電控微流體平臺建構具顆粒之水膠用以熱與光驅動可逆可編程之四維形狀變形

Abstract

本研究提出一種建構同時具有熱致動(Heat-driven)及光驅動(Light-driven)之可逆(Reversible)可編程(Programmable)的四維形狀變形(4D shape morphing)水膠(Hydrogel)之技術，電控微流體(Electromicrofluidic, EMF)，通過此技術所建構的四維形狀變形水膠在眾多領域證明其獨特性能及優勢，例如生物醫學(Biomedical)、電子(Electronics)及航太(Astronautics)等。 運用電控微流體平臺，以介電濕潤(Electrowetting-on-dielectric, EWOD)與液體介電泳(Liquid dielectrophoresis, LDEP)驅動含有聚苯乙烯顆粒之水膠預聚物形成與設計之電極圖案相同的幾何外型，並以粒子介電泳(Particle dielectrophoresis, DEP)聚集水膠預聚物中散佈的聚苯乙烯顆粒排列成更微小尺度的電極圖案設計，隨後利用紫外光交聯水膠預聚物，由於聚苯乙烯顆粒在光交聯的過程中會吸收紫外光，使得紫外光在交聯水膠預聚物的過程中產生極大的衰弱現象，致使聚集有聚苯乙烯顆粒的區域在紫外光照射的方向有極高的交聯梯度；沒有聚苯乙烯顆粒的區域交聯梯度近乎為零，藉此控制水膠預聚物在交聯後之異向性(Anisotropy)膨脹及強度，隨後將圖案化聚苯乙烯顆粒之水膠浸至液體環境中，如水或細胞培養液等，以觸發異向性膨脹(Anisotropic swelling)的行為，使得從交聯後之二維平面結構觸發可逆自我摺疊(Reversible self-folding)以形成三維的摺紙(Origami)結構，並且通過設計的聚苯乙烯排列以創造可預測的四維形狀變形，此稱之為可逆可編程之四維形狀變形，以及通過調控液態環境的溫度，使水膠結構能夠在不同的三維結構間作變換，此稱之為熱致動。為了更快速的驅控三維結構間的變換以達成複雜的動作，例如抓取、爬行及翻滾等，利用聚苯乙烯顆粒會吸收紫外光的特性，通過照射紫外光來加熱水膠結構使其自我摺疊，稱之為光驅動，而此種水膠稱為熱與光驅動可逆可編程之四維形狀變形水膠。水膠材料為光交聯(Photocrosslink)之溫度敏感型水膠(Temperature-sensitive hydrogels)，藉由提高環境溫度使水膠結構在曝光方向之交聯梯度反應出劇烈的膨脹率梯度，以達成可逆摺疊成任意彎曲角度之四維形狀變形水膠結構。本研究所使用的水膠材料為Poly(ethylene glycol) diacrylate (PEGDA)，首先透過設計的圖案化電極，以頻率為1 kHz的電訊號操控PEGDA形成與設計之電極圖案相同的幾何外型，隨後透過更微小尺度的電極圖案，利用頻率為5 kHz的電訊號以介電泳力排列PEGDA中的聚苯乙烯顆粒。並且比較數個參數對於彎曲角度在不同溫度以及光致熱的影響。

This study propose a novel method for creating a heat and light-driven reversible 4D shape morphing hydrogel, which demonstrates its unique properties and advantages in many fields, such as biomedical, electronics and astronautics. Electromicrofluidic (EMF) platform was used to drive a hydrogel prepolymer containing polystyrene beads to form a hydrogel of patterned polystyrene beads by electrowetting-on-dielectric, liquid dielectrophoresis and particle dielectrophoresis. The polystyrene beads in the hydrogel prepolymer can control the cross-linking of hydrogel by absorbing or reflecting ultraviolet light. Thereby, Programmable swelling properties of hydrogel. The patterned polystyrene beads in the hydrogel immersed in a water or culture medium to trigger the behavior of anisotropic swelling, allowing the two-dimensional planar pattern to reversible self-folding into a three-dimensional origami structure. In order to rapid control the 4D shape morphing to achieve complex movements such as grasping, crawling and tumbling through photoheating. A heat and light-driven reversible 4D shape morphing that reversible folding at any angle is achieved by adjust ambient temperature, concentration and arrangement of the polystyrene beads. The photocrosslinkable temperature-sensitive hydrogel Poly(ethylene glycol) diacrylate (PEGDA) were employed on EMF platform.