Three‐Dimensional Assembly of Polymer Microstructures at Low Temperatures

Abstract

ing sphere [28] purged with flowing nitrogen and the sample was excited at 325 nm and excitation power of 0.2 mW. Photoluminescence transient decays were measured by a time-correlated singlephoton counting (TCSPC) system. Excitation was at~390 nm from a pulsed laser diode (Picoquant) giving 10 pJ pulse ±1. The apparatus response function was~350 ps (full width at half maximum) on its fastest scale. All measurements were performed at room temperature. Films were kept in a vacuum of < 10 ±3 mbar during measurements. The decay kinetics were fitted by a sum of exponential functions: I(t) = A 1 exp(±t/s 1 ) + A 2 exp(±t/s 2 ) with A and s as the pre-exponential factor and excited state lifetime respectively. The quality of the fits was confirmed by random distribution of the residuals.For EL characterization OLEDs were prepared by spin-coating the electroluminescent layers, consisting of 20 wt.-% of each dendrimer blended into CBP, onto transparent indium tin oxide (ITO) anodes (20 X/square) that had been oxygen-plasma treated in an Emitech K1050X plasma unit. The solution concentration was 20 mg mL ±1 in chloroform and the spin speed 2000 rpm for 1 min. The films formed were of good quality as determined by optical microscopy and surface profilometry. After spin-coating, the samples were placed into a high vacuum chamber and an electron transport layer (ETL) and cathode materials were sequentially evaporated. The electron transport layer was 1,3,5-tris(2-N-phenylbenzimidazolyl)benzene (TPBI), and was evaporated at 0.05 nm s ±1, and the cathode comprised lithium fluoride (0.4 nm), calcium (12 nm), and aluminum (50 nm) layers evaporated at 0.5 nm s ±1 . Electrical and optical measurements of all OLED devices were made under high vacuum (10 ±5 mbar) at room temperature. The effective area of each emitting diode was 6 mm 2 . The EL spectra were recorded with an Oriel MS125 Spectrograph coupled to a CCD detector (spectral resolution~1 nm). Current±voltage and brightness±voltage analyses were performed using a Keithley 2400 Source meter and a Keithley 2000 meter (employing a calibrated silicon photodiode), respectively. Luminance was also measured using a calibrated Minolta LS-100 luminance meter. External quantum efficiencies were calculated from the luminance, current density, and emission spectrum of each device assuming Lambertian emission.

Packaging of microfluidic chips via interstitial bonding technique

“…The lap shear tests, ASTM 3163(01), were conducted using the modified joint geometry to characterize the bonding strength [30]. Two specimens, each 1.5 mm thick, 12.7 mm wide, and 50 mm long were bonded together with the overlapped area 12.7 mm612.7 mm.…”

Polymer Nanoengineering for Biomedical Applications

“…The nanostructures, including surface roughness, are well preserved and the bond strength is the same as the bulk material. 136 Although there are other methods to bond nanoscale polymer features. 13,14,18,49,53,86,119,127 gas-assisted bonding is the most affordable and probably the only biologically benign and sterile method, in particular for simultaneous assembly of a large number of nanostructures.…”

Low-Pressure Carbon Dioxide Enhanced Polymer Chain Mobility below the Bulk Glass Transition Temperature

“…[14][15][16] In this study, we investigate the enhancement of chain mobility by low-pressure CO 2 below the bulk T g , the confining effects of substrates on polymers, and the effects of CO 2 and substrate confinement on polymer chain mobility. The ultimate goal is to facilitate polymer nanofabrication at low temperatures using low-pressure CO 2 as a processing aid.…”