tawada dole ne ta kasance da γ < saman abu don jike (yawanci 25-40 mN/m)
• Maganin korona: Yana ƙara makamashin saman polymer daga 30 → 50+ mN/m don mannewa
• Suturar foda: Ƙananan tashin hankalin sama na taimakawa wajen daidaitawa da haɓaka sheki
• Suturar da ke hana rubutu a bango: Ƙananan γ (15-20 mN/m) na hana mannewar fenti
• Kula da inganci: Tensiometer na zoben du Noüy don daidaito tsakanin batches

Sabulai suna aiki ta hanyar rage tashin hankalin sama:

• Ruwa mai tsafta: γ = 72.8 mN/m (ba ya shiga cikin yadudduka da kyau)
• Ruwa + sabulu: γ = 25-30 mN/m (yana shiga, yana jike, yana cire mai)
• Matsayin Micelle Mai Muhimmanci (CMC): γ yana raguwa sosai har zuwa CMC, sannan ya tsaya
• Wakilan jike: Masu tsabtace masana'antu suna rage γ zuwa <30 mN/m
• Ruwan wanke-wanke: An tsara shi zuwa γ ≈ 27-30 mN/m don cire maiko
• Masu fesa magungunan kashe kwari: Ƙara abubuwan da ke aiki a sama don rage γ don mafi kyawun rufe ganye

Tashin hankalin tsakanin man fetur da ruwa yana shafar fitarwa:

• Tashin hankalin tsakanin man fetur da ruwa: Yawanci 20-50 mN/m
• Ingantaccen fitar da mai (EOR): Allurar abubuwan da ke aiki a sama don rage γ zuwa <0.01 mN/m
• Ƙananan γ → ɗigon mai ya zama emulsion → yana gudana ta cikin dutsen da ke da ramuka → ƙaruwar fitarwa
• Bayyana ɗanyen mai: Abun cikin aromatic yana shafar tashin hankalin sama
• Gudun bututu: Ƙananan γ yana rage kwanciyar hankalin emulsion, yana taimakawa wajen rabuwa
• Hanyar ɗigon da aka rataye tana auna γ a zafin jiki/matsin lamba na ajiyar

Tashin hankalin sama yana da mahimmanci ga tsarin rayuwa:

• Surfaktant na huhu: Yana rage γ na alveoli daga 70 zuwa 25 mN/m, yana hana rugujewa
• Jarirai da aka haifa da wuri: Ciwon wahalar numfashi saboda rashin isasshen surfaktant
• Bangon kwayar halitta: γ na lipid bilayer ≈ 0.1-2 mN/m (yana da ƙanƙanta sosai don sassauci)
• Plasma jini: γ ≈ 50-60 mN/m, yana ƙaruwa a cikin cututtuka (ciwon sukari, atherosclerosis)
• Fim ɗin hawaye: Tsari mai yawa da ke da layin lipid wanda ke rage ƙafewa
• Numfashin kwari: Tsarin trachea ya dogara da tashin hankalin sama don hana shigar ruwa

Masu tafiya a kan ruwa (Gerridae) suna amfani da babban tashin hankalin saman ruwa (72.8 mN/m) don tallafawa nauyin jikinsu sau 15. Ƙafafunsu an rufe su da gashin gashi mai kakin zuma wanda ke da matukar ƙin ruwa (kusurwar hulɗa > 150°). Kowane ƙafa yana haifar da ɗan ƙaramin rami a saman ruwa, kuma tashin hankalin sama yana ba da ƙarfin sama. Idan ka ƙara sabulu (yana rage γ zuwa 30 mN/m), nan da nan suna nutsewa!

Tashin hankalin sama yana aiki don rage fagen sama don wani adadi. Ƙwallo tana da mafi ƙarancin fagen sama don kowane adadi (rashin daidaiton isoperimetric). Kumfar sabulu tana nuna wannan da kyau: iskar da ke ciki tana turawa waje, tashin hankalin sama yana jan ciki, kuma daidaito yana haifar da ƙwallo cikakke. Kumfa da ba su da siffar ƙwallo (kamar masu siffar cube a cikin firam ɗin waya) suna da makamashi mafi girma kuma ba su da kwanciyar hankali.

Huhuwan jarirai suna ɗauke da surfaktant na huhu (phospholipids + sunadarai) wanda ke rage tashin hankalin saman alveoli daga 70 zuwa 25 mN/m. Idan babu shi, alveoli suna rugujewa yayin fitar da numfashi (atelectasis). Jarirai da aka haifa da wuri ba su da isasshen surfaktant, wanda ke haifar da Ciwon Wahalar Numfashi (RDS). Kafin maganin surfaktant na roba (shekarun 1990), RDS shine babban dalilin mutuwar jarirai. Yanzu, yawan tsira ya wuce 95%.

Zuba giya a cikin gilashi kuma kalla: ɗigon ruwa ya bayyana a gefuna, ya hau sama, kuma ya sake faɗowa—'hawayen giya'. Wannan shine tasirin Marangoni: barasa tana ƙafewa da sauri fiye da ruwa, tana haifar da bambancin tashin hankalin sama (γ yana canzawa a wurare daban-daban). Ruwa yana gudana daga wurare masu ƙarancin γ zuwa wurare masu babban γ, yana jan giya sama. Lokacin da ɗigon ruwa ya yi nauyi sosai, nauyi ya yi nasara kuma suna faɗowa. Gudun Marangoni yana da mahimmanci a wajen walda, sutura, da girma na crystal.

Kwayoyin halittar sabulu suna da siffofi biyu: wutsiya mai ƙin ruwa + kai mai son ruwa. A cikin magani, wutsiyoyi suna fitowa daga saman ruwa, suna rushe haɗin hydrogen kuma suna rage γ daga 72 zuwa 25-30 mN/m. A Matsayin Micelle Mai Muhimmanci (CMC), kwayoyin halitta suna haifar da micelles masu siffar ƙwallo da wutsiyoyi a ciki (suna kama mai) da kawuna a waje. Wannan shine dalilin da yasa sabulu ke cire maiko: ana narkar da mai a cikin micelles kuma ana wanke shi.

Jefa kristal na camphor a kan ruwa kuma zai yi gudu a kan sama kamar ƙaramin jirgin ruwa. Camphor yana narkewa ba daidai ba, yana haifar da bambancin tashin hankalin sama (mafi girman γ a baya, ƙarami a gaba). Saman yana jan kristal zuwa wurare masu babban γ—injin tashin hankalin sama! Masani a fannin ilimin lissafi C.V. Boys ya nuna wannan a 1890. Masana ilmin sunadarai na zamani suna amfani da irin wannan motsi na Marangoni don micro-robots da motocin isar da magani.

Wannan muhimmin alaƙar zafin jiki ce, ba daidaituwa ba. A ma'auni: [N/m] = (kg·m/s²)/m = kg/s² da [J/m²] = (kg·m²/s²)/m² = kg/s². Suna da ma'auni iri ɗaya na asali! A zahiri: ƙirƙirar 1 m² na sabon sama yana buƙatar aiki = ƙarfi × nisa = (γ N/m) × (1 m) × (1 m) = γ J. Don haka γ da aka auna a matsayin ƙarfi/tsayi daidai yake da γ da aka auna a matsayin makamashi/fage. Ruwa @ 20°C: 72.8 mN/m = 72.8 mJ/m² (lamba ɗaya, fassara biyu).

Haɗin kai: jan hankali tsakanin kwayoyin halitta iri ɗaya (ruwa-ruwa). Mannewa: jan hankali tsakanin kwayoyin halitta daban-daban (ruwa-gilashi). Babban haɗin kai → babban tashin hankalin sama → ɗigon ruwa yana dunƙulewa (mercury a kan gilashi). Babban mannewa dangane da haɗin kai → ruwa yana yaɗuwa (ruwa a kan gilashi mai tsafta). Daidaituwa yana ƙayyade kusurwar hulɗa θ ta hanyar tsarin Young: cos θ = (γ_SV - γ_SL)/γ_LV. Jike yana faruwa lokacin da θ < 90°; dunƙulewa lokacin da θ > 90°. Fuskokin da ke da matukar ƙin ruwa (ganyen lotus) suna da θ > 150°.

Kwayoyin halittar sabulu suna da siffofi biyu: wutsiya mai ƙin ruwa + kai mai son ruwa. A kan iyakar ruwa da iska, wutsiyoyi suna fuskantar waje (suna guje wa ruwa), kuma kawuna suna fuskantar ciki (ruwa na jan su). Wannan yana rushe haɗin hydrogen tsakanin kwayoyin halittar ruwa a kan sama, yana rage tashin hankalin sama daga 72.8 zuwa 25-30 mN/m. Ƙananan γ yana ba wa ruwa damar jike yadudduka kuma ya shiga cikin maiko. A Matsayin Micelle Mai Muhimmanci (CMC, yawanci 0.1-1%), kwayoyin halitta suna haifar da micelles waɗanda ke narkar da mai.

Babban zafin jiki yana ba wa kwayoyin halitta ƙarin makamashin motsi, yana raunana jan hankalin tsakanin kwayoyin halitta (haɗin hydrogen, ƙarfin van der Waals). Kwayoyin halittar sama suna da ƙarancin jan hankali zuwa ciki → ƙarancin tashin hankalin sama. Don ruwa: γ yana raguwa da ~0.15 mN/m a kowace °C. A zafin jiki mai mahimmanci (374°C don ruwa, 647 K), bambancin ruwa da iska ya ɓace kuma γ → 0. Dokar Eötvös ta ƙididdige wannan: γ·V^(2/3) = k(T_c - T) inda V = girman mola, T_c = zafin jiki mai mahimmanci.

Hanyoyi huɗu na asali: (1) Zoben du Noüy: Ana jan zoben platinum daga sama, ana auna ƙarfin (mafi yawa, ±0.1 mN/m). (2) Farantin Wilhelmy: Ana rataye faranti mai laushi wanda ke taɓa sama, ana auna ƙarfin a kai a kai (mafi inganci, ±0.01 mN/m). (3) Ɗigon da aka rataye: Ana nazarin siffar ɗigon ta hanyar gani ta amfani da tsarin Young-Laplace (yana aiki a babban T/P). (4) Hawan gashi: Ruwa yana hawa a cikin bututu mai siriri, ana auna tsayin: γ = ρghr/(2cosθ) inda ρ = yawa, h = tsayi, r = radius, θ = kusurwar hulɗa.

ΔP = γ(1/R₁ + 1/R₂) yana bayyana bambancin matsi a kan saman da ke lanƙwasa. R₁ da R₂ sune manyan radius na lanƙwasa. Don ƙwallo (kumfa, ɗigon ruwa): ΔP = 2γ/R. Ƙananan kumfa suna da matsi mafi girma a ciki fiye da manya. Misali: ɗigon ruwa 1 mm yana da ΔP = 2×0.0728/0.0005 = 291 Pa (0.003 atm). Wannan yana bayyana dalilin da yasa ƙananan kumfa a cikin kumfa suke raguwa (gas yana yaɗuwa daga ƙanana zuwa manya) kuma dalilin da yasa alveoli na huhu ke buƙatar surfaktant (yana rage γ don kada su ruguje).

Mercury: Ƙarfin haɗin kai (haɗin ƙarfe, γ = 486 mN/m) >> ƙarancin mannewa ga gilashi → kusurwar hulɗa θ ≈ 140° → yana dunƙulewa. Ruwa: Matsakaicin haɗin kai (haɗin hydrogen, γ = 72.8 mN/m) < ƙarfin mannewa ga gilashi (haɗin hydrogen da rukunin -OH na sama) → θ ≈ 0-20° → yana yaɗuwa. Tsarin Young: cos θ = (γ_abu mai ƙarfi-tururi - γ_abu mai ƙarfi-ruwa)/γ_ruwa-tururi. Lokacin da mannewa > haɗin kai, cos θ > 0, don haka θ < 90° (jike).

A'a. Tashin hankalin sama koyaushe yana da kyau—yana wakiltar farashin makamashi don ƙirƙirar sabon fagen sama. Mara kyau γ zai nuna cewa fuskoki za su faɗaɗa da kansu, suna karya dokokin zafin jiki (entropy yana ƙaruwa, amma babban lokaci ya fi kwanciyar hankali). Koyaya, tashin hankalin tsakanin ruwaye biyu zai iya zama ƙanƙanta sosai (kusa da sifili): a cikin ingantaccen fitar da mai, abubuwan da ke aiki a sama suna rage γ na mai da ruwa zuwa <0.01 mN/m, suna haifar da emulsion da kansa. A mahimmin matsayi, γ = 0 daidai (bambancin ruwa da iska ya ɓace).