SU-8 photoresist

FIGURE 10.4 Microphotograph of the pH ISFET with an on-chip pH meter. The whole device was coated with SU-8 photoresist using standard UV photolithography, leaving a 500 pm square well as the ISFET opening. (Reproduced from [85], with permission from Elsevier.)... 

Juodkazis S, Mizeikis V, Seet KK, Miwa M, Misawa H (2005) Two-photon lithography of nanorods in SU-8 photoresist. Nanotechnol 16 846-849... 

Microchannels have also been directly patterned on SU-8 photoresist [232-234,892]. Multilevel structures were fabricated using the SU-8 photoresist [232]. In another report, the SU-8 photoresist was spun (1250 rpm for 30 s) on an ITO-coated glass plate, which was first treated by an 02 plasma to increase the adhesion of SU-8 on ITO. The photoresist channel was of ribbon-like structure with triangular ends (40 pm height, 10 mm width and 90 mm length). The channel was bonded by hot-pressing to another ITO glass on top of the photoresist structures [892]. SU-8 photoresists have also been used to create multilayered... 

Ultra-thick microfluidic stmctures (up to 1.5 mm high) were fabricated using SU-8 photoresist. Instead of using a spin-coater, a constant-volume injection method was used to apply thick photoresist for patterning [237]. 

Galvanostatic measurements on the C-MEMS array in a half-cell with lithium as both the counter and reference electrode [32] show a large irreversible capacity loss on first discharge followed by good cycling properties consistent with the behavior of conventional bulk coke electrodes. The lithium capacity normalized to the foot print area of the electrode array is 0.125 mAhcm". This value is nearly twice that of an unpattemed pyrolyzed film of SU-8 photoresist [32], The higher capacity is due to the greater active volume, contributed by the carbon posts over the footprint area (Fig. 2.10). 

Figure 15.3 Cell clinics constructed using PPy hinges to seal a 100 x 100 gm microcavity (A) schematic with PPy hinge and (B) picture of an open and closed cell clinic formed in a 20 pm thick SU-8 photoresist on a transparent class substrate. (Reprinted with permission from Science, Microfabricating conjugated polymer actuators by E. W. Jager, E. Smela and O. Inganas, 290 5496, 1540-1545. Copyright (2000) American Association for the Advancement of Science)...

C. Lin, G. Lee, B. Chang, and G. Chang, A new fabrication process for ultra-thick microfluidic microstructures utilizing SU-8 photoresist. Journal of Micromechanics and Microengineering, 12(5), 590-597, 2002. 

Cui Z, Jenkins DWK, Schneider A, Mcbride G (2001) Profile control of Su-8 photoresist using different radiation sources. SPIE 4407 119-125... 

Microdialysis, Fig. 5 (a) SEM image of a polycarbonate microdiaiysis membrane bonded onto microllnidic channels formed in SU-8 photoresist (Image taken from Hsieh and Zahn [13]). (b) Two-cranpartment system with integrated condnctance sensing electrodes. The reservoir and perfusion flow channels are separated by a bonded... 

To characterize the devices and use them for applications like cancer stem cell sorting and blood cell sorting, standard soft lithography was used to fabricate devices in PDMS. An SU-8 photoresist master was used to cast PDMS (polydimethylsiloxane). The patterned PDMS was sealed with T73 glass slide using corona discharge. The patterned PDMS was sealed with... 

Nanosubstrate, rather than particle, approaches have been utilized in a handful of experiments [33, 34]. HCCA has been crosslinked to SU-8 photoresist polymer via cationic photoiortization, forming a hydrophobic surface. When aqueous sample droplets are applied to this support, surface tension during evaporation essentially concentrates the samples and thus improves the analysis sensitivity [34]. Another engineering approach has been to pre-deposit CHCA matrix crystals by vacuum sublimation onto an ultra-phobic surface. The resultant disposable chips contain an array of matrix spots which concentrate analytes from aqueous matrixes during the drying process. The approach has been applied to the quantitation of drug compounds in biofluids such as serum or urine [31]. 

The very first flow focusing device was developed by Stone and coworkers [11] and was used for the emulsification of water in silicone oil. The geometry of this device is depicted in Figure 18.7 and was obtained after replication of a positive relief of the microchannels patterned in SU-8 photoresist. The authors named this FFD a microfluidic flow focusing device (MFFD). A few years after the development of this microsystem, Kumacheva and coworkers [12] used an MFFD (Figure 18.7, top left) made out of PDMS or polyurethane (PU) for the emulsification and polymerization of several multifunctional acrylates ethylene glycol dimethacrylate (EGDMA),... 

Gracias et al. used melting of polymer, which form a droplet and forces patterned polymer films to fold. This was demonstrated on the example of patterned SU-8 photoresist-polycaprolactone film, which irreversibly folds at 60 °C [31] due to melting of polycaprolactone (Fig. 1.4). In order to reduce the transition temperature and make film more suitable bio-related applications, Gracais et al. used photoresist hinges which are sensitive to temperature around 40 °C [32]. The metal-polymer grippers irreversibly fold in response to temperature as well. 

A popular resist for MEMS processing is SU-8 [US Patent No. 4882245 (1989)]. This is a negative tone resist and is commonly applied as a layer, tens of micrometres in thickness. SU-8 was developed by Shell Chemicals and uses epoxy-based chemistry. Microchem [www.microchem.com] is one of the companies that now holds the licence for production and sale of SU-8 photoresists. 

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