Morphological Influence of Solution-Processed Zinc Oxide Films on Electrical Characteristics of Thin-Film Transistors

We report on the morphological influence of solution-processed zinc oxide (ZnO) semiconductor films on the electrical characteristics of ZnO thin-film transistors (TFTs). Different film morphologies were produced by controlling the spin-coating condition of a precursor solution, and the ZnO films were analyzed using atomic force microscopy, X-ray diffraction, X-ray photoemission spectroscopy, and Hall measurement. It is shown that ZnO TFTs have a superior performance in terms of the threshold voltage and field-effect mobility, when ZnO crystallites are more densely packed in the film. This is attributed to lower electrical resistivity and higher Hall mobility in a densely packed ZnO film. In the results of consecutive TFT operations, a positive shift in the threshold voltage occurred irrespective of the film morphology, but the morphological influence on the variation in the field-effect mobility was evident. The field-effect mobility in TFTs having a densely packed ZnO film increased continuously during consecutive TFT operations, which is in contrast to the mobility decrease observed in the less packed case. An analysis of the field-effect conductivities ascribes these results to the difference in energetic traps, which originate from structural defects in the ZnO films. Consequently, the morphological influence of solution-processed ZnO films on the TFT performance can be understood through the packing property of ZnO crystallites

Demonstrating SleepGuru: Personalized Sleep Planning System for Real-life Actionability and Negotiability

Widely-accepted sleep guidelines advise people about regular bedtimes and sleep hygiene. However, these standard guidelines are often little applicable to our real-life full of duty and responsibility. We propose SleepGuru, an individually actionable sleep planning system featuring one’s real-life compatibility and extended forecast. Leveraging wearable activity trackers and commercial mobile calendars, SleepGuru computes individually actionable multi-day sleep schedules that optimize the sleep timings and the user’s alertness levels subject to one’s real-life constraints. SleepGuru provides individual predictions and adjustability through a mobile-friendly user interface backed by a cloud-side optimization engine.1

SleepGuru: Personalized Sleep Planning System for Real-life Actionability and Negotiability

Widely-accepted sleep guidelines advise regular bedtimes and sleep hygiene. An individual’s adherence is often viewed as a matter of self-regulation and anti-procrastination. We pose a question from a different perspective: What if it comes to a matter of one’s social or professional duty that mandates irregular daily life, making it incompatible with the premise of standard guidelines? We propose SleepGuru, an individually actionable sleep planning system featuring one’s real-life compatibility and extended forecast. Adopting theories on sleep physiology, SleepGuru builds a personalized predictor on the progression of the user’s sleep pressure over a course of upcoming schedules and past activities sourced from her online calendar and wearable fitness tracker. Then, SleepGuru service provides individually actionable multi-day sleep schedules which respect the user’s inevitable real-life irregularities while regulating her week-long sleep pressure. We elaborate on the underlying physiological principles and mathematical models, followed by a 3-stage study and deployment. We develop a mobile user interface providing individual predictions and adjustability backed by cloud-side optimization. We deploy SleepGuru in-the-wild to 20 users for 8 weeks, where we found positive effects of SleepGuru in sleep quality, compliance rate, sleep efficiency, alertness, long-term followability, and so on.1

Tailorable Degradation of pH-Responsive All Polyether Micelles via Copolymerisation with Varying Acetal Groups

Smart drug delivery in a site-specific and time-controlled manner is critical for reducing the side effects of the drug while maximizing the therapeutic efficacy. Herein, we describe an efficient approach to control the degradation kinetics of polyether micelles under acidic conditions using random copolymers of functional epoxide monomers bearing different acetal groups. The amphiphilic block copolymers, poly(ethylene glycol)-block-poly(ethoxyethyl glycidyl ether-co-tetrahydropyranyl glycidyl ether)s (PEG-b-P(EEGE-co-TGE))s, are synthesized by the anionic ring-opening polymerisation of the pH-responsive novel epoxide monomers ethoxyethyl glycidyl ether (EEGE) and tetrahydropyranyl glycidyl ether (TGE) in varying ratios. The random block copolymers are carefully characterized by 1H NMR, GPC, and DSC and the copolymerisation kinetics are evaluated using in situ 1H NMR analysis. The critical micelle concentrations, loading efficiencies, and size distributions of the copolymer micelles show a saturation point over a critical TGE ratio. Interestingly, the degradation and subsequent release kinetics of the micelles under acidic conditions are remarkably different when the composition of the acetal groups is varied. The superior biocompatibility coupled with the highly tailorable release kinetics is anticipated to lead to a versatile platform for smart drug delivery systems