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.

中文翻译：

---

固化剂在薄PDMS上的喷墨印刷，用于局部调整机械性能。

在所需位置使用工程刚度梯度对可拉伸的薄基板进行快速原型制作，可能会对可穿戴电子设备的坚固性产生潜在影响，因为这种梯度会抑制互连的破裂和嵌入式电子芯片的分层。按需按需喷墨将稀释的聚二甲基硅氧烷（PDMS）固化剂滴涂到旋转浇铸的80 µm厚的20：1（基础：固化剂）PDMS基材上，可以以亚毫米精度设置随后固化膜的弹性模量。喷墨过程为单个液滴创建了数字定义的刚度梯度范围，该范围小至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碱PDMS中的测试中，连续的液滴间距100 µm会产生线条流畅，总宽度为1 mm，固化剂梯度跨度为≈300µm。在将固化剂选择性喷射到纯碱PDMS中后，通过除去未固化的基材来释放自由形式的网状弹性体微结构，从而使结构线的宽度分辨率降低至500 µm。