Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA, 15213, USA.
Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, 15213, USA.
Macromol Rapid Commun. 2020 Mar;41(5):e1900569. doi: 10.1002/marc.201900569. Epub 2020 Jan 29.
Rapid prototyping of thin, stretchable substrates with engineered stiffness gradients at desired locations has potential impact in the robustness of skin-wearable electronics, as the gradients can inhibit cracking of interconnect and delamination of embedded electronic chips. Drop-on-demand inkjetting of thinned polydimethylsiloxane (PDMS) curing agent onto a spin-cast 80 µm-thick 20:1 (base: curing agent) PDMS substrate sets the elastic modulus of the subsequently cured film with sub-millimeter accuracy. The inkjet process creates digitally defined stiffness gradient spans as small as 100 µm for single droplets. Varying the drop density results in differences in elastic modulus of up to 80%. In jetting tests of curing agent into pure base PDMS, a continuous droplet spacing of 100 µm results in smooth lines with total widths of 1 mm and a curing agent gradient span of ≈300 µm. Release of freeform mesh elastomer microstructures by removing the uncured base after selective jetting of curing agent into pure base PDMS results in structural line width resolution down to 500 µm.
在期望位置上具有工程化的刚度梯度的薄、可拉伸基底的快速原型制作在皮肤可穿戴电子产品的鲁棒性方面具有潜在的影响，因为梯度可以抑制互连的开裂和嵌入式电子芯片的分层。按需喷墨的稀释聚二甲基硅氧烷（PDMS）固化剂到旋涂的 80 µm 厚的 20:1（基底：固化剂）PDMS 基底上，可以以亚毫米精度设置随后固化膜的弹性模量。喷墨工艺创建数字定义的刚度梯度跨度，对于单个液滴小至 100 µm。改变液滴密度会导致弹性模量差异高达 80%。在将固化剂喷射到纯基底 PDMS 中的喷射测试中，100 µm 的连续液滴间距会产生总宽度为 1 毫米且固化剂梯度跨度约为 300 µm 的光滑线条。通过在纯基底 PDMS 中选择性喷射固化剂后去除未固化的基底来释放自由形态的网眼弹性体微结构，会导致结构线宽分辨率降低到 500 µm。
