Printable elements

For many applications, it is desirable that the adhesive layer accept printable elements readily in its fully cured state. This characteristic usually requires the layer to be soft in its cured form. Adhesive thin films composed of low-modulus PDMS elastomer meet this requirement well18 and can guide transfer of elements to a target quickly (without exposure to heat or light). Surprisingly, the direction of transfer can be well defined even when the composition of the adhesive is identical to that of the stamp. Successful transfer is thus determined by several factors surface chemistry, conformability (modulus), geometrical/mechanical factors (e.g., adhesive film thickness), and others. 

Printable elements, especially those prepared by top-down methods, are often prepared such that they are attached to the mother substrate by tethers and anchoring structures that keep the otherwise freestanding elements in place. To separate elements from the mother substrate in the retrieval step, stamps must successfully break these tethers, which are typically composed of the same inorganic material as the elements. This process often requires careful design of the elements and tethers such that the elements separate by well-controlled and reliable fracture. Simple fracture theory63 points to several important factors that lead to easy fracture, notably the presence of cracks in the inorganic material and the geometry of those cracks. 

Interest in the synthesis of decaphenylcyclopentasilane has been renewed in recent times [115] as it still is the commonly used precursor for the synthesis of cyclopen-tasilane [116], which has become a valuable material for solution-phase processing to obtain printable devices based on elemental silicon [117]. 

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