Benchtop Polymer MEMS

Abstract

Loctite photopatternable adhesives 3108, 3340, and 3525 are introduced for microelectromechanical systems (MEMS) applications. These materials are patterned within minutes by exposure to ultraviolet (UV) light followed by rinsing with a solvent; no further processing is required. Because the uncured fluid is relatively insensitive to room light, this can be done on any lab bench without the requirement for a clean room. The materials can be spin-coated to obtain films, or cast between spacers for layers up to 1 cm thick, and the cured polymers range from elastomeric to rigid. These adhesives are of interest for rapid, inexpensive fabrication of relatively low-resolution features (tens to hundreds of micrometers) by photocuring. They can alternatively be molded, like polydimethylsiloxane (PDMS), to achieve high resolution, as well as irreversibly bonded after an O 2 plasma treatment. In addition, like SU8, they can be used as molds for patterning PDMS. Initial characterization of resolution, swelling, and biocompatibility were performed. One of the polymers, 3340, can be used for packaging bioMEMS-on-complementary-metal-oxide-semiconductor (CMOS) chips, exploiting its biocompatibility and its photopatternability at thicknesses of 1500 m to cover the bond wires while exposing the chip surface. As further demonstrations of the versatility of these materials, multilevel, interconnected channel structures were fabricated with a gelatin sacrificial layer, and magnetic films were prepared, since the polymers remain patternable even with additives.[1535]

Recent Developments in Polymer MEMS

“…In addition, a number of other materials are also being used, including liquid crystal polymer (LCP), [47] liquid crystal elastomer (LCE), [48] biodegradable polymers, [49,50] functional hydrogels, [41] Paraffin, [51,52] piezoelectric polymers, fluorocarbon thin films, and conductive polymers. [53,54] The following A number of representative polymers and their MEMS applications are discussed in more detail in the following, to illustrate representative techniques and opportunities. a) PDMS Elastomer Elastomers such as PDMS and polyurethane have been used in microfluidics extensively.…”

Stretchable Electrodes with High Conductivity and Photo‐Patternability

“…In principle, the electrodes could be fabricated on virtually any surface, including large-area and curved substrates. [24] The electrode fabrication method was inspired by ionic polymer-metal composites (IPMCs). [25][26][27] In summary, fabrication begins by mixing a metal salt into a photopatternable elastomer precursor.…”

“…[14,[16][17][18][19] Methanol was chosen since it is fully miscible in water and swells 3108 by 55 %, whereas water only swells it 10 %. [24] The particular polymer used in this work was Loctite 3108 (Henkel, Inc.), but the method should be generally applicable with other materials. The samples used for electrical and mechanical measurements were fabricated by mixing tetraamineplatinum(II) chloride into the 3108, pressing the mixture between two sheets of Sealview (Norton Performance Plastics), a transparent polyolefin film to which the elastomer does not adhere, and blanket-exposing the mixture under ultraviolet light for less than a minute (365 nm from a Spectroline EN-180, power flux 5 mW cm -2 .…”

“…The samples used for electrical and mechanical measurements were fabricated by mixing tetraamineplatinum(II) chloride into the 3108, pressing the mixture between two sheets of Sealview (Norton Performance Plastics), a transparent polyolefin film to which the elastomer does not adhere, and blanket-exposing the mixture under ultraviolet light for less than a minute (365 nm from a Spectroline EN-180, power flux 5 mW cm -2 . [24] Although air was excluded in this procedure, it should be noted that curing of 3108 can be done in the presence of oxygen, [24] even though the polymer is an acrylated urethane). Spacers were used to define the 100 lm film thickness.…”

“…Without salt, this method produces a feature resolution of 310 lm in films 100 lm thick using the resolution criterion described in. [24] (Treating the mask with polydimethylsiloxane (PDMS) precursor to prevent adhesion, instead of using the 60 lm thick Sealview sheet, improves the resolution to 200 lm, but PDMS residue interferes with the chemical reduction step. [24] ) The addition of the Pt salt did not significantly change the exposure time, and the resolution only dropped somewhat due to scattering, to 350 lm (Fig.…”