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Temperature increases during dielectrophoresis (DEP) can affect the response of biological entities, and ignoring the effect can result in misleading analysis. The heating mechanism of a DEP device is typically considered to be the result of Joule heating and is overlooked without an appropriate analysis. Our experiment and analysis indicate that the heating mechanism is due to the dielectric loss (Debye relaxation). A temperature increase between interdigitated electrodes (IDEs) has been measured with an integrated micro temperature sensor between IDEs to be as high as 70 °C at 1.5 MHz with a 30  V pp applied voltage to our ultra-low thermal mass DEP device. Analytical and numerical analysis of the power dissipation due to the dielectric loss are in good agreement with the experiment data.

The liquid streams in a microchannel are hardly mixed to form laminar flow, and the mixing issue is well described by a low Reynolds number scheme. The staggered herringbone mixer (SHM) using repeated patterns of grooves in the microchannel have been proved to be an efficient passive micro-mixer. However, only a negative pattern of the staggered herringbone mixer has been used so far after it was first suggested, to the best of our knowledge. In this study, the mixing efficiencies from negative and positive staggered herringbone mixer patterns as well as from opposite flow directions were tested to investigate the effect of the micro-structure geometry on the surrounding laminar flow. The positive herringbone pattern showed better mixing efficiency than the conventionally used negative pattern. Also, generally used forward flow gives better mixing efficiency than reverse flow. The mixing was completed after two cycles of staggered herringbone mixer with both forward and reverse flow in a positive pattern. The traditional negative pattern showed complete mixing after four and five cycles in forward and reverse flow direction, respectively. The mixing effect in all geometries was numerically simulated, and the results confirmed more efficient mixing in the positive pattern than the negative. The results can further enable the design of a more efficient microfluidic mixer, as well as in depth understanding of the phenomena of positive and negative patterns existing in nature with regards to the surrounding fluids.

Dielectrophoresis, an electrokinetic technique, can be used for contactless manipulation of micro- and nano-size particles suspended in a fluid. We present a 3-D microfluidic DEP device with an orthogonal electrode configuration that uses negative dielectrophoresis to trap spherical polystyrene micro-particles. Traps with three different basic geometric shapes, i.e. triangular, square, and circular, and a fixed trap area of around 900 μm2 were investigated to determine the effect of trap shape on dynamics and strength of particle trapping. Effects of trap geometry were quantitatively investigated by means of trap stiffness, with applied electric potentials from 6 VP-P to 10 VP-P at 1 MHz. Analyzing the trap stiffness with a trapped 4.42 μm spherical particle showed that the triangular trap is the strongest, while the square shape trap is the weakest. The trap stiffness grew more than eight times in triangular traps and six times in both square and circular traps when the potential of the applied electric field was increased from 6 VP-P to 10 VP-P at 1 MHz. With the maximum applied potential, i.e. 10 VP-P at 1 MHz, the stiffness of the triangular trap was 60% and 26% stronger than the square and circular trap, respectively. A finite element model of the microfluidic DEP device was developed to numerically compute the DEP force for these trap shapes. The findings from the numerical computation demonstrate good agreement with the experimental analysis. The analysis of three different trap shapes provides important insights to predict trapping location, strength of the trapping zone, and optimized geometry for high throughput particle trapping.

We developed a method for the efficient generation of functional dopaminergic (DA) neurons from human embryonic stem cells (hESCs) on a large scale. The most unique feature of this method is the generation of homogeneous spherical neural masses (SNMs) from the hESC-derived neural precursors. These SNMs provide several advantages: (i) they can be passaged for a long time without losing their differentiation capability into DA neurons; (ii) they can be coaxed into DA neurons at much higher efficiency than that from previous reports (86% tyrosine hydroxylase-positive neurons/total neurons); (iii) the induction of DA neurons from SNMs only takes 14 days; and (iv) no feeder cells are required during differentiation. These advantages allowed us to obtain a large number of DA neurons within a short time period and minimized potential contamination of unwanted cells or pathogens coming from the feeder layer. The highly efficient differentiation may not only enhance the efficacy of the cell therapy but also reduce the potential tumor formation from the undifferentiated residual hESCs. In line with this effect, we have never observed any tumor formation from the transplanted animals used in our study. When grafted into a parkinsonian rat model, the hESC-derived DA neurons elicited clear behavioral recovery in three behavioral tests. In summary, our study paves the way for the large-scale generation of purer and functional DA neurons for future clinical applications.

The detection of body fluids has been used to identify a suspect and build a criminal case. As the amount of evidence collected at a crime site is limited, a multiplex identification system for body fluids using a small amount of sample is required. In this study, we proposed a multiplex detection platform using an Ag vertical nanorod metal enhanced fluorescence (MEF) substrate for semen and vaginal fluid (VF), which are important evidence in cases of sexual crime. The Ag nanorod MEF substrate with a length of 500 nm was fabricated by glancing angle deposition, and amino functionalization was conducted to improve binding ability. The effect of incubation time was analyzed, and an incubation time of 60 min was selected, at which the fluorescence signal was saturated. To assess the performance of the developed identification chip, the identification of semen and VF was carried out. The developed sensor could selectively identify semen and VF without any cross-reactivity. The limit of detection of the fabricated microarray chip was 10 times better than the commercially available rapid stain identification (RSID) Semen kit.

We reported an automated dielectrophoretic (DEP) tweezers-based force spectroscopy system to examine intermolecular weak binding interactions, which consists of three components: (1) interdigitated electrodes and micro-sized polystyrene particles used as DEP tweezers and probes inside a microfluidic device, along with an arbitrary function generator connected to a high voltage amplifier; (2) microscopy hooked up to a high-speed charge coupled device (CCD) camera with an image acquisition device; and (3) a computer aid control system based on the LabVIEW program. Using this automated system, we verified the measurement reliability by measuring intermolecular weak binding interactions, such as hydrogen bonds and Van der Waals interactions. In addition, we also observed the linearity of the force loading rates, which is applied to the probes by the DEP tweezers, by varying the number of voltage increment steps and thus affecting the linearity of the force loading rates. This system provides a simple and low-cost platform to investigate intermolecular weak binding interactions.

Deep brain stimulation (DBS) is a neurosurgical procedure that allows targeted circuit-based neuromodulation. DBS is a standard of care in Parkinson disease, essential tremor and dystonia, and is also under active investigation for other conditions linked to pathological circuitry, including major depressive disorder and Alzheimer disease. Modern DBS systems, borrowed from the cardiac field, consist of an intracranial electrode, an extension wire and a pulse generator, and have evolved slowly over the past two decades. Advances in engineering and imaging along with an improved understanding of brain disorders are poised to reshape how DBS is viewed and delivered to patients. Breakthroughs in electrode and battery designs, stimulation paradigms, closed-loop and on-demand stimulation, and sensing technologies are expected to enhance the efficacy and tolerability of DBS. In this Review, we provide a comprehensive overview of the technical development of DBS, from its origins to its future. Understanding the evolution of DBS technology helps put the currently available systems in perspective and allows us to predict the next major technological advances and hurdles in the field.Deep brain stimulation (DBS) is a neurosurgical procedure that allows targeted circuit-based neuromodulation and has become a standard of care in a range of movement disorders. This Review discusses the evolution and current status of DBS technology and anticipates future advances.

The clinical use of deep brain stimulation (DBS) is among the most important advances in the clinical neurosciences in the past two decades. As a surgical tool, DBS can directly measure pathological brain activity and can deliver adjustable stimulation for therapeutic effect in neurological and psychiatric disorders correlated with dysfunctional circuitry. The development of DBS has opened new opportunities to access and interrogate malfunctioning brain circuits and to test the therapeutic potential of regulating the output of these circuits in a broad range of disorders. Despite the success and rapid adoption of DBS, crucial questions remain, including which brain areas should be targeted and in which patients. This Review considers how DBS has facilitated advances in our understanding of how circuit malfunction can lead to brain disorders and outlines the key unmet challenges and future directions in the DBS field. Determining the next steps in DBS science will help to define the future role of this technology in the development of novel therapeutics for the most challenging disorders affecting the human brain.Over the past 20 years, deep brain stimulation (DBS) has transformed the treatment of movement disorders. Now, new therapeutic possibilities for DBS are emerging for other neurological and psychiatric disorders. This Review considers the clinical and scientific advances facilitated by DBS and the crucial questions, challenges and opportunities that face this technology.

Carbonization of replicated furan precursors has been proposed as a low-cost large-area method for fabricating microstructured vitreous carbon (VC) molds to glass micromolding. During the carbonization of furan precursors, large anisotropic shrinkage occurs inherently owing to thermal decomposition of the material, and this anisotropic shrinkage should be compensated to obtain the designed profiles of microcavities on the VC mold. In this study, a linear gradual shrinkage ratio model (LGSRM) was developed to predict the anisotropic shrinkage characteristics associated with the fabrication of microstructured VC molds. To verify the shrinkage model, the shape change of the VC mold according to the LGSRM was simulated with ANSYS and compared with the experimental results. To determine the coefficients of LGSRM, a finite element analysis code, in which a gradual shrinkage ratio can be assigned to each individual mesh, was developed, and the coefficients of LGSRM were selected to minimize the errors between the simulated and measured geometrical properties of the VC mold.

In patients with Parkinson’s disease, focused ultrasound ablation of the globus pallidus internus reduced motor impairment and dyskinesias at 3 months. Adverse events included dysarthria, gait disturbance, and loss of taste.