Wensheng Hou

A high-throughput dielectrophoresis-based cell electrofusion microfluidic device†

A high‐throughput cell electrofusion microfluidic chip has been designed, fabricated on a silicon‐on‐insulator wafer and tested for in vitro cell fusion under a low applied voltage. The developed chip consists of six individual straight microchannels with a 40‐μm thickness conductive highly doped Si layer as the microchannel wall. In each microchannel, there are 75 pairs of counter protruding microelectrodes, between which the cell electrofusion is performed. The entire highly doped Si layer is covered by a 2‐μm thickness aluminum film to maintain a consistent electric field between different protruding microelectrode pairs. A 150‐nm thickness SiO2 film is subsequently deposited on the top face of each protruding microelectrode for better biocompatibility. Owing to the short distance between two counter protruding microelectrodes, a high electric field can be generated for cell electrofusion with a low voltage imposed across the electrodes. Both mammalian cells and plant protoplasts were used to test the cell electrofusion. About 42–68% cells were aligned to form cell–cell pairs by the dielectrophoretic force. After cell alignment, cell pairs were fused to form hybrid cells under the control of cell electroporation and electrofusion signals. The averaged fusion efficiency in the paired cells is above 40% (the highest was about 60%), which is much higher than the traditional polyethylene glycol method (<5%) and traditional electrofusion methods (∼12%). An individual cell electrofusion process could be completed within 10 min, indicating a capability of high throughput.

Effect of linear surface-charge non-uniformities on the electrokinetic ionic-current rectification in conical nanopores

The electrokinetic ionic-current rectification in a conical nanopore with linearly varying surface-charge distributions is studied theoretically by using a continuum model composed of a coupled system of the Nernst-Planck equations for the ionic-concentration field and the Poisson equation for the electric potential in the electrolyte solution. The numerical analysis includes the electrochemistry inside reservoirs connected to the nanopore, neglected in previous studies, and more precise accounts of the ionic current are provided. The surface-charge distribution, especially near the tip of the nanopore, significantly affects the ionic enrichment and depletion, which, in turn, influence the resulting ionic current and the rectification. It is shown that non-uniform surface-charge distribution can reverse the direction, or sense, of the rectification. Further insights into the ionic-current rectification are provided by discussing the intriguing details of the electric potential and ionic-concentration fields, leading to the rectification. Rationale for future studies on ionic-current rectification, associated with other non-uniform surface-charge distributions and electroosmotic convection for example, is discussed.

Electric Field Simulation of High-throughput Cell Electrofusion Chip

Abstract The electric field profile within a cell-fusion chip is of great significance for cell manipulation and cell-fusion efficiency, which is a main factor considered in chip design. This profile is mainly decided by the channel geometry and microelectrode structure. In the cell-fusion chip, the microelectrode array which was composed of a large number of microelectrodes was used to obtain high cell-fusion efficiency. Its simulation was difficult because there were many electrodes, complex channel geometry and microelectrode structure on this chip. ANSYS software was used in this study to simulate the electric field profile (strength and gradient) in the cell fusion chip. Comparison between different designs, the layout of electrodes was optimized and an interdigital, pectinate, rectangular microelectrode arrays were selected as the main components of the cell-electrofusion chip. In the preliminary experiments on this chip prototype, many plant protoplasts could be fused simultaneously. The fusion efficiency (about 40%) was much larger than those in traditional chemical induced fusion (

The study of a remote-controlled gastrointestinal drug delivery and sampling system.

A micromachined capsule based on microelectromechanical systems (MEMS) technology is introduced in this paper. It is an effective tool for diagnosing and treating gastrointestinal diseases. The microcapsule can carry out real-time drug release and the gastrointestinal fluid sampling in the gastrointestinal tract. According to the structural and metabolic characters of the gastrointestinal tract, the configuration of the microcapsule was designed as a cylinder. This nondigestible oral device can smoothly pass through the gastrointestinal tract for drug delivery and liquid sampling. The working mechanism of the capsule was the mechanic movement mode of a piston, which was regulated through a MEMS calorific element. The action of drug delivery and gastrointestinal fluid sampling in the gastrointestinal tract was performed wirelessly. The remote control device can be connected with a computer through a serial port (RS-232), and it can be used in telemedicine applications. Some experimental research has been carried out to validate the design. The experimental results indicated that the microcapsule can achieve drug delivery and liquid sample reliably.

A New Method of Synthesizing Black Birnessite Nanoparticles: From Brown to Black Birnessite with Nanostructures

A new method for preparing black birnessite nanoparticles is introduced. The initial synthesis process resembles the classical McKenzie method of preparing brown birnessite except for slower cooling and closing the system from the ambient air. Subsequent process, including wet-aging at for 48 hours, overnight freezing, and lyophilization, is shown to convert the brown birnessite into black birnessite with complex nanomorphology with folded sheets and spirals. Characterization of the product is performed by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), thermogravimetric analysis (TGA), and adsorption (BET) techniques. Wet-aging and lyophilization times are shown to affect the architecture of the product. XRD patterns show a single phase corresponding to a semicrystalline birnessite-based manganese oxide. TEM studies suggest its fibrous and petal-like structures. The HRTEM images at 5 and 10 nm length scales reveal the fibrils in folding sheets and also show filamentary breaks. The BET surface area of this nanomaterial was found to be 10.6 /g. The TGA measurement demonstrated that it possessed an excellent thermal stability up to . Layer-structured black birnessite nanomaterial containing sheets, spirals, and filamentary breaks can be produced at low temperature () from brown birnessite without the use of cross-linking reagents.

A Micropower Miniature Piezoelectric Actuator for Implantable Middle Ear Hearing Device

This paper describes the design and development of a small actuator using a miniature piezoelectric stack and a flextensional mechanical amplification structure for an implantable middle ear hearing device (IMEHD). A finite-element method was used in the actuator design. Actuator vibration displacement was measured using a laser vibrometer. Preliminary evaluation of the actuator for an IMEHD was conducted using a temporal bone model. Initial results from one temporal bone study indicated that the actuator was small enough to be implanted within the middle ear cavity, and sufficient stapes displacement can be generated for patients with mild to moderate hearing losses, especially at higher frequency range, by the actuator suspended onto the stapes. There was an insignificant mass-loading effect on normal sound transmission (<;3 dB) when the actuator was attached to the stapes and switched off. Improved vibration performance is predicted by more firm attachment. The actuator power consumption and its generated equivalent sound pressure level are also discussed. In conclusion, the actuator has advantages of small size, lightweight, and micropower consumption for potential use as IMHEDs.

Assessing the Therapeutic Effect of 630 nm Light-Emitting Diodes Irradiation on the Recovery of Exercise-Induced Hand Muscle Fatigue with Surface Electromyogram

This paper aims to investigate the effect of light emitting diode therapy (LEDT) on exercise-induced hand muscle fatigue by measuring the surface electromyography (sEMG) of flexor digitorum superficialis. Ten healthy volunteers were randomly placed in the equal sized LEDT group and control group. All subjects performed a sustained fatiguing isometric contraction with the combination of four fingertips except thumb at 30% of maximal voluntary contraction (MVC) until exhaustion. The active LEDT or an identical passive rest therapy was then applied to flexor digitorum superficialis. Each subject was required to perform a re-fatigue task immediately after therapy which was the same as the pre-fatigue task. Average rectified value (ARV) and fractal dimension (FD) of sEMG were calculated. ARV and FD were significantly different between active LEDT and passive rest groups at 20%–50%, 70%–80%, and 100% of normalized contraction time (). Compared to passive rest, active LEDT induced significantly smaller increase in ARV values and decrease in FD values, which shows that LEDT is effective on the recovery of muscle fatigue. Our preliminary results also suggest that ARV and FD are potential replacements of biochemical markers to assess the effects of LEDT on muscle fatigue.

Handgrip Force Estimation Based on a Method Using Surface Electromyography (sEMG) of Extensor Carpi Radialis Longus

Both flexor and extensor muscle activated together when hand-grip task conducted, but there is little work that attempts to specifically investigate the relationship of the hand-grip force level and the EMG activity of extensor muscles. The present study was designed to investigate the correlation between hand-grip force level and sEMG of ECRL (extensor carpi radialis longus, ECRL). A pseudo-randomized sequence of hand-grip tasks with some specific force ranges has been defined for calibration. Eight subjects (university students, five males and three females) were recruited to conduct both calibration trials and voluntary trials. EMG signals have been preprocessed with RMS (root-mean-square) method, after which EMG signals are normalized with amplitude value of MVC-related EMG. With data regression of calibration trials, a linear model has been developed to correlate the handgrip force output with sEMG activities of ECRL and this linear model then is employed to estimate the hand-grip force production of voluntary trials. The root-mean-square-error (RMSE) of the estimated force output for all the voluntary trials are statistically compared in different force ranges. The results indicate that the linear model is useful to estimate the handgrip force based on the EMG activities of forearm extensor muscle, and the accuracy of this model is dependent on the force levels. That is the linear model can provide best estimation in moderate force range (30%-50% MVC), while the force prediction error tends to be large for weak force (20%-30% MVC) or strong force (50%-80% MVC).

A STUDY OF MODELS FOR HANDGRIP FORCE PREDICTION FROM SURFACE ELECTROMYOGRAPHY OF EXTENSOR MUSCLE

Force production involves the coordination of multiple muscles, and the produced force levels can be attributed to the electrophysiology activities of those related muscles. This study is designed to explore the activity modes of extensor carpi radialis longus (ECRL) using surface electromyography (sEMG) at the presence of different handgrip force levels. We attempt to compare the performance of both the linear and nonlinear models for estimating handgrip forces. To achieve this goal, a pseudo-random sequence of handgrip tasks with well controlled force ranges is defined for calibration. Eight subjects (all university students, five males, and three females) have been recruited to conduct both calibration and voluntary trials. In each trial, sEMG signals have been acquired and preprocessed with Root–Mean–Square (RMS) method. The preprocessed signals are then normalized with amplitude value of Maximum Voluntary Contraction (MVC)-related sEMG. With the sEMG data from calibration trials, three models, Linear, Power, and Logarithmic, are developed to correlate the handgrip force output with the sEMG activities of ECRL. These three models are subsequently employed to estimate the handgrip force production of voluntary trials. For different models, the Root–Mean–Square–Errors (RMSEs) of the estimated force output for all the voluntary trials are statistically compared in different force ranges. The results show that the three models have different performance in different force ranges. Linear model is suitable for moderate force level (30%–50% MVC), whereas a nonlinear model is more accurate in the weak force level (Power model, 10%–30% MVC) or the strong force level (Logarithmic model, 50%–80% MVC).

Characterization of finger isometric force production with maximum power of surface electromyography

Fingers action has been controlled by both intrinsic and extrinsic hand muscles. Characterizing the finger action with the activations of hand muscles could be useful for evaluating the neuromuscular control strategy of fingers motor functions. This study is designed to explore the correlation of isometric fingertip force production and frequency-domain features of surface electromyography (sEMG) recorded on extrinsic hand muscles. To this end, 13 subjects (five male and eight female university students) have been recruited to conduct a target force-tracking task. Each subject is required to produce a certain level of force with either the index or middle fingertip to match the pseudo-random ordered target force level (4N, 6N, or 8N) as accurate as possible. During the finger force production process, the sEMG signals are recorded on two extrinsic hand muscles: flex digitorum superficials (FDS) and extensor digitorum (ED). For each sEMG trail, the power spectrum is estimated with the autoregressive (AR) model and from which the maximum power is obtained. Our experimental results reveal three findings: (1) the maximum power increases with the force level regardless of the force producing finger (i.e. index or middle) and the extrinsic hand muscle (i.e. FDS or ED). (2) The sEMG maximum power of index finger is significantly lower than that of the middle finger under the same force level and extrinsic hand muscle. (3) No significant difference can be found between the maximum powers of FDS and ED. The results indicate that the activations of the extrinsic muscles are affected by both the force level and the force producing finger. Based on our findings, the sEMG maximum power of the extrinsic hand muscles could be used as a key parameter to describe the fingers actions.