魯雯玥 嚴(yán)語(yǔ)欣 陳幸 宋文芳
Research progress and trend of medical protective clothing to alleviate human thermal stress
摘要:目前醫(yī)用防護(hù)服裝存在熱濕舒適性差的問(wèn)題,容易造成人體熱應(yīng)激,引起人體皮膚損傷、虛脫、暈眩甚至中暑等癥狀。為了解如何緩解醫(yī)用防護(hù)服裝造成的人體熱應(yīng)激反應(yīng),提高人體舒適性,文章首先總結(jié)了醫(yī)用防護(hù)服裝的材料、款式及舒適性相關(guān)標(biāo)準(zhǔn)。接著闡述了目前緩解人體熱應(yīng)激的醫(yī)用防護(hù)服裝研究進(jìn)展,包括作業(yè)場(chǎng)所降溫方式和異質(zhì)結(jié)構(gòu)面料、超吸水材料、輻射降溫面料、相變冷卻降溫服裝等研究成果。隨后介紹了高導(dǎo)熱材料、熱電冷卻材料和液態(tài)冷卻三類緩解人體熱應(yīng)激的新材料與技術(shù),并提出了其在醫(yī)用防護(hù)服裝上的應(yīng)用思路。最后分析并展望了緩解人體熱應(yīng)激的醫(yī)用防護(hù)服裝研究趨勢(shì),即未來(lái)研究需要從提高主動(dòng)冷卻設(shè)備的工效性能、擴(kuò)展調(diào)溫新材料與技術(shù)在醫(yī)用防護(hù)服裝上的應(yīng)用及建立緩解人體熱應(yīng)激的醫(yī)用防護(hù)服裝設(shè)計(jì)方法和流程,并開(kāi)展相關(guān)測(cè)試與評(píng)價(jià)。
關(guān)鍵詞:醫(yī)用防護(hù)服裝;熱應(yīng)激;熱濕舒適性;調(diào)溫材料與技術(shù);工效性;服裝設(shè)計(jì)與評(píng)價(jià)
中圖分類號(hào):TS941.731??? 文獻(xiàn)標(biāo)志碼:A???文章編號(hào): 10017003(2023)090073
引用頁(yè)碼:091109? ? DOI: 10.3969/j.issn.1001-7003.2023.09.009(篇序)
醫(yī)用防護(hù)服裝可以阻隔攜帶病菌的血液、體液、分泌物及空氣中的微粒,保障醫(yī)務(wù)工作者的生命安全,在新型冠狀病毒防治工作中發(fā)揮了重要作用,但也存在著突出的熱濕舒適性差問(wèn)題:醫(yī)護(hù)人員長(zhǎng)時(shí)間作業(yè)時(shí)大多表現(xiàn)出熱相關(guān)疾病,如頭痛、虛脫、皮膚損傷、暈眩甚至中暑等癥狀[1-2]。特別是近年來(lái)極端高溫天氣頻發(fā),該問(wèn)題更為顯著[3-4]。
醫(yī)用防護(hù)服裝為保證對(duì)病原微生物良好的阻隔性,面料纖維結(jié)構(gòu)致密,孔徑小而少,并且纖維材料多為疏水性的聚丙烯、聚乙烯纖維。這種組合可以有效提升防護(hù)服的防護(hù)性,但同時(shí)也會(huì)造成其較差的透濕透氣性能[5]。如何降低相關(guān)人員熱應(yīng)激反應(yīng),提高人體舒適感、健康與安全是應(yīng)當(dāng)重點(diǎn)關(guān)注的問(wèn)題。本文綜述了緩解人體熱應(yīng)激的醫(yī)用防護(hù)服裝的設(shè)計(jì),總結(jié)分析了降溫材料和技術(shù)的應(yīng)用進(jìn)展情況,同時(shí)結(jié)合材料與技術(shù)發(fā)展現(xiàn)狀,分析了緩解人體熱應(yīng)激的醫(yī)用防護(hù)服裝研究趨勢(shì),以期為提高醫(yī)護(hù)人員的安全、舒適度和健康指數(shù)提供參考。
1 醫(yī)用防護(hù)服裝的材料、款式及舒適性
目前防護(hù)服材料主要包括SMS復(fù)合非織造材料、閃蒸法非織造材料和層壓復(fù)合材料[6-8]。SMS復(fù)合非織造材料采用熔噴非織造材料為芯層,紡黏非織造材料為表面層[6],用于制作一次性隔離服和手術(shù)衣[7]。閃蒸法高密度聚乙烯非織造材料,又稱特衛(wèi)強(qiáng)(Tyvek)材料,采用閃蒸法制備,具備優(yōu)良的微生物阻隔性、抗撕裂性和防水透氣性,但其不耐高溫,無(wú)法進(jìn)行高溫洗消,因此只適合用于制造醫(yī)用一次性防護(hù)服裝[9]。以往閃蒸法工藝由美國(guó)杜邦公司壟斷,現(xiàn)階段廈門(mén)當(dāng)盛新材料有限公司和天津工業(yè)大學(xué)團(tuán)隊(duì)成功對(duì)閃蒸技術(shù)和設(shè)備申請(qǐng)了專利,實(shí)現(xiàn)了閃蒸紡絲技術(shù)的國(guó)產(chǎn)化。層壓復(fù)合材料多采用聚乙烯(PE)微孔膜、聚四氟乙烯(PTFE)微孔膜、熱塑性聚氨酯彈性體橡膠(TPU)微孔膜等為防護(hù)阻隔層,通過(guò)離線復(fù)合的加工方式將阻隔膜材與其他織物復(fù)合來(lái)制備防護(hù)服材料[8]。用于制作醫(yī)用一次性防護(hù)服裝的層壓復(fù)合材料多以紡黏或水刺非織造材料為基布,以更便宜、性價(jià)比更高的PE微孔膜為阻隔層,采用一布一膜(SF)或二布一膜(SFS)兩種覆膜形式將兩者復(fù)合得到[7]。而重復(fù)性使用醫(yī)用防護(hù)服裝多以PTFE微孔膜為阻隔層,以滌綸織物為內(nèi)外層制成三層復(fù)合材料[10-11]。相比其他阻隔膜材,采用PTFE制備的層壓織物具備更佳的阻隔性和透濕性[8]。
在款式與色彩方面,隔離服和手術(shù)衣為倒背式,色彩多為藍(lán)色;接觸傳染病患用醫(yī)用防護(hù)服裝主要有連體連帽式和分體結(jié)構(gòu)式兩種,色彩以白色和淺藍(lán)為主。其中連體連帽式醫(yī)用防護(hù)服裝具備良好的結(jié)構(gòu)密閉性和材料防護(hù)阻隔性,廣泛用于傳染病的防治。連體連帽式醫(yī)用一次性防護(hù)服裝的結(jié)構(gòu)如圖1所示,其采用兩片帽或三片帽設(shè)計(jì),接縫處使用膠條密封,杜絕水、氣、病菌從接縫處滲漏[12],拉鏈門(mén)襟設(shè)計(jì)方便穿脫,帽檐、袖口、褲腳采用彈性收口加強(qiáng)密封性,腰部采用半圈或整圈松緊提高合身性[13]。另外,醫(yī)護(hù)人員實(shí)際工作中需佩戴口罩、護(hù)目鏡或防護(hù)面罩,以及乳膠手套和鞋套增強(qiáng)防護(hù)性。重復(fù)性使用醫(yī)用防護(hù)服裝結(jié)構(gòu)與醫(yī)用一次性防護(hù)服裝大體一致,但為保證重復(fù)洗滌后的密封性,會(huì)在接縫密封、拉鏈選擇和袖口褲腳設(shè)計(jì)等方面有所差異[14]。
在熱濕舒適性評(píng)價(jià)指標(biāo)及標(biāo)準(zhǔn)方面,國(guó)內(nèi)醫(yī)用防護(hù)服裝相關(guān)標(biāo)準(zhǔn)GB 19082—2009《醫(yī)用一次性防護(hù)服技術(shù)要求》和YY/T 1799—2020《可重復(fù)使用醫(yī)用防護(hù)服技術(shù)要求》,規(guī)定材料透濕量應(yīng)不小于2 500 g/(m2·d),美國(guó)標(biāo)準(zhǔn)NFPA 1999—2018《緊急醫(yī)療操作用防護(hù)服和套裝標(biāo)準(zhǔn)》則是要求總體熱損失須大于450 W/m[15]。然而在實(shí)際作業(yè)中,學(xué)者們通過(guò)問(wèn)卷調(diào)研及人體熱生理實(shí)驗(yàn)研究均發(fā)現(xiàn),醫(yī)護(hù)人員穿著醫(yī)用防護(hù)服裝會(huì)出現(xiàn)熱應(yīng)激反應(yīng)[16-17]??梢?jiàn),目前醫(yī)用防護(hù)服裝的標(biāo)準(zhǔn)并不能滿足醫(yī)護(hù)人員實(shí)際穿著舒適性要求,需要通過(guò)材料和技術(shù)的研究及應(yīng)用來(lái)緩解人體熱應(yīng)激,并通過(guò)人體穿著實(shí)驗(yàn)對(duì)防護(hù)服裝進(jìn)行測(cè)試與評(píng)價(jià),進(jìn)一步完善標(biāo)準(zhǔn)。
2 緩解人體熱應(yīng)激的醫(yī)用防護(hù)服裝研究現(xiàn)狀及進(jìn)展
在實(shí)際作業(yè)現(xiàn)場(chǎng),目前已有的緩解醫(yī)護(hù)人員熱應(yīng)激的方法主要包括風(fēng)扇降溫、使用冰馬甲和正壓防護(hù)服等。另外,學(xué)術(shù)界也對(duì)醫(yī)用防護(hù)服裝用降溫材料進(jìn)行了廣泛研究和探討,主要降溫材料有異質(zhì)結(jié)構(gòu)面料、超吸水材料、輻射降溫面料、相變材料等。本文主要闡述相關(guān)材料與技術(shù)在醫(yī)用防護(hù)服裝上的應(yīng)用現(xiàn)狀、進(jìn)展和研究不足。
2.1 作業(yè)場(chǎng)所降溫
目前降低人體熱應(yīng)激最佳措施仍是空調(diào)設(shè)備,但是其僅適用于室內(nèi)作業(yè)人員。對(duì)于戶外作業(yè)人員,主要的降溫方式有使用強(qiáng)力風(fēng)扇,穿著冰馬甲及在身體周圍放置冰塊以冷卻周圍空氣等,如圖2所示。由于傳熱原理和防護(hù)服的密閉性,風(fēng)扇降溫僅在外界環(huán)境溫度低于人體皮膚溫度時(shí)起到一定作用。對(duì)于極端高溫環(huán)境,風(fēng)扇降溫不再發(fā)揮作用[18]。另外,穿著冰馬甲僅會(huì)帶來(lái)短暫的冷卻效果,而采用冰塊冷卻周圍大環(huán)境帶來(lái)的冷卻效果更是有限。
除上述方式外,正壓醫(yī)用防護(hù)服裝是目前采用的一種主動(dòng)式的氣冷降溫方式。當(dāng)前新型正壓防護(hù)服裝被用來(lái)降低醫(yī)護(hù)人員在高溫作業(yè)環(huán)境下的熱應(yīng)激,其作用原理是促進(jìn)人體和服裝微環(huán)境之間的空氣流動(dòng),使皮膚表面汗液蒸發(fā)帶走熱量[19]。目前有兩種類型的正壓防護(hù)服,即自然風(fēng)冷卻服和壓縮冷空氣制冷服裝[20]。圖3為中國(guó)駝人集團(tuán)研發(fā)的醫(yī)用正壓防護(hù)服,其中冷空氣由小型空氣壓縮機(jī)產(chǎn)生,通過(guò)管道送入腰部新風(fēng)系統(tǒng)(裝有過(guò)濾裝置),接著通過(guò)軟管進(jìn)入人體和服裝微環(huán)境。另外,將空氣壓縮機(jī)與新風(fēng)系統(tǒng)分離,此防護(hù)服可作為自然風(fēng)冷卻服使用。目前該防護(hù)服在河南、湖北、海南等多個(gè)地區(qū)的室外核酸檢測(cè)現(xiàn)場(chǎng)對(duì)醫(yī)護(hù)人員開(kāi)展了小范圍的穿著實(shí)驗(yàn),發(fā)現(xiàn)該防護(hù)服可顯著提高穿著舒適性。然而由于價(jià)格昂貴且結(jié)構(gòu)復(fù)雜,該類正壓防護(hù)服裝并未得到廣泛應(yīng)用。另外,缺少對(duì)該類防護(hù)服降溫效果的主客觀評(píng)價(jià)及著裝后運(yùn)動(dòng)靈活性、穿脫便利性等方面的工效性評(píng)價(jià),未來(lái)研究需要通過(guò)熱生理實(shí)驗(yàn)進(jìn)行測(cè)試與評(píng)價(jià)。
2.2 異質(zhì)結(jié)構(gòu)面料
異質(zhì)結(jié)構(gòu)面料(Janus)是指雙面潤(rùn)濕性能不同的單向?qū)衩媪希淇梢詫⑵つw表面的汗液轉(zhuǎn)移到外界環(huán)境,減少人體穿著時(shí)的濕黏感,同時(shí)汗液蒸發(fā)會(huì)帶走熱量,提升人體舒適性[21]。另外,Janus面料可以阻止環(huán)境液體的滲透[21]。王潔等[22]采用泡沫整理法對(duì)聚丙烯紡黏—熔噴—紡黏非織造布(SMS)的一面采用親水整理,另一面進(jìn)行“三拒一抗”整理(即拒水、拒油、拒酒精和抗靜電),并發(fā)現(xiàn)整理后的SMS獲得了良好的單向?qū)裥Ч?。任祺等?3]采用親水性整理劑Hansi QS-CONC對(duì)SMS非織造布進(jìn)行單面親水整理,整理后的材料透濕量從整理前的2.034 kg/(m2·d),提升到2.615 kg/(m2·d),透濕性得到顯著提升。Zhang等[24]制備了一種由聚乳酸(PLA)/低熔聚乳酸(LPLA)和疏水熱塑性聚氨酯(TPU)組成的新型Janus無(wú)紡布,富含親水性基團(tuán)的PLA作為面料內(nèi)層表現(xiàn)出優(yōu)異的內(nèi)吸水性,疏水的TPU作為外層可有效提高非織造布的機(jī)械性能和耐磨性,實(shí)現(xiàn)了非織造布內(nèi)層吸收(防止液體回流)和外層保護(hù)性能,可作為醫(yī)用防護(hù)服裝的候選材料。Shou等[25]開(kāi)發(fā)了一種具有不對(duì)稱性孔徑的全親水性射流二極管面料(AHFD),液體可以自由地從該面料一側(cè)吸向另一側(cè),但反方向的輸送被阻塞。該面料可用于防護(hù)服,它允許人體汗液排出但阻擋有毒液體以提供舒適和保護(hù)。
Janus面料有望作為醫(yī)用防護(hù)服裝主體材料以提升其熱濕舒適性。然而目前更多的是對(duì)該面料的基礎(chǔ)熱物理性質(zhì)測(cè)試,即水氣傳遞能力和隔熱性測(cè)試,缺少對(duì)其實(shí)際穿著效果評(píng)價(jià)。未來(lái)需要將此面料制作成醫(yī)用防護(hù)服裝,開(kāi)展人體穿著實(shí)驗(yàn),通過(guò)人體熱生理指標(biāo)變化及主觀感覺(jué)進(jìn)行評(píng)判。
2.3 超吸水材料
超吸水材料能吸收自身幾十至幾百倍的水分[26],用于服裝可以吸收大量人體皮膚表面汗液,從而提升人體舒適性[27]。目前,超吸水材料在醫(yī)用防護(hù)領(lǐng)域的研究主要是超吸水纖維和超吸水膜兩種形態(tài)。Sivri等[28]使用聚乙烯醇和高吸水聚合物成比例混合的溶液,采用靜電紡絲法制備了高吸水納米纖維,并將其涂覆在口罩上以改善口罩的防護(hù)性和舒適性。通過(guò)吸液能力和透氣性測(cè)試,發(fā)現(xiàn)該納米纖維涂層增強(qiáng)了口罩吸收汗液的能力,提高了佩戴舒適性,但同時(shí)納米纖維堵塞了口罩材料纖維孔隙,降低了透氣性。Yang等[29]采用濕法紡絲法制備了一種新型醫(yī)用防護(hù)服裝復(fù)合面料(圖4),其外層為聚丙烯酸—丙烯酰胺/聚乙烯醇纖維、竹漿纖維和乙丙烯纖維層合的超吸水無(wú)紡布,內(nèi)層為抗靜電的高強(qiáng)度聚丙烯無(wú)紡布。通過(guò)實(shí)驗(yàn)發(fā)現(xiàn)該防護(hù)服面料具備優(yōu)異的水分吸收能力,其最大吸濕率達(dá)到1.04 g/h,顯著高于傳統(tǒng)防護(hù)服面料的0.53 g/h,并且其透濕系數(shù)達(dá)到12 638.5 g/(m2·d),為傳統(tǒng)面料的3.1倍。Yang等[30]制備了一種可用于醫(yī)用防護(hù)服裝熱管理的超吸水性鋅—聚乙烯醇復(fù)合薄膜,并將40 cm×40 cm的該薄膜貼于醫(yī)用防護(hù)服裝背部?jī)?nèi)面進(jìn)行了出汗假人實(shí)驗(yàn)。實(shí)驗(yàn)發(fā)現(xiàn),該薄膜可降低防護(hù)服內(nèi)部40%的濕度;降低熱指數(shù)到41 ℃以下,從而降低醫(yī)護(hù)人員中暑的可能性;還可以顯著降低防護(hù)服蒸發(fā)阻力,以增強(qiáng)蒸發(fā)冷卻來(lái)獲得更多的熱損失。
目前超吸水材料作為主體面料或者涂覆層可以提高防護(hù)服面料的透濕性、透氣性,但未研究其耐用性,如吸濕后的機(jī)械性能下降等。另外,未研究吸收材料制成的服裝對(duì)人體造成的熱生理和心理感受。
2.4 輻射降溫面料
輻射降溫面料概念最早由Tong等[31]于2015年提出,其是由低紅外反射率和高紅外透射率材料層合而成,并將人體輻射熱量直接傳輸?shù)酵饨绛h(huán)境中來(lái)提供被動(dòng)降溫。目前,學(xué)者們探索了應(yīng)用于醫(yī)用防護(hù)服裝的輻射降溫面料制備及其降溫效果評(píng)價(jià)[32-33]。吳欽鑫等[32]采用靜電紡絲法制備了具有輻射降溫功能的二氧化硅/聚偏氟乙烯(SiO2/PVDF)納米纖維中間層,并通過(guò)熱壓法將其夾在兩層非織造布之中,制備了輻射降溫納米纖維醫(yī)用防護(hù)服裝面料。同時(shí),將市售防護(hù)服腋下兩側(cè)面料替換為新型防護(hù)服面料并開(kāi)展了人體穿著實(shí)驗(yàn),發(fā)現(xiàn)實(shí)驗(yàn)結(jié)束時(shí)新型防護(hù)服面料將人體與服裝微環(huán)境溫濕度分別降低了約2 ℃和5%。Zhang等[33]針對(duì)易暴露于極端高溫環(huán)境下的特殊行業(yè)人員和醫(yī)務(wù)工作者,采用靜電紡絲和浸漬涂層工藝合成了一種吸濕被動(dòng)冷卻分層超織物,其同時(shí)具備紅外輻射冷卻和水分蒸發(fā)冷卻性能,其作用原理如圖5所示。通過(guò)熱壓法將該超織物與紡黏無(wú)紡布層合,制備了一種防護(hù)性超織物,并通過(guò)人體穿著實(shí)驗(yàn)發(fā)現(xiàn)相較于傳統(tǒng)醫(yī)用防護(hù)服裝,該織物制成的服裝可以顯著降低衣下空氣層的溫度和相對(duì)濕度。另外,有學(xué)者制備了兼具水分管理性能的輻射降溫面料[33-34]。如Hu等[34]使用聚丙烯腈和二氧化硅納米顆粒制備了雙層納米多孔聚乙烯膜,并發(fā)現(xiàn)該材料同時(shí)具有輻射冷卻能力和各向異性潤(rùn)濕性能,作用原理如圖6所示。通過(guò)人工皮膚模擬設(shè)備測(cè)試了其紅外輻射冷卻性能,并發(fā)現(xiàn)在25.1 ℃的環(huán)境溫度下,相較于棉纖維面料和特衛(wèi)強(qiáng)材料,該材料覆蓋的人工皮膚溫度顯著降低,同時(shí)該材料通過(guò)了防水和細(xì)顆粒物阻斷測(cè)試。該具有水分管理性能的輻射降溫面料有望應(yīng)用于醫(yī)用防護(hù)服裝,以提高醫(yī)護(hù)人員熱濕舒適感。
目前研究通過(guò)人體穿著實(shí)驗(yàn)證明紅外輻射降溫面料可以顯著降低衣下空氣層溫度,但未能給出直接反應(yīng)人體熱濕舒適性的客觀生理指標(biāo),如皮膚溫度或者主觀感受指標(biāo)。另外,多數(shù)研究未探索輻射降溫面料的其他重要指標(biāo),如機(jī)械性能等。
2.5 相變冷卻降溫
相變材料(PCM)是指隨外界溫度變化而改變狀態(tài)并能產(chǎn)生潛熱的物質(zhì),其由固態(tài)變?yōu)橐簯B(tài)或由液態(tài)變?yōu)楣虘B(tài)時(shí)會(huì)吸收或釋放大量的潛熱而物質(zhì)溫度不變[35]。目前PCM應(yīng)用于服裝面料主要有三種途徑,即將PCM植入纖維內(nèi)部、將PCM涂敷于織物表面及將PCM以塊狀的形式置于服裝多個(gè)位置[36]。研究發(fā)現(xiàn),PCM的制冷/加熱效果顯著取決于其質(zhì)量和覆蓋面積[37]。前兩種途徑無(wú)法在纖維或面料內(nèi)加入大量的PCM,因而獲得的PCM面料降溫效果不顯著,而將塊狀PCM加入服裝內(nèi)可以提供顯著的制冷量。Korte等[38]設(shè)計(jì)了一款穿在醫(yī)用防護(hù)服裝下的相變材料降溫背心,前后分別有16個(gè)和20個(gè)口袋,每個(gè)口袋用于裝入相變材料包。通過(guò)實(shí)地測(cè)量17位醫(yī)護(hù)人員穿著該背心作業(yè)時(shí)的生理指標(biāo)和主觀感受,發(fā)現(xiàn)該降溫背心可顯著降低人體核心溫度和心率,改善熱舒適和熱感覺(jué)水平。另外,該背心在使用前只需放在低溫冰箱里激活,使用完消毒后再放入低溫冰箱即可,其結(jié)構(gòu)及使用流程如圖7所示。Reinertsen等[39]使用十水硫酸鈉和芒硝結(jié)晶兩種PCM制作了降溫背心,通過(guò)人體穿著實(shí)驗(yàn)證明了該背心可改善醫(yī)用防護(hù)服裝帶給人的熱感覺(jué)、熱舒適性及濕感覺(jué)。
雖然學(xué)者們發(fā)現(xiàn)融合相變材料包的服裝在一定程度上降低了人體熱應(yīng)激,提高了人體舒適性,但存在著質(zhì)量大、靈活性低、透氣性差等問(wèn)題[40],導(dǎo)致一部分的冷卻效果被抵消。并且相變材料冷卻持續(xù)時(shí)間較短,往往需要通過(guò)增加PCM質(zhì)量以延長(zhǎng)冷卻時(shí)間[41],未來(lái)可以將熔化溫度不同的PCM結(jié)合使用以減輕背心質(zhì)量[42],并進(jìn)行人體穿著實(shí)驗(yàn)評(píng)估PCM冷卻背心在質(zhì)量、運(yùn)動(dòng)便利性等方面對(duì)舒適性及冷卻效果的影響。
3 緩解人體熱應(yīng)激的新材料與技術(shù)
除上述針對(duì)醫(yī)用防護(hù)服裝的設(shè)計(jì)外,還有應(yīng)用于其他功能服裝的緩解人體熱應(yīng)激的新材料與技術(shù)。通過(guò)分析它們的作用原理、工效性能及實(shí)用性等,并思考其在醫(yī)用防護(hù)服裝上的有效性及可用性,選擇了高導(dǎo)熱材料、熱電冷卻材料和液態(tài)冷卻服裝三類先進(jìn)材料和技術(shù)進(jìn)行闡述,為開(kāi)發(fā)新型醫(yī)用防護(hù)服裝以緩解人體熱應(yīng)激提供思路。
3.1 高導(dǎo)熱材料
高導(dǎo)熱材料的導(dǎo)熱系數(shù)遠(yuǎn)高于空氣的導(dǎo)熱系數(shù),其可以通過(guò)熱傳導(dǎo)將人體熱量傳遞到外界環(huán)境,從而避免熱應(yīng)激[43]。近年來(lái)高導(dǎo)熱材料如石墨烯和氮化硼常被用作個(gè)體熱管理材料,它們通常被配制成聚合物溶液涂布到基材,或作為填料放置于基材纖維的空隙中,得到復(fù)合材料(膜),實(shí)現(xiàn)對(duì)基材的改性。Guo等[44]使用涂布的方法制備了一種柔性/可折疊、可穿戴的超薄石墨烯紙,如圖8所示。其可在7 s內(nèi)通過(guò)人體向環(huán)境的熱傳遞提供被動(dòng)冷卻,冷卻效果優(yōu)于普通棉織物,并且效果隨著厚度的增加會(huì)更加明顯。同時(shí)它具備優(yōu)良的耐久性,可抗彎曲周期超過(guò)500次,洗滌時(shí)間超過(guò)1 500 min,這表明了其在可穿戴個(gè)人熱管理方面的潛力。Bonetti等[45]將石墨烯納米片(GNPs)作為導(dǎo)電填料分散在聚氨酯(PU)基體中制備了納米復(fù)合聚合物膜,該材料可以很容易地與織物耦合,獲得熱舒適性增強(qiáng)的紡織品和服裝。通過(guò)材料熱表征證實(shí)GNPs顯著提高了PU的導(dǎo)熱率(最高達(dá)471%),并通過(guò)模擬運(yùn)動(dòng)員在室外有氧運(yùn)動(dòng)狀態(tài)下的前臂人體模型驗(yàn)證了開(kāi)發(fā)的納米復(fù)合膜和紡織品的散熱效果。Soong等[46]使用機(jī)械混合技術(shù)將石墨烯納米片(GNPs)和氮化硼(BN)填料分散到熱塑性聚氨酯(TPU)基薄膜中,然后將其復(fù)合成多層結(jié)構(gòu),獲得了明顯高于純TPU膜(2 844%)的高導(dǎo)熱系數(shù)、良好的抗彎疲勞和耐洗滌性。將該復(fù)合薄膜放置于T恤內(nèi)部進(jìn)行人體穿著實(shí)驗(yàn)并測(cè)量其冷卻效果,發(fā)現(xiàn)該復(fù)合膜可以增強(qiáng)主動(dòng)冷卻源周圍冷空氣的擴(kuò)散,因而可以更快、更大幅度地降低皮膚溫度。
高導(dǎo)熱材料在醫(yī)用防護(hù)服裝上的應(yīng)用,可以參考以上涂布和填料的方式實(shí)現(xiàn)對(duì)醫(yī)用防護(hù)服裝用非織造材料的改性。當(dāng)外界環(huán)境溫度低于人體皮膚溫度并達(dá)到一定程度時(shí),高導(dǎo)熱材料可以有效促進(jìn)人體向外界的散熱量。未來(lái)研究仍需要開(kāi)展人體穿著實(shí)驗(yàn)評(píng)估其穿著舒適性、降溫有效性及環(huán)境適用性。另外石墨烯還具有優(yōu)異的抗菌性能,目前已有人用其制備抗菌抗病毒的口罩和防護(hù)服,其優(yōu)異的強(qiáng)度也可以大大提高織物的力學(xué)性能,使防護(hù)服面料抗洗滌性能持久,在重復(fù)性使用醫(yī)用防護(hù)服裝中有著良好的應(yīng)用潛力。
3.2 熱電冷卻材料
隨著可穿戴電子設(shè)備的快速發(fā)展,以及全球變暖、能源危機(jī)等環(huán)境問(wèn)題下對(duì)節(jié)能要求的不斷提高[47],可以回收人體熱量實(shí)現(xiàn)自供電的熱電材料在個(gè)人熱管理中得到了廣泛研究[48]。熱電冷卻材料可以通過(guò)塞貝克效應(yīng)實(shí)現(xiàn)溫差發(fā)電,再通過(guò)帕爾貼效應(yīng)利用電能制冷[49]。它的性能可通過(guò)熱電優(yōu)值(ZT)量化,ZT越大,表示塞貝克系數(shù)越大,電導(dǎo)率越高,熱導(dǎo)率越低,冷卻效果越好。目前在可穿戴熱電個(gè)人熱管理材料中,最常采用的是近室溫?zé)犭姴牧?,主要包括以Bi2Te3基為主的半導(dǎo)體材料、碳納米管、聚苯乙烯磺酸鹽等[50],其被用于制備柔性熱電器件,包括熱電薄膜、熱電紗線/纖維/織物及基于柔性彈性體基底的塊狀熱電元件。Li等[51]制備了一種柔性紅外透明Bi2Te3碳納米管混合熱電薄膜,其在370 K室溫下產(chǎn)生了約0.23的最大熱電優(yōu)值,并具有極好的柔韌性和約16%的最大紅外透明度,開(kāi)辟了一種具有主動(dòng)和被動(dòng)雙重冷卻能力的高效熱電冷卻方法。Zheng等[52]結(jié)合簡(jiǎn)易冷壓及超高溫快速退火技術(shù)制備了三元同軸串珠狀Bi2Te3基柔性熱電紗線,并利用紡織機(jī)半自動(dòng)地制造了一種高度機(jī)械穩(wěn)定、可拉伸、透氣和可清洗的編織型熱電織物,如圖9(a)所示。通過(guò)在靜止空氣中(環(huán)境溫度26 ℃、相對(duì)濕度60%)對(duì)其進(jìn)行手臂佩戴測(cè)試,發(fā)現(xiàn)該織物表現(xiàn)出較為明顯的固態(tài)制冷效果,如圖9(b)所示。Hong等[53]設(shè)計(jì)了第一款具有長(zhǎng)期主動(dòng)冷卻效果的微型可穿戴熱電器件,其內(nèi)部結(jié)構(gòu)如圖10所示。此舉創(chuàng)新性地采用了雙彈性體層的設(shè)計(jì),將具備高熱電優(yōu)值的剛性無(wú)機(jī)柱狀熱電材料夾在可拉伸彈性體片之間,減少了通過(guò)熱電設(shè)備的熱泄漏,提供了高冷卻性能。該設(shè)備經(jīng)人體手臂穿戴實(shí)驗(yàn),得到了超過(guò)10 ℃的冷卻效果,且具有高節(jié)能性。
柔性熱電器件與傳統(tǒng)的液冷、氣冷等主動(dòng)冷卻方式相比,無(wú)噪聲,更為靈活、輕便、舒適,且可以從周圍環(huán)境或人體中收集能量,維持設(shè)備電能供應(yīng),極大地節(jié)省了能源。其中熱電紗線/纖維可與其他織物結(jié)合編織成三維熱電織物,若制成背心穿戴在醫(yī)用防護(hù)服裝內(nèi)部或者外部,不僅可以利用熱傳導(dǎo)散熱機(jī)制實(shí)現(xiàn)大面積熱量收集,同時(shí)還可以利用織物較強(qiáng)彈性和應(yīng)變力,滿足人體動(dòng)作帶來(lái)的皮膚應(yīng)變,且可洗滌重復(fù)使用。盡管柔性熱電器件在緩解醫(yī)用防護(hù)服裝熱應(yīng)激方面有著較大應(yīng)用潛力,但目前的研究尚屬于初期階段,高昂的成本、可穿戴應(yīng)用方面較低的靈活性及復(fù)雜的制造工藝都有待進(jìn)一步改善[54],并且缺乏人體穿著實(shí)驗(yàn)評(píng)估其降溫的有效性、穿著的舒適性等。
3.3 液態(tài)冷卻服裝
液態(tài)冷卻服裝通過(guò)內(nèi)置管道中循環(huán)的冷卻液帶走人體熱量,從而實(shí)現(xiàn)冷卻效果。該服裝概念由比林漢姆于1958年首次提出,并在1962年由皇家飛機(jī)制造廠開(kāi)發(fā)出了最初的水冷服原型[55]。最著名的水冷服于1970年的阿波羅號(hào)上使用,由彈力內(nèi)衣和縫在其內(nèi)的覆蓋軀干和腿部的40根透明塑料管組成。冷卻水從腰部的歧管分配到各個(gè)小管中流過(guò)服裝,并在腰部返回收集[56]。Xu等[57]設(shè)計(jì)了一種基于熱電制冷的新型男士便攜式冷卻服,其采用半導(dǎo)體熱電冷卻系統(tǒng)為冷卻液提供制冷電力,皮膚表面的溫度通過(guò)輸送冷卻液的金屬毛細(xì)管冷卻。通過(guò)實(shí)驗(yàn)發(fā)現(xiàn)在30℃的環(huán)境溫度下,冷卻服可快速降低服裝微氣候溫度。Zheng等[58]采用人體溫度調(diào)節(jié)模型與熱舒適模型相結(jié)合的方法研究了液冷服裝各種設(shè)計(jì)因素對(duì)冷卻性能的影響,發(fā)現(xiàn)與連續(xù)冷卻模式相比,高頻間歇冷卻模式(如5 min的時(shí)間周期)能夠以更少的能耗緩解人體熱應(yīng)激。Zhang等[59]建立了熱電冷卻液冷服裝與環(huán)境和人體之間的傳熱模型,分析了電壓和流量對(duì)冷卻性能的影響,發(fā)現(xiàn)熱電冷卻器的工作電壓對(duì)冷卻效果的影響比管內(nèi)液體的流速更顯著,并且存在最優(yōu)工作電壓,在最優(yōu)工作電壓下,冷卻效果隨著流量的增大而增大。
液冷服裝因冷卻液體較高的比熱容和熱導(dǎo)率,可以實(shí)現(xiàn)顯著的冷卻效果,為穿著者提供較好的熱舒適性[55],因此是目前較常用的一種有效冷卻方式。對(duì)于醫(yī)用防護(hù)服裝,穿在防護(hù)服內(nèi)部、緊貼人體的液冷背心可以顯著促進(jìn)人體傳導(dǎo)散熱量。然而其主要問(wèn)題是冷卻液質(zhì)量會(huì)增加人體負(fù)擔(dān)及輸送冷卻液管道可能會(huì)妨礙人體活動(dòng),因此未來(lái)研究應(yīng)以提高人體舒適性和運(yùn)動(dòng)便利性為目標(biāo),選擇適宜的冷卻液循環(huán)量、更為柔軟的管道材料,以及合理的管道排布、冷卻液流速和冷卻液循環(huán)頻率等,并通過(guò)人體穿著實(shí)驗(yàn)進(jìn)行評(píng)價(jià)。
4 緩解人體熱應(yīng)激的醫(yī)用防護(hù)服裝研究趨勢(shì)
根據(jù)當(dāng)前醫(yī)用防護(hù)服裝存在的熱濕舒適性問(wèn)題,以及緩解熱應(yīng)激的材料、技術(shù)和實(shí)驗(yàn)研究情況,本文提出以下4點(diǎn)緩解人體熱應(yīng)激的醫(yī)用防護(hù)服裝研究趨勢(shì)。
4.1 提高主動(dòng)冷卻設(shè)備的工效性能
主動(dòng)冷卻方式包括液冷、氣冷等,相較于被動(dòng)冷卻方式(即無(wú)外接電源的制冷方式)具有更有效的制冷效果,然而這種方式需在服裝上安裝一定體積質(zhì)量的設(shè)備,增加人體負(fù)擔(dān),不方便人體運(yùn)動(dòng)。因此,需要不斷改善并開(kāi)發(fā)更加輕便、柔軟的主動(dòng)冷卻設(shè)備,提高其工效性,從而獲得更好的冷卻效果和穿著體驗(yàn)。
4.2 擴(kuò)展調(diào)溫新材料與技術(shù)在醫(yī)用防護(hù)服裝上的應(yīng)用
目前已有研究發(fā)現(xiàn)異質(zhì)結(jié)構(gòu)面料、超吸水材料、輻射降溫面料、相變材料等可以顯著改善醫(yī)用防護(hù)服裝熱濕舒適性,也討論了高導(dǎo)熱材料、熱電冷卻材料和液態(tài)冷卻方式等在人體熱管理方面的應(yīng)用潛力。調(diào)溫新材料和技術(shù)有望應(yīng)用于醫(yī)用防護(hù)服裝,改善人體熱濕舒適性并降低人體熱應(yīng)激,但通常存在制備工藝較為復(fù)雜、制造成本高等問(wèn)題。醫(yī)用防護(hù)服裝作為防護(hù)耗材,新材料與技術(shù)在其上的應(yīng)用,除了需要考慮冷卻效果、工效性能等,生產(chǎn)周期和成本也是非常重要的因素。部分材料與技術(shù)可以制成單獨(dú)的降溫服裝穿著于人體和醫(yī)用防護(hù)服裝之間,如相變材料、熱電冷卻材料和液冷服裝,這類降溫服裝可以反復(fù)使用,其成本將不再是顯著問(wèn)題。而另一部分材料需要作為醫(yī)用防護(hù)服裝主體面料使用,如異質(zhì)結(jié)構(gòu)面料、輻射降溫面料和高導(dǎo)熱材料等,考慮到加工難度和成本,這類材料更適合應(yīng)用于重復(fù)性使用醫(yī)用防護(hù)服裝。重復(fù)性使用醫(yī)用防護(hù)服裝通??梢苑磸?fù)使用10次以上[60],因此這類材料在重復(fù)性使用醫(yī)用防護(hù)服裝上的應(yīng)用應(yīng)成為研究重點(diǎn)。另外,未來(lái)應(yīng)通過(guò)材料或設(shè)備的測(cè)試及人體穿著實(shí)驗(yàn),測(cè)量防護(hù)服的冷卻效果、穿著舒適性、運(yùn)動(dòng)便利性等,同時(shí)考慮生產(chǎn)難度、成本等,全方位評(píng)估它們?cè)卺t(yī)用防護(hù)服裝上的應(yīng)用可行性。
4.3 建立緩解人體熱應(yīng)激的醫(yī)用防護(hù)服裝設(shè)計(jì)方法和流程
目前國(guó)內(nèi)外缺少針對(duì)緩解人體熱應(yīng)激的醫(yī)用防護(hù)服裝的系統(tǒng)設(shè)計(jì)方法和流程。緩解人體熱應(yīng)激的醫(yī)用防護(hù)服裝設(shè)計(jì)方法和流程可以參考Gupta[61]提出的“五步法”功能服裝設(shè)計(jì)方法,即用戶研究、用戶需求、服裝設(shè)計(jì)、服裝制作以及測(cè)試與分析,并以Goldman[62]提出的“4F”原則(功能性、舒適性、合體性和時(shí)尚性)為醫(yī)用防護(hù)服裝主要設(shè)計(jì)原則,在此基礎(chǔ)上引入實(shí)用性和經(jīng)濟(jì)型等指標(biāo)進(jìn)行設(shè)計(jì)。在具體操作上,可以引入一些新興的設(shè)計(jì)方法和技術(shù),實(shí)現(xiàn)醫(yī)用防護(hù)服裝設(shè)計(jì)的高效、環(huán)保。如采用計(jì)算機(jī)輔助技術(shù)選擇防護(hù)服面料和款式,以實(shí)現(xiàn)防護(hù)服熱濕舒適性及壓力舒適性的優(yōu)化設(shè)計(jì);利用動(dòng)作捕捉和身體測(cè)繪技術(shù)獲取人體各部位活動(dòng)變化量、皮膚應(yīng)變量及人體尺寸數(shù)據(jù)來(lái)進(jìn)行防護(hù)服放松量與結(jié)構(gòu)設(shè)計(jì),提高防護(hù)服舒適性和運(yùn)動(dòng)靈活性;引入模塊化設(shè)計(jì)思維到防護(hù)服設(shè)計(jì)開(kāi)發(fā)階段,對(duì)設(shè)計(jì)元素進(jìn)行拆分組合來(lái)更快獲得設(shè)計(jì)目標(biāo),節(jié)約時(shí)間的同時(shí)顯著提升設(shè)計(jì)結(jié)果。通過(guò)建立緩解人體熱應(yīng)激的醫(yī)用防護(hù)服裝設(shè)計(jì)方法和流程,可以推動(dòng)相關(guān)標(biāo)準(zhǔn)的完善,提高醫(yī)用防護(hù)服裝舒適性。
4.4 開(kāi)展緩解人體熱應(yīng)激的醫(yī)用防護(hù)服裝測(cè)試與評(píng)價(jià)
目前關(guān)于緩解人體熱應(yīng)激的材料測(cè)試大多局限于材料本身,缺少將其制成服裝進(jìn)行實(shí)際穿著效果評(píng)價(jià),特別是被動(dòng)冷卻材料。另外,缺少對(duì)材料實(shí)際制冷效果的評(píng)價(jià)體系。未來(lái)研究需要借助功能服裝的測(cè)試與評(píng)價(jià)方法對(duì)醫(yī)用防護(hù)服裝熱濕舒適性及工效性進(jìn)行評(píng)價(jià),即五級(jí)評(píng)價(jià)方法:織物的物理分析、出汗暖體假人測(cè)試、人體穿著實(shí)驗(yàn)、有限現(xiàn)場(chǎng)穿著實(shí)驗(yàn)和大規(guī)模的現(xiàn)場(chǎng)穿著實(shí)驗(yàn)。在人體穿著實(shí)驗(yàn)中,可以采用腦電和面部情緒識(shí)別等技術(shù)直觀反映人體認(rèn)知和情緒狀態(tài)的技術(shù),獲取被試更準(zhǔn)確的主觀感受;還可以利用動(dòng)作捕捉技術(shù)獲取人體運(yùn)動(dòng)時(shí)面料在人體上的位移數(shù)據(jù),結(jié)合被試主觀感受評(píng)價(jià)防護(hù)服工效性。多級(jí)實(shí)驗(yàn)的反復(fù)驗(yàn)證,多種評(píng)價(jià)方法的結(jié)合,可以更準(zhǔn)確地掌握醫(yī)用防護(hù)服裝的舒適性和工效性,評(píng)估設(shè)計(jì)的有效性并提供優(yōu)化建議。
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Research progress and trend of medical protective clothing to alleviate human thermal stress
LU Wenyue, YAN Yuxin, CHEN Xing, SONG Wenfang
(College of Art & Design, Guangdong University of Technology, Guangzhou 510090, China)
Abstract:Medical protective clothing (MPC) is essential for healthcare workers and those entering areas at risk of infection. It could effectively block substances such as bacteria, viruses, harmful liquids and particles. However, to ensure protection, the MPC fabric generally has numerous small apertures and also does not absorb water, resulting in its poor thermal and moisture comfort property. The heat and sweat generated by healthcare workers in MPC could not be dissipated to the ambient environment, which may destroy the body thermal balance, increase the risk of thermal stress and damage their physical health, psychological state and performance. The wide spread of COVID-19 around the world makes the poor thermal and moisture comfort property of MPC more prominent. Therefore, the investigation on MPC to alleviate human thermal stress has become the focus of current and future research.
To understand the current research progress and future trend in the development of MPC to reduce human thermal stress, and to provide solid suggestions for the design of MPC, we firstly summarized the materials, styles and comfort properties of MPC specified in current standards, and pointed out that human demand for thermal and wet comfort could not be satisfied in MPC following the current standards. Then, we described the research progress of MPC to relieve human thermal stress from the methods of workplace cooling and those studied by academic research. Workplace cooling includes using powerful air fans, ice, ice vests and medical positive-pressure protective suits. Among the various cooling strategies, medical positive-pressure protective suits are the most effective, but they are not widely applied in practice due to their high cost. In terms of the methods studied by academic research, we summarized the research progress and gaps in the application of four types of temperature-regulating materials on MPC, i. e., Janus fabrics, superabsorbent materials, radiant cooling materials and phase change materials. The cooling benefits of these materials have been proved by measuring the two-dimensional fabrics made from them, but three-dimensional clothing made from these materials should be evaluated in future by using human trials. Finally, we summarized three types of advanced materials and technologies that have great potential to be used in MPC from other functional clothing, i. e., highly thermal-conductive materials, thermoelectric-cooling materials and liquid cooling garments. We described the materials in terms of their properties, cooling principles, cooling effects and application concept in MPC to provide solid suggestions for the development of novel MPC to alleviate human thermal stress.
With the frequent occurrence of high-temperature weather, research on alleviating human thermal stress has been continuously enriched in recent years. After the outbreak of COVID-19, the thermal and wet comfort property and ergonomic performance of MPC have gained more attention, but there are still many research deficiencies. Based on the current problems of MPC, materials and technologies used in MPC to alleviate human thermal stress, four research trends were proposed: improving the ergonomic performance of active cooling equipment; expanding the application of new temperature-regulating materials and technologies on MPC; establishing scientifical design methods and processes for MPC to relieve human thermal stress; carrying out testing and evaluation of MPC to alleviate human thermal stress. By summarizing the current research progress of MPC that relieves human thermal stress, the defects of current research were identified, and future development directions were proposed. The study is expected to provide solid suggestions for the development of MPC with excellent thermal and wet comfort property and ergonomic performance.
Key words:medical protective clothing; thermal stress; thermal and wet comfort; temperature-regulating materials and technologies; ergonomic performance; design and evaluation of clothing