Aerobic fermentation of saccharomeyes cerevisae in a miniature bioreactor made of low cost poly(methylmethacrylate) (PMMA) and poly(Dimethylsiloxane) (PDMS) polymers

In this paper, a minibioreactor platform made of low cost polymers is presented. The minibioreactor prototype was designed as an alternative solution for carrying out microbial fermentation experiments in laboratory. The minibioreactor prototype has a working volume of 1.5 mL and was fabricated from poly(methylmethacrylate) (PMMA) and poly(dimethylsiloxane) (PDMS) polymers. Cell density was measured online whilst agitation rates and the temperature of the reactor content can be tightly controlled to desired set-point values. As proof-of-concept, various S. cerevisae fermentation experiments were conducted. In every experiment, the minibioreactor operated stably for the entire length of operation which was nearly 40 h with very minimal volume loss i.e. about 2.8 μ·h-1 at 37°C. The minibioreactor has the maximum oxygen transfer rate (OTR) of 16.6 mmol·L-1·h-1 under the agitation rate of 300 rpm. Under these conditions, cell specific growth rate as high as 0.291 h-1 was obtained. The experimental data in the minibioreactor operation was also reproducible using shake flask where similar growth profiles were attained under a similar growth conditions.

A miniature neural recording device

This paper presents a portable neural recording device for use with laboratory animals. It can detect and record neural signals from the cortical region of the brain during pre-clinical trials. The device utilizes simplified circuitry to perform signal detection, filtering, sampling, and storage. It includes analog and digital components each implemented on a separate small printed circuit board. The two printed circuit boards are then attached to one another to form the device. It is capable of uninterrupted operation for over 2 hours on a single coin battery. A bench-testing of the device was performed with pre-recorded neural signal which then injected to the input of the device to give validation of efficient operation of the device. Its amplification and filtration features have been analyzed. An overall 56 dB amplification and filtration in the frequency range of 300 Hz to 4 KHz was achieved. Sampling and storage at a reduced power and computational load is demonstrated with uninterrupted storage of the neural signal. A comparison of the input and reconstructed neural signals shows minimal variation error.

Performance evaluation of 3D printed miniature electromagnetic energy harvesters driven by air flow

As a renewable and non-polluting energy source, wind is used to produce electricity via large-diameter horizontal or vertical axis wind turbines. Such large wind turbines have been well designed and widely applied in industry. However, little attention has been paid to the design and development of miniature wind energy harvesters, which have great potential to be applied to the HVAC (heating, ventilating and air conditions) ventilation exhaust systems and household personal properties. In this work, 10 air-driven electromagnetic energy harvesters are fabricated using 3D printing technology. Parametric measurements are then conducted to study the effects of (1) the blade number, (2) its geometric size, (3) aspect ratio, presence or absence of (4) solid central shaft, (5) end plates, and (6) blade orientation. The maximum electrical power is 0.305 W. To demonstrate its practical application, the electricity generated is used to power 4 LED (light-emitting diode) lights. The maximum overall efficiency ηmax is approximately 6.59%. The cut-in and minimum operating Reynolds numbers are measured. The present study reveals that the 3D printed miniature energy harvesters provide a more efficient platform for harnessing ‘wind power’.

Numerical investigation of a trapped vortex miniature ramjet combustor

The design of a miniature ramjet combustor using gaseous methane fuel for Mach 2.5 has been conducted. The main challenges stem mainly from the insufficient space for mixing and burning, short residence time, and the flame stabilization. Impossible utilization of relatively large air-blast fuel injectors provides more difficulties for the design. The trapped vortex combustor, as a novel way of flameholding by trapping the pilot flame inside a cavity instead of exposing it to the mainstream, is selected. Three main parts are studied numerically, which include the cold flowfield characteristics, the fuel-injection schemes, and the overall combustion performance. The results show that the drag coefficient can helptodetermine the optimum cavity size for trappingastable vortex. Injecting all the fuel inthe cavity always leads to an overly fuel-rich condition, whereas injecting in front of the cavity with a momentum flux ratio q between 0.61 and 1.0 can successfully achieve stoichiometric mixing in the cavity. However, compared to nonreacting fuel mixing, the combustion performance is found to be more sensitive to the value of q. Among the cases studied, the one with a small q of about 0.61 has more intense pilot flames andshorter main combustor flames. The effectsofangled injection, upstream injection location, and the combustor length based on the found q are also investigated.