新世代呼吸防護具的研發

Abstract

第二章: 呼吸防護具其繫帶的鬆緊程度影響了密合程度，然而，有關繫帶張力對過濾面體(FFRs, Filtering Facepiece Respirators)密合度的影響的文獻仍十分有限，且大多數FFRs的繫帶採固定長度之設計。因此，本研究旨在探討不同繫帶材質之面體密合度，找出最適條件之繫帶材質與張力，也一併對不同人頭大小、皮膚硬度進行探討。在本研究中，使用3D列印機打印出由聚乳酸製作的標準中國頭型（小、中、大型）。使用張力計（Handy Digital Force Gauge，Algol，HF-1，Japan）進行繫帶張力的量測。使用冷凝顆粒計數器（PortaCount，TSI Inc.，St.Paul，MN，USA）測量FFRs內部和外部的顆粒濃度。 由研究結果顯示，將FFRs佩戴於中國標準人頭，上繫帶張力（2.03~5.74 N）基本上都高於下繫帶張力（1.18~4.55 N），且原廠設定之繫帶張力並沒有隨著FFRs重量的增加而增加，這可能會減少面體對呼吸道的保護。對於典型的FFRs繫帶，張力在前一個小時內從4.6到3.5 N迅速下降，且在前20分鐘內，張力會發生最顯著的衰減。在劇烈變化期後，下降趨勢減弱。因此實驗皆以20分鐘為周期進行測量。大多數繫帶在前20分鐘內有20 ％的衰減。由假人頭持續密合度測試之研究結果指出密合係數隨時間衰減，可能是由於繫帶張力的衰減。因此需要具有更穩定的張力特性繫帶以提供更恆定的呼吸保護。繫帶張力穩定性取決於紗支數，膠條數量決定了初始張力，故會建議市售的FFRs使用張力特性更穩定之繫帶高紗支數），以提供長期且穩定的密合。此外，在前10分鐘密合係數會發生最顯著的衰減，因此建議受試者佩戴面體十分鐘後再進行密合度測試。本研究還比較不同的皮膚硬度，結果表明較軟的臉部有較好的密合度。在臉部硬度相同的情況下，較大的頭型具有更好的密合性。如果面體不適合面部，繫帶張力對於密合之優化效果有限。適合臉部的面體則可以藉由改變繫帶張力增加密合情形，因此會建議繫帶改為可調式，僅需較少之繫帶張力即可達良好密合與舒適性。目前市售面罩專為西方人設計，故東方人佩戴密合度有普遍偏低的情況，理想的情況是每個人都有自己的客製化口罩，在這樣情況下可以實現最小的繫帶張力與最高舒適性。 第三章: 市售口罩皆為固定規格，無法適用所有人之臉型，不適合之口罩將會導致空氣污染物從不密合處洩漏進入呼吸區並對人體造成害。若是佩戴與其臉部輪廓完全密合之客製化口罩，可以使用最低的繫帶張力達到最好的密合效果及舒適性，故本研究將利用3D掃描及3D列印方法製作客製化面體，解決呼吸防護中最棘手的密合度問題。 製作客製化面體需利用3D掃描及3D列印之技術，故本研究分為三個部分，第一部分需先利用假人頭評估市售掃描機台之掃描偏差，使用市售7款3D掃描機台進行假人頭掃描，藉由3D列印機台列印出中國標準人頭後，使用掃描機台進行量測，接著藉由軟體進行圖檔之比對，個別將掃描結果與原始圖檔進行誤差分析。第二部分為評估人體臉部在掃描期間移動所造成之影響，由於手持式掃描儀所需之掃描時間較長，為了評估這期間人臉變動所造成之誤差，掃描了10位真人，將手持式與固定式掃描儀之掃描結果進行誤差比較。第三部分則使用3D掃描系統建立三維臉部模型，接著使用電腦輔助設計computer aided design (CAD)建構出口罩模型，並3D列印印出客製化口罩，最後將客製化口罩佩戴至真人及假人頭(經3D掃描之真人頭型並以3D列印出之假人頭)上進行密合度比較。 第一部分研究結果顯示市售掃描儀之偏差值約落在0.122 mm，若比較正臉、側臉與下巴之掃描結果，正臉之掃描結果最佳，因為正臉有眼、鼻、嘴等明顯特徵。最差的為下巴，下巴不僅沒有明顯特徵也落於掃描邊界，會有最差之掃描結果。第二部分評估了掃描期間臉部變動對所造成的影響，人臉變動約會造成0.323 mm之誤差，所以若同時考量到機台本身之偏差及人臉移動所造成之影響，A廠牌之手持式掃描儀整體偏差為0.334 mm，以整體偏差來說固定式掃描儀之掃描偏差較小(0.200 mm)，然而差異僅在0.13 mm左右，第三部分研究結果指出矽膠材質本身較軟，故3D掃描及3D列印之偏差對密合度造成影響甚微，相較於市售彈性面體，在相同的上、下繫帶張力下(上繫帶張力TU=7.2 N，下繫帶張力TL=2.5 N)，真人佩戴其客製化口罩密合度值約在56372，故使用較少之繫帶張力即可達到優異之密合效果及舒適性。將口罩佩戴至假人頭(經3D掃描之真人頭型並以3D列印出之假人頭，s5)上也維持十分高之密合 (FF=15339)，然而以假人頭進行密合度測試仍為一較保守之測試方法，此外，以假人頭做為密合度測試時不需過度追求與真人相似之臉部軟硬度，使用硬度s5之矽膠即可接近真實臉部軟硬度之密合度測試結果。客製化面體必定為未來呼吸防護具的重點研發趨勢，且本研究已成功建立客製化口罩之製作流程，然而目前製作之面體偏重且製作程序複雜，仍須進一步進行改良。

Chapter 2: The tightening of the respirator straps is an efficient way to obtain an adequate face seal, the effect of strap tension on FFRs fit is seldom reported because most FFRs are available with fixed strap lengths. Therefore, the present study aimed to characterize how factors including the match between the 3-D dimensions of the respirator and the wearer's face, the strap tension exerted, the elastic properties of the subject's face skin, and the size of the FFRs and headform affecting fit performance. In the present study, the standard Chinese head-forms (small, medium, large), made of polylactic acid, were fabricated using a 3-D printer. The tensions of straps under different exertion were measured using a force gauge (Handy Digital Force Gauge, Algol, HF-1, Japan) sit on a linear sliding guide. A condensation particle counter (PortaCount, TSI Inc., St. Paul, MN, USA) was used to measure the particle concentration inside and outside the FFR. At least three replicates were conducted for each test. Based on the FFRs tested on the medium size of Chinese standard head-form, the upper strap tension (2.03~5.74 N) was basically higher than the lower strap tension (1.18~4.55 N). The higher upper strap tension was apparently designed for holding the weight of the face-piece, in addition to providing the fit. Also, the strap tension didn’t increased with increasing the weight of the FFRs. This may be the cause less respiratory protection. For a typical FFR strap, the strap tension rapidly decreased with time from 4.6 to 3.5 N in the first one hours, and, in the first 20 minutes, the tension will have the most dramatic changes. The decreasing trend lessened after the drastic change period. So, the experiment would be measured by 20 mins as a cycle. Most of the strap have a 20% attenuation in the first 20 minutes. During mannequin test, the fit factor decreased with time, which might be the main due to the lower strap tension. This strap tension decrease would create problem for estimating the workplace protection factor. Thus, straps with more stable tension properties apparently needed to provide more constant respiratory protection. The tension stability of the strap depends on the number of the Yarn count. The number of rubber wire determines the initial tension. It is recommended that the commercially available FFR’s to be used with a strap with stable tension characteristic (the higher the Yarn count number) to provide long-term seal. This study also compare the different skin hardness, the result indicate that the softer face has a greater fit. In addition, In the first 10 minutes, the fit factor will have the most dramatic changes. So, the fit testing would be perform only at the subject wearing for the mask for at least 10 mins. In the case of the same facial hardness, the larger headform has a better fit. If the mask doesn’t fit the face, then adjusting the strap tension may not meet the required. If the respirator shape has a good fit to the wearer’s face, less strap tension is needed. It is recommended that the commercially available FFR’s to be used with a strap with Adjustable length . The commercial available mask are designed for Westerner. The ideal case is that everyone has a custom made mask. In this case, least strap tension and high comfort can be achieve. Chapter 3: Commercially available masks are all fixed specification and cannot be fit to everyone's face. Donning an unsuitable mask will cause airborne contaminants leaking into the breathing zone and harm to the human body. The ideal case is that make a customized mask that perfectly fit with your face, we can used least strap tension to achieve high comfort. Therefore, this study will use 3D scanning and 3D printing systems to make customized masks. To solve the fit problems in respiratory protection The production of customized masks requires the use of 3D scanning and 3D printing technology, so, the study will divided into three parts. The first part needs to use the mannequin to evaluate the scanning bias of the commercially available scanners. Using 7 scanners to scan mannequin which prints by 3D printer, and comparing with the original image file the images by Geomagic Control X software, individually. The second part is to assess the error caused by face changes during scanning period. 10 human body were scanned with portable scanners and compared with stationary scanners. The third part is used 3D scanning system to build a 3D face model, using computer-aided design (CAD) to construct a customized mask model and then print by 3d printer. The customized mask was donning on the human head and the mannequin (3D scanning of the human head and printing its dummy head by 3D printer) to compare the fit. The first part results indicate that the deviation of the commercially available scanner is about 0.122 mm. Compare the scan results of anterior face, lateral face and inferior face. Anterior face has the least bias because it has obvious features (i.e. eyes, nose and mouth) to capture. The worst is the inferior face, it not only has no obvious features but also falls on the scanning boundary. The second part evaluated the effect of facial changes during scan was also evaluated, and the bias cause from face movement is about 0.323 mm. Taking into account the bias of the scanner and the bias cause from face movement. The overall bias of the portable scanner (brand A) is 0.334 mm. The overall scanning bias of the stationary scanner is smaller (0.200 mm). However the difference is only about 0.13 mm. The third part results indicate that the silicone material is soft enough, so the deviation of 3D scanning and 3D printing has rarely effect on the fit. Compared with the commercially available elastomeric respirator. Customized elastomeric respirators can achieve high fit (FF average: 56372. Least strap tension needed (TU: 7.2 N, TL: 2.5 N), therefore, most comfortable. Although the mannequin can also achieve high fit (FF=15339). However, it is still a more conservative test method. In addition, during mannequin (3D scanning of the human head and printing its dummy head by 3D printer) fit test, there is no need to pursue excessively facial softness. Customized mask must be a key future research and development project in respiratory protection. This research has successfully established the production process of customized masks. However, the procedure for making masks is complicated, and still need to reduce the weight of the mask in future.